Amerge: Indications, Dosage, Precautions, Adverse Effects
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Amerge - Product Information

Manufacture: GlaxoSmithKline
Country: United States
Condition: Migraine, Migraine Headache (Migraine)
Class: Antimigraine agents
Form: Tablets
Ingredients: croscarmellose sodium, hydroxypropyl methylcellulose, indigo carmine aluminium lake (FD&C Blue No. 2) [2.5 mg tablet only], iron oxide yellow [2.5 mg tablet only], lactose, magnesium stearate, microcrystalline cellulose, titanium dioxide, and triacetin

Summary Product Information

Route of Administration Dosage Form / Strength Nonmedicinal Ingredients
Oral Tablets/
1 mg and 2.5 mg
croscarmellose sodium, hydroxypropyl methylcellulose, indigo carmine aluminium lake (FD&C Blue No. 2) [2.5 mg tablet only], iron oxide yellow [2.5 mg tablet only], lactose, magnesium stearate, microcrystalline cellulose, titanium dioxide, and triacetin

Indications and Clinical Use

AMERGE (naratriptan as naratriptan hydrochloride) is indicated for the acute treatment of migraine attacks with or without aura in adults.

AMERGE is not intended for the prophylactic therapy of migraine or for use in the management of hemiplegic, basilar or ophthalmoplegic migraine (see CONTRAINDICATIONS). Safety and efficacy have not been established for cluster headache, which is present in an older, predominantly male population.

Geriatrics (> 65 Years of Age)

The safety and efficacy of AMERGE have not been adequately studied in individuals over 65 years of age. AMERGE is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in elderly patients who have reduced renal function. In addition, elderly patients are more likely to have decreased hepatic function; they are at higher risk for Coronary Artery Disease (CAD), and blood pressure increases may be more pronounced in the elderly. Clinical studies of AMERGE did not include patients over 65 years of age. Its use in this age group is, therefore, not recommended (see WARNINGS AND PRECAUTIONS).

Pediatrics (< 18 Years of Age)

Adolescents (12-17 Years of Age)

The efficacy of AMERGE at single doses of 0.25, 1.0 and 2.5 mg was not demonstrated to be greater than placebo in adolescents (12-17 years). Furthermore, the safety of AMERGE in adolescents has not been established. Therefore, the use of the drug in adolescents is not recommended (see WARNINGS AND PRECAUTIONS).

Children (< 12 Years of Age)

The safety and efficacy of AMERGE have not been studied in children under 12 years of age. Use of the drug in this age group is, therefore, not recommended (see WARNINGS AND PRECAUTIONS).

Contraindications

AMERGE is contraindicated in patients with history, symptoms, or signs of ischemic cardiac, cerebrovascular or peripheral vascular syndromes, valvular heart disease or cardiac arrhythmias (especially tachycardias). In addition, patients with other significant underlying cardiovascular diseases (eg. atherosclerotic disease, congenital heart disease) should not receive AMERGE. Ischemic cardiac syndromes include, but are not limited to, angina pectoris of any type (e.g., stable angina of effort and vasospastic forms of angina such as the Prinzmetal’s variant), all forms of myocardial infarction, and silent myocardial ischemia. Cerebrovascular syndromes include, but are not limited to, strokes of any type as well as transient ischemic attacks (TIAs). Peripheral vascular disease includes, but is not limited to, ischemic bowel disease, or Raynaud’s syndrome (see WARNINGS AND PRECAUTIONS).

Because AMERGE can give rise to increases in blood pressure, it is contraindicated in patients with uncontrolled or severe hypertension (see WARNINGS AND PRECAUTIONS).

Ergot-containing drugs have been reported to cause prolonged vasospastic reactions. Because AMERGE may also cause coronary vasospasm and these effects may be additive, the use of AMERGE within 24 hours before or after treatment with other 5HT1 receptor agonists, or ergotamine-containing drugs or their derivatives (eg. dihydroergotamine, methysergide) is contraindicated.

AMERGE is contraindicated in patients with hemiplegic, basilar, or ophthalmoplegic migraine.

AMERGE is contraindicated in patients with severe renal impairment (creatinine clearance <15 mL/min) (see DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY).

AMERGE is contraindicated in patients with severe hepatic impairment (Child-Pugh grade C) (see DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY).

AMERGE is contraindicated in patients with hypersensitivity to naratriptan or to any component of the formulation, or component of the container. For a complete listing, see the DOSAGE FORMS, COMPOSITION AND PACKAGING section of the Product Monograph.

Warnings and Precautions

General

AMERGE should only be used where a clear diagnosis of migraine has been established.

Cardiovascular

Risk of Myocardial Ischemia and/or Infarction and Other Adverse Cardiac Events:

AMERGE has been associated with transient chest and/or neck pain and tightness, which may resemble angina pectoris. In rare cases, the symptoms have been identified as being the likely result of coronary vasospasm or myocardial ischemia. Rare cases of serious coronary events or arrhythmia have occurred following use of another 5HT1-agonist. AMERGE should not be given to patients who have documented ischemic or vasospastic coronary artery disease (see CONTRAINDICATIONS). It is strongly recommended that AMERGE not be given to patients in whom unrecognised coronary artery disease (CAD) is predicted by the presence of risk factors (e.g. hypertension, hypercholesterolemia, smoking, obesity, diabetes, strong family history of CAD, female who is surgically or physiologically postmenopausal, or male who is over 40 years of age) unless a cardiovascular evaluation provides satisfactory clinical evidence that the patient is reasonably free of coronary artery and ischemic myocardial disease or other significant underlying cardiovascular disease. The sensitivity of cardiac diagnostic procedures to detect cardiovascular disease or predisposition to coronary artery vasospasm is unknown. If, during the cardiovascular evaluation, the patient’s medical history or electrocardiographic investigations reveal findings indicative of or consistent with coronary artery vasospasm or myocardial ischemia, AMERGE should not be administered (see CONTRAINDICATIONS).

For patients with risk factors predicative of CAD who are considered to have a satisfactory cardiovascular evaluation, the first dose of AMERGE should be administered in the setting of a physician’s office or similarly medically staffed and equipped facility. Because cardiac ischemia can occur in the absence of clinical symptoms, consideration should be given to obtaining electrocardiograms (ECG) in patients with risk factors during the interval immediately following AMERGE administration on the first occasion of use. However, an absence of drug-induced cardiovascular effects on the initial dose does not preclude the possibility of such effects occurring with subsequent administrations.

Intermittent long-term users of AMERGE who have or acquire risk factors predictive of CAD, as described above, should receive periodic interval cardiovascular evaluations over the course of treatment. If symptoms consistent with angina occur after the use of AMERGE, ECG evaluation should be carried out to look for ischemic changes.

The systemic approach described above is intended to reduce the likelihood that patients with unrecognized cardiovascular disease will be inadvertently exposed to AMERGE.

Discomfort in the chest, neck, throat and jaw (including pain, pressure, heaviness, tightness, dyspnea) has been reported after administration of AMERGE. Because 5-HT1 agonists may cause coronary artery vasospasm, patients who experience signs or symptoms suggestive of angina following AMERGE should be evaluated for the presence of CAD or a predisposition to variant angina before receiving additional doses, and should be monitored electrocardiographically if dosing is resumed and similar symptoms recur. Similarly, patients who experience other symptoms or signs suggestive of decreased arterial flow, such as ischemic bowel syndrome or Raynaud’s syndrome following naratriptan administration should be evaluated for artherosclerosis or predisposition to vasospasm (see CONTRAINDICATIONS and ADVERSE DRUG REACTIONS, Clinical Trial Adverse Drug Reactions).

Cardiac Events and Fatalities Associated with 5-HT1 Agonists

AMERGE can cause coronary artery vasospasm. Serious adverse cardiac events, including acute myocardial infarction, life threatening disturbances of cardiac rhythm and death have been reported within a few hours following the administration of 5-HT1 agonists. Considering the extent of use of 5-HT1 agonists in patients with migraine, the incidence of these events is extremely low.

Premarketing Experience with AMERGE

Among approximately 3500 patients with migraine who participated in premarketing clinical trials of AMERGE, four patients treated with single oral doses of AMERGE ranging from 1 to 10 mg experienced asymptomatic ischemic ECG changes with at least one, who took 7.5 mg, likely due to coronary vasospasm.

Cerebrovascular Events and Fatalities with 5-HT1 Agonists

Cerebral hemorrhage, subarachnoid hemorrhage, stroke and other cerebrovascular events have been reported in patients treated with 5-HT1 agonists, and some have resulted in fatalities. In a number of cases, it appears possible that the cerebrovascular events were primary, the agonist having been administered in the incorrect belief that the symptoms experienced with a consequence of migraine, when they were not. Before treating migraine headaches with AMERGE in patients not previously diagnosed as migraineurs, and in migraineurs who present with atypical symptoms, care should be taken to exclude other potentially serious neurological conditions. If a patient does not respond to first dose, the opportunity should be taken to review the diagnosis before a second dose is given. It should be noted that patients with migraine may be at increased risk of certain cerebrovascular events (e.g. stroke, hemorrhage, TIA).

Special Cardiovascular Pharmacology Studies

In subjects (n=10) with suspected coronary artery disease undergoing angiography, naratriptan at a subcutaneous dose of 1.5 mg produced an 8% increase in aortic blood pressure, an 18% increase in pulmonary artery blood pressure, and an 8% increase in systemic vascular resistance. In addition, mild chest pain or tightness was reported by four subjects. Clinically significant increases in blood pressure were experienced by three of the subjects (two of whom also had chest pain/discomfort). Diagnostic angiogram results revealed that 9 subjects had normal coronary arteries, and 1 had insignificant coronary artery disease.

Migraine patients (n=35) free of cardiovascular disease were subjected to assessments of myocardial perfusion by positron emission tomography while receiving subcutaneous naratriptan 1.5 mg in the absence of a migraine attack. Naratriptan was associated with a reduced coronary vasodilatory reserve (∼10%), increased coronary resistance (∼20%), and decreased hyperemic myocardial blood flow (∼10%). The relevance of these findings to the use of recommended oral doses of naratriptan is not known.

Other Vasospasm-Related Events

5-HT1 agonists may cause vasospastic reactions other than coronary artery vasospasm. Extensive post-market experience has shown the use of naratriptan to be associated very rare occurrences of peripheral vascular ischemia and colonic ischemia with abdominal pain and bloody diarrhea.

Increases in Blood Pressure

Elevations in blood pressure have been reported following use of AMERGE. At the recommended oral doses, the elevations are generally small (population average maximum increases of < 5 mmHg systolic and < 3 mmHg diastolic at the 2.5 mg dose.) The effects may be more pronounced in the elderly and hypertensive patients. In a pharmacodynamic study conducted in normotensive patients (n=12) and in hypertensive patients controlled by antihypertensive treatment (n=12), the pressor effects of AMERGE were greater in hypertensive patients (weighted mean increases in systolic and diastolic blood pressure of 6 and 4 mmHg in hypertensive subjects versus 3 and 2 mmHg in normotensive patients receiving two 2.5 mg doses separated by a 2 hour time interval). Two hypertensive patients experienced three events of chest discomfort while receiving naratriptan. Significant elevation in blood pressure, including hypertensive crisis, has been reported on rare occasions in patients receiving 5-HT1 agonists with and without a history of hypertension. AMERGE is contraindicated in patients with uncontrolled or severe hypertension (see CONTRAINDICATIONS).

In patients with controlled hypertension, AMERGE should be administered with caution, as transient increases in blood pressure and peripheral vascular resistance have been observed in a small portion of patients.

Immune

Hypersensitivity

Rare hypersensitivity (anaphylaxis/anaphylatoid) reactions may occur in patients receiving 5-HT1 agonists, such as AMERGE. Such reactions can be life threatening or fatal. In general, hypersensitivity reactions to drugs are more likely to occur in individuals with a history of sensitivity to multiple allergens (see CONTRAINDICATIONS). Owing to the possibility of cross-reactive hypersensitivity reactions, AMERGE should not be used in patients having a history of hypersensitivity to sumatriptan or chemically-related 5-HT1 receptor agonists. As AMERGE contains a sulphonamide component, there is a theoretical risk of hypersensitivity reactions in patients with known hypersensitivity to sulphonamides.

Neurologic

Care should be taken to exclude other potentially serious neurologic conditions before treating headache in patients not previously diagnosed with migraine or who experience a headache that is atypical for them. There have been rare reports where patients received 5-HT1 agonists for severe headaches that were subsequently shown to have been secondary to an evolving neurologic lesion. For newly diagnosed patients or patients presenting with atypical symptoms, the diagnosis of migraine should be reconsidered if no response is seen after the first dose of AMERGE.

Seizures

Caution should be observed if AMERGE is to be used in patients with a history of epilepsy or structural brain lesions, which lower the convulsion threshold.

Selective Serotonin Reuptake Inhibitors/Serotonin Norepinephrine Reuptake Inhibitors and Serotonin Syndrome

Cases of life-threatening serotonin syndrome have been reported during combined use of selective serotonin reuptake inhibitors (SSRIs)/serotonin norepinephrine reuptake inhibitors (SNRIs) and triptans. If concomitant treatment with AMERGE and SSRIs (e.g. fluoxetine, paroxetine, sertraline) or SNRIs (e.g. venlafaxine) is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases. Serotonin syndrome symptoms may include mental status changes (e.g. agitation, hallucinations, coma), autonomic instability (e.g. tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g. hyperreflexia, incoordination) and/or gastrointestinal symptoms (e.g. nausea, vomiting, diarrhea) (see DRUG INTERACTIONS, SSRIs/SNRIs).

Psychomotor Impairment

In a study of psychomotor function in healthy volunteers, single oral 5 and 10 mg doses of AMERGE were associated with sedation and decreased alertness. Although these doses are higher than those recommended for the treatment of migraine, patients should be cautioned that drowsiness may occur following treatment with AMERGE. They should be advised not to perform skilled tasks (e.g. driving or operating machinery) if drowsiness occurs.

Ophthalmologic

Melanin Binding

In pigmented rats treated with a single oral dose (10 mg/kg) of radiolabelled naratriptan, radioactivity was detected in the eyes at 3 months post-administration, a finding which suggests that the drug or its metabolites may bind to the melanin of the eye. The possible clinical significance of this finding is unknown. No systematic monitoring of ophthalmologic function was undertaken in clinical trials. Prescribers should consider the possibility of long-term ophthalmologic effects due to accumulation of naratriptan in melanin-rich tissues.

Medication Overuse Headache

Overuse of acute migraine treatments has been associated with the exacerbation of headache (medication overuse headache, MOH) in susceptible patients. Withdrawal of the treatment may be necessary.

Special Populations

Pregnant Women

The safety of AMERGE for use during human pregnancy has not been established. AMERGE can cross the placenta in pregnant rats and rabbits, but it is not known if AMERGE can cross the human placental barrier. AMERGE should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing Women

AMERGE and/or its metabolites are distributed into the milk of lactating rats (at 2 hours post oral gavage dosing, levels in milk were 3.5 times higher than maternal plasma levels). It is not known if AMERGE is secreted into the human breast milk. Therefore, caution should be exercised when considering the administration of AMERGE to nursing women.

Children (< 12 Years of Age)

Safety and efficacy of AMERGE have not been studied in children under 12 years of age. Use of the drug in this age group is, therefore, not recommended.

Adolescents (12-17 Years of Age)

The efficacy of AMERGE at single doses of 0.25, 1.0 and 2.5 mg was not demonstrated to be greater than placebo in adolescents (12-17 years). Furthermore, the safety of AMERGE in adolescents has not been established. Therefore, the use of the drug in adolescents is not recommended.

Geriatrics (> 65 Years of Age)

The safety and effectiveness of AMERGE have not been adequately studied in individuals over 65 years of age. AMERGE is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in elderly patients who have reduced renal function. In addition, elderly patients are more likely to have decreased hepatic function; they are at higher risk for CAD, and blood pressure increases may be more pronounced in the elderly. Clinical studies of AMERGE did not include patients over 65 years of age. Its use in this age group is, therefore, not recommended.

Hepatic Impairmen

AMERGE should be administered with caution to patients with impaired hepatic function (see CONTRAINDICATIONS, DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY.)

Renal Impariment

AMERGE should be administered with caution to patients with impaired renal function (see CONTRAINDICATIONS, DOSAGE AND ADMINISTRATION and ACTION AND CLINICAL PHARMACOLOGY.)

Monitoring and Laboratory Tests

No specific laboratory tests are recommended for monitoring patients prior to and/or after treatment with AMERGE.

Dependence/Tolerance

Dependence Liability

In one clinical study enrolling 12 subjects, all of whom had experience using oral opiates and other psychoactive drugs, subjective responses typically associated with many drugs of abuse were produced with less intensity during treatment with AMERGE (1 to 5 mg) than with codeine (30 to 90 mg). Long term studies (12 months) in migraine patients using AMERGE revealed no evidence of increased drug utilization.

Adverse Reactions

Serious cardiac events, including some that have been fatal, have occurred following the use of 5-HT1 agonists. These events are extremely rare and most have been reported in patients with risk factors predictive of CAD. Events reported have included coronary artery vasospasm, transient myocardial ischemia, myocardial infarction, ventricular tachycardia and ventricular fibrillation (see CONTRAINDICATIONS and WARNINGS AND PRECAUTIONS).

Clinical Trial Adverse Drug Reactions

Because clinical trials are conducted under very specific conditions the adverse reaction rates observed in the clinical trials may not reflect the rates observed in practice and should not be compared to the rates in the clinical trials of another drug. Adverse drug reaction information from clinical trials is useful for identifying drug-related adverse events and for approximating rates.

Experience in Clinical Trials with AMERGE

Typical 5-HT1 Agonist Adverse Reactions

As with other 5-HT1 agonists, AMERGE has been associated with sensations of heaviness, pressure, tightness or pain which may be intense. These may occur in any part of the body including the chest, throat, neck, jaw and upper limb.

Acute Safety

The safety and efficacy of the 1 and 2.5 mg doses of AMERGE were investigated in four placebo-controlled clinical trials in adult migraine patients. Two of these trials were of parallel group design and involved the treatment of a single migraine attack. A third study was of crossover design and involved the treatment of one migraine attack per dose group. The fourth study was a parallel group trial in which patients treated up to 3 migraine attacks. In all studies, patients who achieved headache relief at 240 minutes post-dose, but experienced a worsening of severity between 4 and 24 hours post-dosing, were permitted to take a second dose of double-blind medication identical to the first.

The overall incidence of adverse events following doses of 1 mg or 2.5 mg AMERGE (one or more doses) was similar to placebo (28.5% and 30.2% versus 28.9% with placebo). AMERGE was generally tolerated, and most adverse reactions were mild, transient and self-limiting. The most common adverse events to occur at higher rate than in the corresponding placebo group were malaise/fatigue (2.4% versus 0.8% with placebo) and neck/throat/jaw sensations (2.1% versus 0.3% with placebo). Table 1 lists the most common adverse events that occurred in the four large placebo-controlled clinical trials. Only events that occurred at a frequency of 1% or more in the AMERGE 2.5 mg or 1 mg group and were more frequent in that group than in the placebo group are included in Table 1. From this table, it appears that many of these adverse events are related.

Table 1 Treatment-Emergent Adverse Events in Placebo-Controlled Clinical Trials Reported by at Least 1% of Patients with Migraine
Placebo AMERGE 1 mg AMERGE 2.5 mg
Symptoms of Potentially Cardiac Origin
Neck/throat/jaw sensations* 0.3% 1.7% 2.1%
Chest sensations* 1.1% 0.8% 1.2%
Upper limb sensations* 0.3% 0.5% 1.4%
Neurological
Dizziness 1.5% 1.0% 2.2%
Drowsiness/sleepiness 0.8% 0.9% 1.7%
Paresthesia 0.8% 1.6% 1.5%
Head/face sensations* 0.5% 0.5% 1.3%
Headache 0.2% 0.4% 1.0%
Gastrointestina
Nausea 6.2% 5.9% 6.3%
Hyposalivation 0.3% 0.5% 1.0%
Non-site specific
Malaise and fatigue 0.8% 1.6% 2.4%

*The term “sensations” encompasses adverse events described as pain and discomfort, pressure, heaviness, constriction, tightness, heat/burning sensation, paresthesia, numbness, tingling and strange sensations.

Long-Term Safety

In a long-term open study, 417 patients treated 15,301 migraine attacks with AMERGE over a period of up to 1 year. The most common adverse events in descending order of frequency were as follows: nausea (16%); malaise/fatigue (11%); drowsiness (10%); chest sensations* (8%); neck/throat/jaw sensations* (8%); parathesia (7%); head/face sensations* (6%); vomiting (6%); and dizziness (5%). Due to the lack of a placebo arm in this study, the role of AMERGE in causation cannot be reliably determined (*see footnote for Table 1).

Other Adverse Events Observed in Association with AMERGE

In the paragraphs that follow, the frequencies of less commonly reported adverse clinical events are presented. Because some events were observed in open and uncontrolled studies, the role of AMERGE in their causation cannot be reliably determined. All reported events are included except those already listed in Table 1, those too general to be informative, and those not reasonably associated with the use of the drug. Event frequencies are calculated as the number of patients reporting an event divided by the total number of patients (N=2790) exposed to AMERGE. Events are further classified within body system categories and enumerated in order of decreasing frequency using the following definitions: common adverse events are defined as those occurring in at least 1/100 patients; uncommon adverse events are those occurring in 1/100 to 1/1,000 patients; rare adverse events are those occurring in fewer than 1/1,000 patients.

General

Common: paresthesia and heat sensations; Uncommon: chills and/or fever, description of odor or taste and feelings of pressure/tightness/heaviness; Rare: allergies, allergic reactions, mobility disorders and faintness.

Cardiovascular

Uncommon: palpitations, increased blood pressure, tachyarrhythmias, abnormal ECGs and syncope; Rare: bradycardia, hypotension, varicosities and heart murmur.

Ear, Nose, and Throat

Common: ear, nose and throat infections; Uncommon: phonophobia, sinusitis and upper respiratory inflammation; Rare: allergic rhinitis, labyrinthitis, tinnitus, ear, nose and throat hemorrhage and difficulty hearing.

Endocrine and Metabolism

Uncommon: thirst, polydipsia, dehydration and fluid retention; Rare: hyperlipidemia, hypercholesterolemia, hypothyroidism, hyperglycemia, glycosuria, ketonuria and parathyroid neoplasm.

Gastrointestinal

Common: vomiting; Uncommon: dyspeptic syndromes, diarrhea, hyposalivation, gastrointestinal discomfort and pain, gastroenteritis and constipation; Rare: abnormal live function tests, abnormal bilirubin levels, salivary gland swelling, hemorrhoids, gastritis, esophagitis, oral itching and irritation, regurgitation, reflux and gastric ulcers.

Musculoskeletal

Uncommon: musculoskeletal/muscle pain, muscle cramps, muscle spasms, arthraligia and articular rheumatism; Rare: joint and muscle stiffness, tightness and rigidity.

Neurologic

Common: migraine; Uncommon: vertigo, tremors, sleep disorders, cognitive function disorders and hyperesthesia ; Rare: disorders of equilibrium, decreased consciousness, confusion, sedation, coordination disorders, neuritis, dreams, altered sense of taste, motor retardation, muscle twitching, fasciculation and convulsions.

Opththalmologic

Uncommon: photophobia; Rare: eye hemorrhage, dry eyes and difficulty focusing.

Psychiatric

Uncommon: anxiety and depressive disorders; Rare: aggression, agitation and detachment.

Sexual Function/Reproduction

Rare: lumps of female reproductive tract and inflammation of the fallopian tube.

Skin

Uncommon: skin photosensitivity, rashes, pruritis, sweating and urticaria; Rare: erythema, dermatitis, dermatosis, pruritic skin rash, hair loss and alopecia.

Urologic

Uncommon: urinary infections; Rare: urinary tract hemorrhage, urinary urgency and pyelitis.

Post-Market Adverse Drug Reactions

The following section enumerates potentially important adverse events that have occurred in clinical practice and that have been reported spontaneously to various surveillance systems. The events enumerated represent reports arising from both domestic and nondomestic use of naratriptan. These events do not include those already listed in the ADVERSE REACTIONS section above. Because the reports cite events reported spontaneously from worldwide postmarketing experience, frequency of events and the role of naratriptan in their causation cannot be reliably determined.

General

Hypersensitivity, including anaphylaxis/anaphylactoid reactions, in some cases severe (e.g., circulatory collapse) (see WARNINGS AND PRECAUTIONS).

Cardiovascular

Angina, myocardial infarction, peripheral vascular ischemia, cerebral vascular accident, including transient ischemic attack, subarachnoid hemorrhage and, cerebral infarction (see WARNINGS AND PRECAUTIONS).

Gastrointestinal

Colonic ischemia (see WARNINGS AND PRECAUTIONS).

Neurologic

Somnolence (see WARNINGS AND PRECAUTIONS).

Respiratory

Dyspnea (see WARNINGS AND PRECAUTIONS).

Drug Interactions

Overview

The limited metabolism of AMERGE and the wide range of cytochrome P450 isoenzymes involved, as determined by in vitro studies, suggest that significant drug interactions with AMERGE are unlikely. AMERGE did not inhibit monoaminase oxidase (MAO-A or MAO-B) in vitro. The possibility of pharmacodynamic in vivo interactions between AMERGE and monoaminase oxidase inhibitors has not been investigated.

Drug-Drug Interactions

Ergot-Containing Drugs

Ergot-containing drugs have been reported to cause prolonged vasospastic reactions. Because there is a theoretical basis for these effects being additive, ergot-containing or ergot-type medications (e.g. dihydroergotamine or methysergide) are contraindicated within 24 hours of AMERGE administration (see CONTRAINDICATIONS).

Other 5-HT1 Agonists

The administration of AMERGE with other 5-HT1 agonists has not been evaluated in migraine patients. As an increased risk of coronary vasospasm is a theoretical possibility with co-administration of 5-HT1 agonists, use of these drugs within 24 hours of each other is contraindicated (see CONTRAINDICATIONS).

Selective Serotonin Reuptake Inhibitor (SSRIs)/Serotonin Norepinephrine Reuptake Inhibitors (SNRIs)

Cases of life threatening serotonin syndrome have been reported during combined use of selective serotonin reuptake inhibitors (SSRIs) or serotonin norepinephrine reuptake inhibitors (SNRIs) and triptans (see WARNINGS AND PRECAUTIONS).

Hormonal Contraceptives

In a population pharmacokinetic study in migraine patients, hormonal contraceptive use was associated with a 32% decrease in naratriptan clearance.

Drug-Food Interactions

Alcohol and Food

Clinical studies did not reveal any pharmacokinetic interaction when naratriptan was administered together with alcohol or food.

Drug-Lifestyle Interactions

Tobacco

In a population pharmacokinetic study in migraine patients, tobacco use was associated with a 29% increase in naratriptan clearance.

Drug-Laboratory Interactions

AMERGE is not known to interfere with commonly employed clinical laboratory tests.

Dosage and Administration

Dosing Considerations

  • AMERGE is recommended only for the acute treatment of migraine attacks. AMERGE should not be used prophylactically.
  • The safety of treating, on average, more than four headaches in a 30 day period has not been established.
  • If a patient does not respond to the first dose of AMERGE, a second dose should not be taken for the same attack, as it is unlikely to be of benefit.
  • AMERGE can be taken with or without food.

Recommended Dose and Dosage Adjustment

Adults

The minimal effective single adult dose of AMERGE Tablets is 1 mg. The maximum recommended single dose is 2.5 mg, which should not be exceeded (see CLINICAL TRIALS).

Table 2 Percentage of Patients with Headache Relief at 4 Hours Post-Dosing
Placebo AMERGE 1 mg AMERGE 2.5 mg
% (N) % (N) % (N)
Study 1 39 (91) 64 (85) 63 (87)
Study 2 34 (122) 50* (117) 60* (127)
Study 3 27 (107) 52* (219) 66*M (209)
Study 4 33 (602) 57* (595) 68*M (586)

Pain relief is defined as a reduction in headache severity from grade 3 or 2 (severe or moderate) to grade 1 or 0 (mild or no pain)

Comparison between 1 mg and 2.5 mg AMERGE doses was not performed

*p<0.05 versus placebo

Mp<0.01 versus AMERGE 1 mg

In 3 of the 4 studies, optimal rates of headache relief were achieved with a 2.5 mg dose. As patients may vary in their dose-responsiveness, the choice of dose should be made on an individual basis, weighing the possible benefit of the 2.5 mg dose with the potential for a greater risk of adverse events.

Administration

AMERGE tablets should be swallowed whole with water. AMERGE should be taken as early as possible after the onset of a migraine headache, but is effective if taken at a later stage.

Redosing

If the migraine headache returns, or if a patient has a partial response, the initial dose may be repeated once after 4 hours, for a maximum dose of 5 mg in a 24 hours period.

Special Populations

Renal Impairment

Renal disease/functional impairment causes prolongation of the half-life of orally administered AMERGE. Consequently, if treatment is deemed advisable in the presence of renal impairment, a maximum single dose of 1 mg should be administered. No more than a total of 2 mg should be taken in any 24 hour period. Repeated dosing in renally impaired patients has not been evaluated (see ACTION AND CLINICAL PHARMACOLOGY). Administration of AMERGE in patients with severe renal impairment (creatinine clearance <15 mL/min) is contraindicated (see CONTRAINDICATIONS).

Hepatic Impairment

Hepatic disease/functional impairment causes prolongation of the half-life of orally administered AMERGE. Consequently, if treatment is deemed advisable in the presence of hepatic impairment, a maximum single dose of 1 mg should be administered. No more than a total of 2 mg should be taken in any 24 hour period (see ACTION AND CLINICAL PHARMACOLOGY). Administration of AMERGE tablets in patients with severe hepatic impairment (Child-Pugh grade C) is contraindicated (see CONTRAINDICATIONS).

Hypertension

AMERGE should not be used in patients with uncontrolled or severe hypertension. Patients with mild to moderate controlled hypertension should be treated cautiously at the lowest effective dose.

Overdosage

For management of a suspected drug overdose, contact your regional Poison Control Centre.

In clinical studies, numerous patients (n=222) and healthy subjects (n=196) have received AMERGE at doses of 5 to 25 mg. In the majority of cases, no serious adverse events were reported. One patient treated with a 7.5 mg dose experienced ischemic ECG changes, which were likely due to coronary vasospasm. This event was not associated with a serious clinical outcome. A patient who was mildly hypertensive experienced a significant increase in blood pressure (baseline value of 150/98 to 204/144 mmHg at 225 minutes) beginning 30 minutes after the administration of a 10 mg dose (4 times the maximum recommended single dose). The event resolved with antihypertensive treatment. Administration of 25 mg (10 times the maximum recommended single dose) in one healthy male subject increased blood pressure from 120/67 mmHg pre-treatment up to 191/113 mmHg at approximately 6 hours post-dose and resulted in adverse events including lightheadedness, tension in the neck, tiredness and loss of coordination. Blood pressure returned to near baseline by 8 hours after dosing without any pharmacological intervention.

The elimination half-life of naratriptan is about 5 to 8 hours (see ACTION AND CLINICAL PHARMACOLOGY), and therefore monitoring of patients after overdose with AMERGE Tablets should continue for at least 24 hours of longer if symptoms or signs persist. Standard supportive treatment should be applied as required. If the patient presents with chest pain or other symptoms consistent with angina pectoris, electrocardiogram monitoring should be performed for evidence of ischemia. Appropriate treatment (e.g. nitroglycerin or other coronary artery vasodilators) should be administered as required.

It is unknown what effect hemodialysis or peritoneal dialysis has on the serum concentrations of AMERGE.

Action and Clinical Pharmacology

Mechanism of Action

Naratriptan has been demonstrated to be a selective agonist for a vascular 5-hydroxytryptamine receptor subtype (probably a member of the 5-HT1B/1D family) with little or no binding affinity for 5-HT2/3 receptor subtypes alpha1-, alpha2- or beta-adrenergic; dopamine1; dopamine2; muscarinic; or benzodiazepine receptors. Naratriptan did not exhibit agonist or antagonist activity in ex vivo assays of 5-HT4 and 5-HT7 receptor-mediated activities. The therapeutic activity of AMERGE in migraine is generally attributed to its agonist activity at 5-HT1B/5-HT1D receptors. Two current theories have been proposed to explain the efficacy of 5-HT1 receptor agonists in migraine. One theory suggests that activation of 5-HT1 receptors located on intracranial blood vessels, including those on the arteriovenous anastomoses, leads to vasoconstriction, which is believed to be correlated with the relief of migraine headache. The other hypothesis suggests that activation of 5-HT1 receptors on perivascular fibres of the trigeminal system results in the inhibition of pro-inflammatory neuropeptide release. These theories are not mutually exclusive.

Pharmacokinetics

Absorption

Naratriptan is well absorbed, with 74% oral bioavailability in females and 63% in males. After oral administration, the absorption is rapid and peak concentrations are obtained in 2 to 5 hours. A two-period crossover study was performed in 15 female migraine patients who received AMERGE as a single 2.5 mg tablet during a migraine attack, followed 3-7 days later by another 2.5 mg treatment during a non-migraine period. During a migraine attack, absorption is slower, although exposure (AUC) and elimination half-life are not significantly affected.

Table 3  Pharmacokinetic Parameters in Female Migraine Patients after receiving 2.5 mg AMERGE Tablets*
Parameter Migraine Attack
(N=15)
Non-Migraine Period
(N=15)
Cmax (ng/mL) 7.66 (3.07) 9.50 (3.63)
tmax (h) 3.8 (2.1) 2.0 (1.0)
AUC (ng/mL.h) 86.7 (32.5) 92.0 (33.7)
Cl/F (mL/min) 467.5 (126.4) 520.7 (222.6)
t1/2 (h) 6.75 (1.44) 7.02 (2.39)

*values quoted are arithmetic mean (standard deviation)

Cmax - maximum concentrations  tmax - time to maximum concentration

Cl/f - apparent clearance  t1/2 - elimination half-life

AUC - area under the curve of concentration vs time extrapolated to infinity

Plasma levels of naratriptan increase in a dose-proportional manner consistent with linear pharmacokinetics over a 1 to 10 mg dose range. The absorption and elimination are independent of the dose. Administration with food does not appreciably influence the pharmacokinetics of naratriptan. Repeat administration of AMERGE (up to 10 mg once daily for 5 days) does not result in drug accumulation.

Distribution

According to a population pharmacokinetics estimate, naratriptan is distributed into a volume of approximately 261 L. Plasma protein binding is low (29%).

Metabolism

In vitro, naratriptan is metabolized by a wide range of cytochrome P450 isoenzymes into a number of inactive metabolities. Naratriptan is a poor inhibitor of cytochrome P450 isoenzymes, and does not inhibit monoamine oxidase (MAO) enzymes; metabolic interactions between naratriptan and drugs metabolized by P450 or MAO are, therefore, unlikely.

Excretion

The elimination half-life generally ranges from 5-8 hours. Oral clearance is 509 mL/min in females and 770 mL/min in males. The renal clearance (220 mL/min) exceeds the glomerular filtration rate, suggesting that the drug undergoes active tubular secretion. Naratriptan is predominantly eliminated in urine, with 50% of the dose recovered unchanged and 30% as metabolites.

Special Populations and Conditions

Geriatrics

A study was performed to compare the pharmacokinetics of naratriptan in young (6 female/6 male, 24-44 years of age) and elderly (6 female/6 male, 65-77 years of age) subjects. The subjects received two doses each of placebo, 1 mg naratriptan and 2.5 mg naratriptan separated by 4 hour intervals. A minimum 96 hour period intervened between consecutive treatment days.

Elderly patients experienced a higher degree of exposure to naratriptan than did younger subjects. Mean Cmax and area under the plasma concentration time curve values were 28% and 38% higher, respectively, for the 1 mg treatment group and 15% and 32% higher, respectively, for the 2.5 mg group. Total and renal clearance were decreased by about 30%, while the elimination half-life was increased by about 1 hour.

Elevations in systolic blood pressure at the 2.5 mg dose were more pronounced in the elderly subjects than in the young subjects (mean peak increases 12 mmHg in elderly versus 2 mmHg in young subjects).

Hepatic Impairment

Liver metabolism plays a limited role in the clearance of naratriptan. The pharmacokinetics of a single 2.5 mg dose of naratriptan were determined in subjects with moderate hepatic impairment (Child-Pugh grade A or B, n=8) and gender- and age-matched healthy subjects (n=8). Subjects with hepatic impairment showed a moderate decrease in clearance (approximately 30%) resulting in increases of approximately 40% in the half-life (range, 8 to 16 hours) and the area under the plasma concentration time curve (see DOSAGE AND ADMINISTRATION).

Renal Impairment

Renal excretion is the major route for elimination of naratriptan. A study to compare male and female subjects with mild to moderate renal impairment (n=15; 31-58 years of age, screening creatinine clearance: median 41.2 mL/min, range 18 to 115 mL/min) to gender-matched healthy subjects (n=8, 21-47 years of age) showed a decrease in oral clearance (mean decreased by 50%) resulting in a longer mean half-life (approximately 11 hours, range, 7 to 20 hours) and an increase in the mean Cmax (approximately 40%). In this study, blood pressure measurements suggested that increased exposure in renally-impaired subjects may be associated with increases in blood pressure, which are larger than those seen in healthy subjects receiving the same dose (5 mg) (see DOSAGE AND ADMINISTRATION).

Storage and Stability

AMERGE should be stored below 30°C.

Dosage Forms, Composition and Packaging

Availability of Dosage Form

AMERGE 2.5 mg Tablets are green film-coated, D-shaped tablets with GXCE5 embossed on one side. Available in blister packs of 2 or 6 tablets.

AMERGE 1 mg Tablets are white film-coated, D-shaped tablets with GXCE3 embossed on one side. Available in blister packs of 2 tablets.

Composition

AMERGE Tablets contain 1 or 2.5 mg of naratriptan (base) as the hydrochloride salt and the following nonmedicinal ingredients: croscarmellose sodium, hydroxypropyl methylcellulose, indigo carmine aluminium lake (FD&C Blue No. 2) [2.5 mg tablet only] , iron oxide yellow [2.5 mg tablet only] , lactose, magnesium stearate, microcrystalline cellulose, titanium dioxide, and triacetin.