Amiodarone - Pharmaceutical Information, Clinical Trials, Detailed Pharmacology, Toxicology.
Россия
  • Россия
  • Украина

Amiodarone - Scientific Information

Manufacture: Fresenius Kabi USA, LLC
Country: Canada
Condition: Arrhythmia, Atrial Fibrillation, Atrial Flutter, Chagas disease (Trypanosomiasis), Ventricular Tachycardia, Ventricular Fibrillation, WPW Syndrome (Wolff-Parkinson-White Syndrome)
Class: Antiarrhythmic agents
Ingredients: Amiodarone Hydrochloride, Benzyl Alcohol as preservative, Polysorbate 80 and Water for Injection

Pharmaceutical Information

Drug Substance

Proper name: Amiodarone Hydrochloride
Chemical name: 2-butyl-3-benzofuranyl 4-(2-diethylaminoethoxy)-3,5-diiodophenyl methanone hydrochloride
Molecular formula and molecular mass: C25H29I2NO3·HCl
681.78 g/mol
Structural formula:



Physicochemical properties:
Physical Description: White to almost white fine crystalline powder
Solubility (at 25 °C): Water: 0.25 mg/mL
Ethanol (96%): 30 mg/mL
Ethanol (100%): 13 mg/mL
Hexane: 0.0015 mg/mL
Methylene Chloride: 294 mg/mL
Methanol: 114 mg/mL
pKa Value: 6.64
Melting Point: 159 0C - 163 0C

Clinical Trials

Table 1 – CLINICAL TRIALS SUMMARY
Study Drug/
Route of
Administration
Study Type Dose Patients/
Indication
Results
I.V. amiodarone Placebo-controlled Approximately 1500 mg/day I.V. amiodarone administered using 2- and 3-stage infusion regimens Patients with supraventricular arrhythmias and 2- to 3-consecuive-beat ventricular arrhythmias Rapid onset of antiarrhyth-mic activity. In patients with complex ventricular arrhythmias, amiodarone therapy reduced episodes of VT by 85%.
I.V. amiodarone Pharmacokinetic/ pharmacodynamic study evaluating rapid I.V. loading Approximately 1500 mg/day I.V. amiodarone administered using 2- and 3-stage infusion regimens Patients with recurrent, refrac-tory VT/VF Rapid onset of antiarrhyth-mic activity. In patients with complex ventricular arrhythmias, amiodarone therapy reduced episodes of VT by 85%.
I.V. amiodarone Two randomized, parallel, dose-response trials Approximately 125, 500 (one trial only) or 1000 mg over the first 24 hours; The dose regimen consisted of an initial rapid loading infusion, followed by a slower 6-hour loading infusion, and then an 18-hour maintenance infusion; the maintenance infusion was continued up to hour 48. Acute effective-ness in suppres-sing recurrent VF or hemodynam-ically unstable VT in patients with at least two episodes of VF or hemodynamically unstable VT in the preceding 24 hours Prospectively defined primary efficacy end point: rate of VT/VF episodes per hour. Median rate was 0.02 episodes per hour in patients receiving the high dose and 0.07 episodes per hour in patients receiving the low dose, or approximately 0.5 versus 1.7 episodes per day (p = 0.07, 2-sided). Signif-icantly fewer supplemental infusions were given to patients in the high-dose group. In one study, the time to first episode of VT/VF was significantly prolonged. Mortality was not affected.

A placebo-controlled study of i.v. amiodarone in patients with supraventricular arrhythmias and 2 to 3-consecutive-beat ventricular arrhythmias, and a pharmacokinetic/pharmacodynamic study evaluating rapid i.v. loading in patients with recurrent, refractory ventricular tachycardia (VT)/ ventricular fibrillation (VF) have shown rapid onset of antiarrhythmic activity well before significant blood levels of desethylamiodarone (DEA) were present; approximately 1500 mg/day of i.v. amiodarone were administered using 2- and 3-stage infusion regimens. In the patients with complex ventricular arrhythmias, including sustained and nonsustained VT, amiodarone therapy reduced episodes of VT by 85%.

The acute effectiveness of intravenous amiodarone in suppressing recurrent VF or hemodynamically unstable VT is supported by two randomized, parallel, dose-response studies of approximately 300 patients each. In these studies, patients with at least two episodes of VF or hemodynamically unstable VT in the preceding 24 hours were randomly assigned to receive doses of approximately 125 or 1000 mg over the first 24 hours, an 8-fold difference. In one study, a middle dose of approximately 500 mg was evaluated. The dose regimen consisted of an initial rapid loading infusion, followed by a slower 6-hour loading infusion, and then an 18-hour maintenance infusion. The maintenance infusion was continued up to hour 48. Additional supplemental infusions of 150 mg were given for “breakthrough” VT/VF more frequently to the 125-mg dose group, thereby considerably reducing the planned 8-fold differences in total dose to 1.8- and 2.6-fold, respectively, in the two studies.

The prospectively defined primary efficacy end point was the rate of VT/VF episodes per hour. For both studies, the median rate was 0.02 episodes per hour in patients receiving the high dose and 0.07 episodes per hour in patients receiving the low dose, or approximately 0.5 versus 1.7 episodes per day (p = 0.07, 2-sided, in both studies). In one study, the time to first episode of VT/VF was significantly prolonged (approximately 10 hours in patients receiving the low dose and 14 hours in patients receiving the high dose). In both studies, significantly fewer supplemental infusions were given to patients in the high-dose group. Mortality was not affected in these studies; at the end of double-blind therapy or after 48 hours, all patients were given open access to whatever treatment (including Amiodarone IV) was deemed necessary.

Detailed Pharmacology

In anaesthetized dogs, amiodarone, in two separate single-dose studies of 2.5, 5, and 10 (n = 7/dose), and 10 (n = 10) and 20 (n = 5) mg/kg i.v., caused a decrease in cardiac contractility (maximal at 10 mg/kg), systemic pressure and heart rate, and an increase in left ventricular end-diastolic pressure.

Direct injection of amiodarone (10 to 1000 μg) into the anterior descending branch of the left coronary artery of isolated, blood-perfused, dog ventricular muscle (n = 8) electrically-paced at 1.5 to 2.0 Hz, produced dose-dependent decreases of left ventricular dp/dt and developed tension to a maximum decrease of 50%.

In anaesthetized dogs, single intravenous doses of 3, 5, or 10 mg/kg increased coronary blood flow and decreased coronary artery resistance, left ventricular work, heart rate, total peripheral vascular resistance, and myocardial oxygen consumption in a dose-dependent manner.

In anaesthetized dogs, single intravenous doses of amiodarone, 10 mg/kg, reduced heart rate an additional 23% after it had been maximally reduced by intravenous propranolol and atropine. Under similar conditions, amiodarone reduced an isoprenaline-mediated increase in heart rate. Further combinations of single doses of intravenous amiodarone with intravenous propranolol, with intravenous glucagon and with intraperitoneal reserpine led the investigators to conclude that the observed anti-adrenergic actions of amiodarone were not mediated by competitive blockade of beta-adrenoceptors.

In 19 anaesthetized dogs administered single, rapid, intravenous doses of amiodarone, percutaneously-introduced intracardiac probes measured the monophasic action potentials (MAP) of right atria and ventricles, bundle of His potentials, and atrial and ventricular stimulation. Under the conditions of the experiment, the peak activity of amiodarone was found between the fifth and the tenth minutes. The rate of discharge of the sinus node was lowered by 36%. At the atrial level, the duration of the MAP was increased by 9% and its dv/dt was lowered slightly, the total refractory period was increased by 22%, the effective refractory period was increased by 27%, the functional refractory period was increased by 19%, the ratio of the length of the effective period/duration of the MAP became slightly greater than unity, conduction facilitation disappeared, and the period of slow conduction increased. In the AV node, the AH interval increased by 44% under normal rhythm, while atrial stimulation at 200/msec resulted in conversion to total AV block in more than half of the cases. The potential of the bundle of His and the HV interval were not altered. At the ventricular level, the duration of the monophasic action potential increased by 25%, its dv/dt decreased slightly, the total refractory period increased by 8%, and the effective refractory period increased by 14%.

Amiodarone, 20 mg/kg, given daily for 6 weeks intraperitoneally to rabbits, had no effect on the resting potential or action potential height and only a small effect on the maximum rate of depolarization of isolated rabbit atrial or ventricular muscle fibres as shown by intracellular recording. It caused a considerable prolongation of the action potential in both tissues.

Using a microelectrode technique, the action of amiodarone (1.5 x 10-5 M) on the sinus node activity of spontaneously-beating, isolated right atria of rabbits was discovered to consist of a significant increase of the action potential duration and a decrease of the slope of diastolic depolarization, both effects leading to a reduction in the sinus rate.

In in vitro experiments using voltage clamp conditions by means of the double sucrose gap technique in both frog atrial and ferret ventricular fibres, an aqueous solution of amiodarone (2.10-4 to 2.10-5 M) decreased outward K+ - mediated currents and decreased reactivation of inward currents.

In an experiment involving the simultaneous daily administration by intraperitoneal injection to live rabbits (n = 5) for a period of 3 weeks (beginning at week 4) of 5 μg of thyroxine (assumed normal daily thyroxine requirement for these rabbits: approximately 7 μg/day) and 20 mg/kg of amiodarone (for a period of 6 weeks), the prolongation by amiodarone of the action potential of isolated rabbit atria and ventricular strips was prevented. Treatment of similar rabbits (n = 5) with 10 mg/kg of potassium iodine (equivalent to the iodine content of 20 mg/kg of amiodarone) given daily, intraperitonealy, for 6 weeks had no effect upon cardiac action potential duration. It was concluded by the investigators conducting the rabbit tissue experiments that amiodarone had effects on cardiac action potentials similar to those which occur after thyroidectomy.

Amiodarone has been shown to exhibit antiarrhythmic activity in several experimental animal models. At a single intravenous dose of 5 mg/kg, amiodarone suppressed multifocal ventricular ectopic beats induced by the intravenous injection of epinephrine in an anaesthetized dog: at 10 to 15 mg/kg, intravenous amiodarone suppressed polymorphic ventricular systoles provoked by the intravenous injection of barium chloride in anaesthetized rabbits (n = 2) and dogs (n = 2). At 10 mg/kg, intravenous amiodarone suppressed ventricular extrasystoles induced by ligature of the anterior descending coronary artery in an anaesthetized dog. At 10 to 20 mg/kg, intravenous amiodarone suppressed atrial fibrillation induced by acetylcholine in anaesthetized dogs (n = 2).

At 10 mg/kg, intravenous amiodarone suppressed the ventricular tachycardia, induced by aconitine in an anaesthetized dog and the ventricular tachycardia induced by strophantine in morphinized dogs (n = 16).

In the isolated hearts of rats pretreated intravenously with single doses (21 to 42 μmol/kg: 3.5 to 7.5 mg), amiodarone prevented (in a dose-related fashion) both ventricular tachycardia, and ventricular fibrillation during regional myocardial ischemia and during reperfusion of ischemic muscle.

In anaesthetized guinea pigs (n = 10/group) amiodarone administered intravenously at single doses of 25 and 50 mg/kg statistically significantly protected against ouabain-induced ventricular flutter-fibrillation although it did not provide significant protection against cardiac arrest.

Microbiology

Amiodarone Hydrochloride for Injection is a sterile solution of amiodarone hydrochloride for intravenous administration.

The product is sterilized by aseptic filtration and is tested for sterility and bacterial endotoxins.

Toxicology

Acute Toxicity

Amiodarone hydrochloride was evaluated in acute oral studies in mice, rats, and dogs, and in acute intravenous studies in rats and dogs. Multiple-dose toxicity studies were performed by oral administration to mice (20 months), rats (3 to 104 weeks), dogs (4 weeks to 9 months), and pigs (3 or 10 months). Amiodarone was administered intravenously in multiple-dose toxicity studies to rabbits (6 weeks), dogs (4 weeks), and baboons (4 weeks).

Table 2 - ORAL AMIODARONE: ACUTE TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Mouse/NMRI Oral (gavage) 500 to 3000/Single dose The oral LD50 was greater than 3000 mg/kg. For technical reasons (high viscosity of the solutions at concentrations greater than 10%), the highest dose that could be administered was 3000 mg/kg.
Rat/Wistar Oral (gavage) 500, 750, 1000, 2000, 3000/Single dose The oral LD50 was greater than 3000 mg/kg. No deaths occurred at the highest dosage.
Dog* Oral (diet) 0, 1000, 3000, or 5000 in feed The oral LD50 was greater than 5000 mg/kg. No deaths occurred. All dogs vomited within 6 hours of ingestion. One dog given 5000 mg/kg demonstrated tremors 24 hours after ingesting the drug. This lasted for more than 96 hours and was accompanied by hindquarter paralysis.

* Report does not identify strain

Table 3 - INTRAVENOUS AMIODARONE HYDROCHLORIDE: ACUTE TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Rat/Wistar intravenous 100, 150, 200/single dose The IV LD50 was 135 mg/kg. Dyspnea, resulting in cyanosis, was observed premortem.
Rat/Wistar intravenous 100, 120, 140, 160, 180, 200/single dose The IV LD50 was 150 mg/kg.
Rat/SD(BR) intravenous Males 0, 100, 120, 150, 60, 180 Females 0, 160, 170, 180, 220/single dose The IV LD50 for males and females was 170 and 175 mg/kg, respectively. Clonic convulsions were observed as dosages of 120 mg/kg and above.
Dog/Beagle intravenous 5 minute injections of 25 - 150 5 minute injections of 75 - 100 20 minute injection of 100 -150/single dose The IV LD50 for a 5-minute infusion was 75 to 100 mg/kg. The IV LD50 for a 20-minute infusion was 150 mg/kg. Injections were followed by excitation with redness of the skin and mucus membranes, sedation, dyspnea, convulsions, and electrocardiographic alterations.
Dog* intravenous 0.75 mg/kg/min to 110 or 95 mg/kg 0.62 mg/kg/min to 124 mg/kg 0.45 mg/kg/min to 190 mg/kg/single dose The IV LD50 was 110 to 125 mg/kg for an infusion rate of 0.6 to 0.75 mg/kg per minute and was > 90 mg/kg for an infusion rate of 0.45 mg/kg per minute.

* Report does not identify sex or strain of dogs.

Table 4 - ORAL AMIODARONE: CHRONIC TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Rat/Wistar Oral (gavage) 100, 200, 300, 450, or 600/3 weeks* The LD50 was 420 mg/kg.
Rat/Wistar Oral (gavage) 0, 100, 200, 300, 450, or 600/for weeks* The LD50 was greater than 600 mg/kg. A dose related decrease in mean body weight of both males and females occurred.
Rat/Crl Br Oral (gavage) 10, 19 37.5, 75, or 150/ 4 weeks Drug treatment at 37.5 mg/kg or less did not produce any adverse reactions. At doses of 75 or 150 mg/kg, there was a deterioration in the animals’ health. Increased mortality occurred at 150 mg/kg.

Postmortem examination showed that those animals that died on test were cachectic. Body weight gains decreased in both sexes at 150 mg/kg and in females at 75 mg/kg; food intake was also reduced. Although there were no clinically significant changes in blood pressure among treated animals, heart rate changes did occur at dosages of 37.5 mg/kg and above. Significant increases in the number of neutrophils and a decrease in the number of lymphocytes were observed in the high-dose treatment group. Clinical chemistry values of BUN, alkaline phosphatase, and total and esterified cholesterol (dose related in males) were elevated at 75 mg/kg and above. There was an increase in T4 and a decrease in the T3/T4 ratio at the 75 mg/kg and 150 mg/kg.

At 75 and 150 mg/kg, there was an increase in lung and adrenal weights, and a decrease in thymus, prostate, seminal vesicle, uterine and ovarian weights. At 37.5 mg/kg and higher, the relative weight of the liver in females appeared slightly increased. Macroscopically, the only observation associated with the drug was a yellow colouring of mesenteric lymph nodes in most animals treated at 75 and 150 mg/kg. Historically, this proved to be a dose-dependent accumulation of foamy macrophages involving the mesenteric lymph nodes with spreading to the liver, spleen and lungs. The adrenal cortex contained lipid-like material. There was a moderate degree of thymic involution observed in high-dose animals and this was possibly associated with stress at this level.

The thyroids of treated animals presented a histologic appearance of increased activity.
Rat/Fisher 344 Oral (gavage) Vehicle-control, 160/7 days* Treated animals showed signs of toxicity by the fourth day of dosing. This included weakness accompanied by piloerection, epistaxis and softening of the feces. Reversibility of these symptoms did not occur until 8 days after the treatment had stopped and often persisted to the 20th day. One death was recorded on day 7 of administration. Initially, body weight gains were depressed in all groups but returned to normal by the end of the treatment schedule.

Increases in the weights of the liver and adrenals were also observed, but these too returned to control values 1 to 2 weeks after dosing had stopped. A marked decrease in thymus weight was partially reversible after 2 weeks and completely reversible after 8 weeks. Macroscopic examination revealed a white colouration of the mesenteric lymph nodes in animals sacrificed on days 7 and 14. Histologically, foam cells were present in the mesenteric lymph nodes and lungs. These changes disappeared after a recovery period of about 2 weeks.
Rat/Wistar Oral (gavage) Vehicle control, 100, 200, or 300/3months** Dose-related increases in mortality were observed (0 at 100 mg/kg, 15% at 200 mg/kg and 25% at 300 mg/kg). Body weights of male rats receiving 200 or 300 mg/kg were depressed 19% and 30%, respectively. Female body weights at 300 mg/kg were depressed by 14% relative to controls.

Hemoglobin values slightly depressed at 200 mg/kg and markedly decreased at 300 mg/kg. At 300 mg/kg the ratio of circulating lymphocytes to polymorphonuclear leukocytes increased during the study; this was more marked in females. Blood urea nitrogen (BUN) was significantly increased in both the 200 and 300 mg/kg groups. Blood glucose levels were not affected by the administration of the drug.

At 100 mg/kg, no microscopic lesions were noted except for some hypertrophy of the thyroid gland. With both the 200 and 300 mg/kg, there was centrilobular congestion in the liver which was more marked at high dose level. In 2 of 14 rats given 300 mg/kg, lesions of the myocardium were present.
Dog/Beagle Oral (capsule) Vehicle-control or 100/4 weeks A 38% decrease in mean body weight was observed in treated animals and this was associated with decreased food intake. One treated animal was moribund sacrificed due to its cachectic state. Autopsy revealed an abnormal increase in bile contained in the gall bladder and intestine. There were no other deaths during the study.

Clinically significant increases in SGPT (129%), SGOT (300%), and LDH (363%) were noted in treated animals. All other parameters were similar between dosed and control groups. Increases in absolute and relative weights of the adrenals and the liver plus the absence of a recognizable thymus were noted in the treated dogs.

Macroscopic examinations revealed congestion of the digestive mucosa (primarily in the small intestine), and the presence of an abnormal amount of bile in the gall bladder and/or the intestines in the treated animals.

Microscopic examination showed the presence of foamy cells in the mesenteric lymph nodes, spleen and lymphoid tissue of the digestive tract. The foamy cells were characterized by an abundance of polymorphic cytoplasmic inclusions of probable dyslipidic origin. Electron microscopy revealed the dyslipidosis to be widespread although minimal in any one tissue.
Dog/Beagle Oral (diet at 0 and 30 mg/kg, capsule at 150 mg/kg) Dietary control, 30 or 150/3 months** There were no deaths. At 150 mg/kg, gastrointestinal intolerance (vomiting, diarrhea and anorexia) was observed for the first 1 ½ months and intermittently thereafter. Excessive salivation was noted throughout. Concurrent with the epigastric distress, dogs receiving 150 mg/kg showed a 20% loss in weight during the first 40 days of dosing. Thereafter weight gains were normal.

Apart from minor changes in several hematology values, parameters were similar between control and treated groups. A dose-related increase in leukocyte counts was noted at all 3 sampling intervals and decreases on neutrophils during the last month in the high-dose group.

Clinical chemistry values were also similar between control and treated animals. SGPT levels rose in animals receiving 150 mg/kg/day during the first month of testing but were normal thereafter. Alkaline phosphatase levels in the high-dose group rose during the study but remained within the normal range for this species.

The results of the postmortem macroscopic examination were unremarkable. One dog in the high-dose group exhibited hypertrophy of the thyroid but histopathology was unremarkable. No generalized histopathology abnormalities were found which were related to the drug administration. All findings were slight and occurred either in or were isolated instances or were present in both treated and control animals and could not be attributed to the drug.
Dog*** Oral (diet) Dietary control, 30 or 60/9months One control animal died during the first month of the study and was replaced. There were no abnormal clinical observations or evidence of gastric intolerance in animals receiving amiodarone. Body weights and food intake were unaffected. The only significant laboratory abnormality was a dose-dependent hypercholesteremia.

Macroscopic and histological examinations revealed only incidental lesions probably secondary to incurment diseases. Organ weights were not markedly different between treated and control animals.
Pig** Oral (diet) Dietary control, 10, 20, 50 or 150/3 months At 150 mg/kg, clinical signs of toxicity include ataxia, hypotonia and no weight gain; appetite was not affected. At 1½ months, 2 high-dose animals died during blood collecting. An autopsy revealed only gastritis and gastric ulceration. At 2½ months, the remaining 2 high-dose pigs were sacrificed in extremis. Autopsy findings were unremarkable. No other mortalities were recorded. Animals in the other treated groups showed no signs of toxicity and weight gains parallelled those of the controls.

High-dose animals did not undergo blood tests due to the deaths of 2 animals at the first blood sampling and due to the poor health of the remaining 2 animals. In all other animals, results were within normal limits. Both the treated and control values for a number of the clinical tests were similar between groups.

Apart from the gastritis and ulcers noted in animals given 150 mg/kg, no other macroscopic lesions were attributed to drug intake. One control animal also displayed gastritis. Histologically, doses of 10, 20, or 50 mg/kg produced no toxic effects on any organs examined. At the 150 mg/kg dose, there were liver lesions and endocrine (pituitary, thyroid, adrenal) dysfunction in pigs treated for 2½ months. In the liver, this was characterized by a disorganization of the hepatic parenchyma, focal necrosis, sclerosed Kiernan's spaces, and brown pigmented macrophages in the intestinal spaces.

In the endocrine system, the adrenal cortex showed clusters of lymphomonocytes and hemorrhagic foci principally in the zona fasciculate. In both the zona glomerulosa and zona fasciculata of the adrenal cortex, there was evidence of hyperfunction. In the thyroid, numerous follicle cells that were larger than normal with vacuolar cytoplasm were suggestive of increased activity. In the pituitary of 1 pig in the 150 mg/kg, the basophilic cells were more numerous and larger than normal.
Pig** Oral (diet) Dietary control, 50/10 months There were no deaths, abnormal behaviour, or clinical signs of toxicity. Increase in body weight was parallel for treated and control animals. No abnormalities were noted for hematology, clinical chemistry, ophthalmic, or macroscopic examination.

* Treatment was followed by a sequential sacrifice of 7 animals on day 11, 18, 25, 36, 67, and 121 of study.
** Animals were dosed 5 days/week
*** Report does not identify strain

Table 5 - ORAL AMIODARONE: CHRONIC TOXICITY/CARCINOGENICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Mouse/BGC3F1 Oral (gavage) 0, 5, 16, 50/20 months No drug-related effects on mortality occurred. Adverse clinical observations mainly consisted of urogenital trauma, resulting from fighting between male cage mates, and palpable masses. The palpable masses were primarily related to the presence of neoplasms. Weight gain and food intake were slightly increased in treated males during the first months of the study only; the effect was not dose related.

A dose-related increase in the thyroid weight in both sexes was observed. Macroscopically, thyroid hypertrophy was observed. Histopathologically, a dose-related increase in incidence and degree of hyperplasia was seen in the thyroids of animals from test groups. However, the only tumors of the thyroid were diagnosed as follicular adenomas. These occurred in 1 control animal and in 4 high-dose animals and were within the normal range for this species at this age. No other non-neoplastic or neoplastic change associated with treatment was observed. The remainder of tumors diagnosed were recognized as those that occur commonly in mice. There was no increase in incidence or change in biological type of these tumors in treated animals when compared to controls. In addition, examination of blood smears taken at autopsy showed no treatment-related effect.
Rat/Sprague-Dawley CD Oral (gavage) 0, 5, 16, 50/104 weeks No effect on mortality occurred. Drug treatment at 16 and 50 mg/kg per day to males and females induced minor effects including salivation immediately after dosing, staining of the fur/reduced grooming, paddling of the forefeet, reduced food consumption, reduced body weight gain, decreased erythroid values, and increased alkaline phosphatase activity and cholesterol levels. Liver weight was marginally increased in males treated at 50 mg/kg per day.

At terminal examination, an increased incidence of pale foci in the lungs of all treated male groups and females given 16 or 50 mg/kg per day, an increased incidence of thyroid enlargement in all treated male groups, increased incidence of liver masses in males given 50 mg/kg per day, and a slightly higher incidence of pancreatic masses in treated male groups were observed. Liver weight was marginally higher in males given 50 mg/kg per day, and thyroid weight was markedly higher in males given 50 mg/kg per day.

An increased incidence of neoplastic changes to the thyroid (follicular tumors) occurred in all treated groups. These changes were statistically significant overall for all male groups, but only at 16 mg/kg per day and above in the females. Non-neoplastic findings included changes to the thyroid at all dosages, and lung lesions in all treated male groups and in females given 16 or 50 mg/kg per day. Lymph node changes occurred in males and females given 16 or 50 mg/kg/day, and systemic and thymic lesions occurred in males given 50 mg/kg per day.
Table 6 - ORAL AMIODARONE: CHRONIC TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Dog/Beagle Oral (gavage) 0, 12.5, 25, 50, 100 mg/kg/12 months plus a 3 month recovery period Mortality and adverse clinical signs (equilibrium and locomotion disorders, vomiting, diarrhea, tremors) occurred at 25 mg/kg per day and above.

Electrocardiograms were altered at 50 and 100 mg/kg per day. Dyslipidosis, characterized by the presence of foam cells was observed at 25 mg/kg per day and above in the lymph nodes and lungs. In the lung, these lesions appeared to be totally reversible after 3 months without treatment at 25 mg/kg per day. The dyslipidosis could be related to the increases in total and esterified cholesterol (without any modification of the ratio), together with a moderate but inconsistent increase in triglycerides and phospholipids. A malabsorption syndrome occurred in some animals treated at 100 mg/kg per day. This syndrome was characterized by diarrhea, vomiting, anorexia, weight loss, and partial or subtotal jejunal villi atrophy accompanied by the presence of foam cells observed histologically.

Changes in thyroid function were characterized by an increase in T4 at dose levels of 12.5 mg/kg per day and above, without any variation in T3 levels or the thyroid weight. There were no pathological changes in this organ attributed to drug treatment. The increase in T4 was reversible by the end of the recovery phase. Minor adverse effects such as cholestasis and nonspecific changes such as regression or disappearance of the thymus, amyotrophy, and altered spermatogenesis in males were also recorded at dosage levels of 50 and 100 mg/kg per day.

Reproductive Toxicity

Reproductive toxicology studies were performed by both oral and intravenous administration. Amiodarone was administered by oral gavage to mice, rats, and rabbits and intravenously to rats (continuous infusion) and rabbits (bolus injection). In addition, the mutagenic potential was assessed in studies supporting the oral formulation.

Table 7 - ORAL AMIODARONE: REPRODUCTIVE STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Mouse/NMRI Oral (gavage) 0 (water control), 5, 50, or 100/Gestation days 1 to 15 Drug treatment did not result in any fetal malformations in the mouse. However, there was a clear drug-related reduction in litter size due to an increase in the number of resorptions. It was concluded from this study that amiodarone was embryotoxic to mice. Since signs of maternal toxicity were not recorded in this study, no statement can be made about an association between maternal and fetal toxicity.
Mouse/Charles River Oral (gavage) 0 (vehicle control), 5, 50, or 100/ Gestation days 1 to 16;
50 mg/kg in an additional group/ Gestation days 6 to 16
Drug treatment (50 mg/kg) administered from days 6 to 16 gestation did not appear to be toxic to the fetus. In doses of 5, 50 and 100 mg/kg administered from days 1 to 16 gestation, the drug did not reduce the number of implantations or cause fetal malformation. The study demonstrated no teratogenicity in mice.
Rat/OFA (Sprague-Dawley) Oral (gavage) Vehicle control, 10, 30, 60, or 90/Males-64 days prior to mating and throughout the mating period.
Females - 64 days prior to mating, throughout the mating period, gestation, and until termination on day 21 postpartum.
There were no effects on F0 survival, clinical observation, or postpartum observations. Body weight gain of females given 60 mg/kg was slightly decreased beginning at week 8, and that of females given 90 mg/kg was decreased throughout the mating and gestation periods. This depression may have resulted from the significantly reduced litter weights and sizes of these groups. Body weight gain of males was marginally reduced only at the highest dose. Food consumption was similar in all groups. There was no effect on estrous cyclicity and pre-coital interval. However, the fecundity index was significantly depressed in the 90 mg/kg group.

Drug treatment had no adverse effect on parturition, although one female in the 60 mg/kg group died suddenly after delivering 9 live fetuses. During the lactation period, the mean body weight gain of the females was significantly depressed in the highest dose group for the first 10 days; other groups gained weight normally.

There were no observed drug-related abnormalities among the offspring. Postnatal viability was reduced in the 90 mg/kg group. Growth and functional development of offspring were similar in all groups, except in the 90 mg/kg group where body weight gain of offspring was markedly depressed from day 1 to day 10 postpartum but not thereafter.

Terminal necropsy of adults and of offspring which were not selected for continuation of the study did not reveal any treatment-related abnormalities.

The functional development of the special senses (hearing and vision) and reflexes of the offspring was comparable in all treated and control groups as was the body weight gain from 40 days postpartum onwards and of estrus cycles from day 80 to day 100 postpartum.
Rat/Wistar Oral (gavage) Water control and 200 / Gestation day 1 to 21 Drug-treated females demonstrated adverse physical examination findings (listless, shaggy, and dull fur) and reduced weight gain. Conjunctivitis and a nasal suppuration mixed with blood were observed in several of the treated rats. Six of the 30 treated rats died during the study. These animals were observed to have macerations of the abdominal viscera and severe enteritis. Excluding deaths, the percentage of successful mating was comparable in the treated and control groups.

Drug treatment (200 mg/kg) was associated with embryotoxicity. The number of resorptions expressed as a percentage of pregnancies or as a percentage of implantations was significantly increased in the treated group as compared to controls. The percentage of females presenting fetuses with major deformities as well as the percentage of fetuses with major deformities was increased in the treated group. Given the limited number of viable litters from the treated rats, however, no conclusions regarding teratogenicity can be drawn. The mean weight of fetuses from the treated group was also slightly less than the control group.
Rat/Sprague-Dawley Oral (gavage) 0 (Water control), 10, 30, or 90 / 64 days premating, during mating and from gestation day 1 to 19 (females only) Prior to mating, treated animals showed no changes in behaviour, food consumption, or estrus cyclicity. Mean body weight gain was slightly depressed in females receiving 90 mg/kg. Although seven deaths occurred during the pre-mating period, none were considered related to amiodarone treatment.

The mating period tended to be shorter in the treated groups than controls, though not significantly shorter. There was a significant increase in the number of barren matings in the 90 mg/kg group.

The decrease in number of corpora lutea and implantation sites among dams of the highest dose treatment group may partially explain the reduced fertility rate. Because total litter loss due to resorption occurred in 1 or 2 of the dams from each treatment group and none occurred in the control group, the percentage of resorbed fetuses was higher in the treated groups than in the control group. Discounting these total litter losses, no significant increase in fetal resorptions occurred in any of the treated groups.

No teratogenicity was observed. The number of fetuses which presented minor abnormalities (most commonly incomplete skeletal ossification) was significantly greater in the treated groups compared to controls. However, these minor abnormalities resulted primarily from fetal growth retardation, which is a reversible phenomenon, and are not indicative of a true teratogenic event. Thus, it was concluded that amiodarone was without teratogenic potential in rats.
Rat/Sprague-Dawley Oral (gavage) 0 (vehicle control), 10, 30, or 90/ gestation day 14 to postpartum day 21 There were no clinical signs of toxicity and no rats died. A decrease in mean maternal weight gain was observed beginning on gestation day 16 in the 90 mg/kg treatment group. No differences in weight gain were seen during lactation. The duration of gestation was unchanged and parturition was unaffected by amiodarone treatment. The mean live litter size and sex ratio were comparable in treated and control groups. The mean fetal weights were significantly reduced (18% smaller than control) only at 90 mg/kg. This difference was increased on days 4 to 10 of neonatal life (-29% and -31%, respectively), but remained stable thereafter. Although the number of young born to treated females of this group was the same as in the control group, neonatal mortality was higher. Of those terminal offspring, one-third died between birth and day 4, and the remaining two-thirds died between day 5 and weaning.

Necropsy revealed no abnormalities related to drug intake in any of the offspring sacrificed on day 21. One offspring from the 10 mg/kg group exhibited agenesis of the right hind limb and a short tail.
Rat/Sprague-Dawley Oral (gavage) 0 (water control), 5, 50, or 100/gestation days 1 to 15 Drug treatment did not have any toxic effect on fetuses of rats at administered doses up to 100 mg/kg. The ratio of the number of living fetuses counted at term to the number of implantation sites was not significantly different in treated and untreated groups. None of the fetuses examined showed any external malformations, microscopic or skeletal abnormalities.
Rabbit/Belgian Hare Oral (gavage) 0 (water control), 5, 50, or 100/gestation days 1 to 18 Neither the number of implantations or live fetuses observed at sacrifice appeared to vary among treated and control groups. The number of resorptions was higher than control in the low- and mid-dose treatment groups, but was lower in the high-dose group. Drug treatment did not affect the fecundity of the animals. Examination of fetuses revealed no malformations.
Table 8 - INTRAVENOUS AMIODARONE: REPRODUCTIVE TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Rat/CD BR intravenous (infusion) 0 (saline), 0 (stock), 25, 50, 100/ gestation days 8-16 An increased incidence of minor adverse physical examination findings related to the injection procedures and necropsy observations correlated with increased dosage and treatment duration. Body weight gains were decreased in the control-stock group; a dose-related reduction in body weight gains occurred in animals in the 50 and 100 mg/kg dosage groups compared to the saline and/or control-stock group. Food consumption was decreased for animals in the 100 mg/kg dosage group compared to either control group.

Resorptions were increased, and live litter size and fetal body weights were decreased at a dosage of 100 mg/kg. Delayed ossification of the sternum and metacarpals occurred at a dosage of 100 mg/kg; this delay was reversible and was related to the reduced fetal body weights at this dosage level. Fetal thyroid tissues appeared normal in all groups.

Based on reduced body weight gains and food consumption at a dosage of 100 mg/kg, the maternal NTEL was 50 mg/kg. The developmental NTEL was 50 mg/kg based on resorptions, reductions in live litter size and fetal body weights, and delayed ossification of the sternum and metacarpals.
Rabbit/Dutch intravenous 0, 5, 10, and 25/ gestation days 8 - 16 No drug-related changes in behaviour or maternal body weight were observed during the study. The only evidence of maternal toxicity observed was an increase in mortality that was statistically significant at the high dose. The incidence of deaths was 1,3,5 and 8 in the control, low middle, and high dose groups, respectively. Necropsies revealed degeneration of the liver in the control, bronchopneumonia in the low-dose group, and bronchopneumonia with peritonitis and enteritis in the middle- and high-dose rabbits. Mean fetal weights were significantly decreased at the low- and middle-dose levels. Evidence of embryotoxicity was significant at 10 and 25 mg/kg. However, there was no significant difference in the number of minor abnormalities and no major abnormalities were observed.

Long Term Toxicity/Carcinogenicity

Table 9 - INTRAVENOUS AMIODARONE HYDROCHLORIDE: SUBCHRONIC TOXICITY STUDIES
Species/
Strain
Mode of
Administration
Dosage
(mg/kg per day)/
Duration
Results
Rabbit/Dutch intravenous 0, 5, 10, and 25/6 weeks No drug related mortality occurred. There was a statistically significant decrease in red blood cell count and hemoglobin values for both males and females at all dose levels. Significant increases in total cholesterol (143% to 200%) were observed at all dose levels. Total lipids were also significantly increased (168%) in males at 25 mg/kg. For females, total lipids were significantly increased at 5 (127%) and 10 (147%) mg/kg, but not at 25 mg/kg. All other blood chemistry parameters showed no difference between treated and control animals. At necropsy, several treated animals exhibited white patches and/or signs of cirrhosis in the liver. Microscopic evaluation revealed hepatocytes and Kupffer cells containing numerous pigments (probably hemosiderines) in several control and treated rabbits. In several treated animals (2, 2, and 1 rabbit at 5, 10, and 25 mg/kg, respectively), part of the hepatic parenchyma degenerated and was replaced by necrotic tissue surrounded by fibrous tissue, giving a cirrhotic appearance. However, these histologic changes were not considered related to drug administration. As a result of the hematological and biochemical changes, a no toxicologic effect level (NTEL) could not be determined.
Dog/Beagle intravenous 0, 7.5, 15, 30, and 60/4 weeks Mortality was observed at 60 mg/kg. Adverse physical examination findings were observed in all groups; however, only sedation occurred solely in drug treated groups at dosages of 30 mg/kg and above. Body weight and food consumption were decreased at 30 and 60 mg/kg. Hematologic (increased fibrinogen and monocyte levels; decreased red blood cell counts, hematocrit, and hemoglobin level), biochemical [increased cholesterol (122% to 216%), triglycerides, alanine aminotransferase, alkaline phosphatase, potassium, and T4; and decreased protein and T3/T4 ratio] changes occurred at all dosage levels, although most frequently at dosages of 30 mg/kg and above.

Alterations in cardiac parameters (decreased heart rate, lengthened PR and ST segments, increased T wave amplitude) occurred at 60 mg/kg. Liver weights were increased in all drug-treated groups while adrenal and prostate weights were decreased at 60 mg/kg. Macroscopic changes to the liver, bile, colonic mucosa, and renal cortex occurred in all drug-treated groups.

Many of the drug-treated dogs exhibited clots and outgrowths of the valvula tricuspidalis and pulmonary lesions (congestion, crepitation, foamy discharge at sectioning) were observed in the 3 animals that died during the study. Injection site lesions were observed in all groups, including controls. However, the severity in the drug-treated groups followed a dose-response pattern. Microscopic examination revealed foamy macrophages in the lymph nodes, spleen, and Peyer's patches at 60 mg/kg and in 1 dog that received 30 mg/kg. Dogs at all levels showed islets of clear cells in the adrenal cortex. Marked cholestasis and thymic regression were observed at 60 mg/kg; evidence of increased thyroid activity was observed in all treated animals. As a result of the observed effects, a NTEL could not be determined.
Baboon/Papio papio intravenous 0, 12.5, 25, and 50/4 weeks One 12.5 mg/kg female and all four 50 mg/kg animals died or were killed in extremis. A dosage of 50 mg/kg produced gradual changes in the general condition of the animals (prostration, piloerection) from week 2 onward. Decreased food consumption in all drug-treated groups was associated with body weight loss in the 25 and 50 mg/kg groups. Decreased heart rates (lengthening of the ST segment) were noted in the 25 and 50 mg/kg groups. Changes in hematologic (decreased red blood cell count, hemoglobin, hematocrit, mean cell hemoglobin, and mean cell hemoglobin concentration; increased reticulocytes, neutrophils, and monocytes) and biochemical (increased bilirubin, triglycerides, blood urea nitrogen, creatinine, and T4 levels) parameters were observed in all drug-treated groups; the majority of effects were observed at 25 and 50 mg/kg.

Organ weight changes included a thyroid weight increase at all dose levels. Increased liver and kidney weights occurred at the higher dosage levels and a dose-related thymus weight decrease occurred. Discoloured livers and a cirrhotic appearance was observed in all 4 baboons at 50 mg/kg. All 3 of the animals that died during the study exhibited cardiac lesions, 2 of which had a clot adherent to the endocardium and valvulae in the right side of the heart, while the third showed discolouration of the myocardium and necrotic magma in the muscle. These changes were probably attributed to the irritative properties of amiodarone hydrochloride when the compound is repeatedly administered into the cephalic or saphenous veins. Intravenous treatment with amiodarone HCl caused indurations, edema, abscesses, and local necrosis with eschars at the injection sites; the degree of these lesions was dose related. The vehicle alone induced only local indurations that partially regressed when the injection site was changed. Microscopic examination revealed a dose-related increase in incidence and degree of thymic regression at all dose levels, changes in the gall bladder at the higher doses, and colloid retention in the thyroids in all treated groups. As a result of the observed mortality, effects of the thyroid, and injection site lesions, a NTEL could not be determined.
Table 10 - MUTAGENICITY STUDIES
Study Test System Concentrations Conclusions
Ames Test S.typhimurium
Tester Strains
TA 98
TA 100
TA 1535
TA 1537
TA 1538
Not identified No evidence of mutagenicity occurred in the presence or absence of S-9.
Lysogenic Induction Test Bacterial Strains
GY5027
GY4015
Not identified At concentrations that approached toxic levels (~ 100 micrograms/dish), no increase in spontaneous lysis occurred.
Micro-nucleus Test Mouse/Charles River 50, 100, 225 mg/kg (each animal received 2 intraperitoneal injections administered over a 24 hour period) No increase in number of micronuclei per 200 polychromatic erythrocytes was induced by drug treatment.