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

Manufacture: Roche
Country: Canada
Condition: Parkinson's Disease, Restless Legs Syndrome
Class: Antiparkinson agents
Form: Capsules
Ingredients: Levodopa, Benserazide, Gelatin, Indigotine, Iron oxide, Magnesium stearate, Mannitol (50-12.5 capsule only), Microcrystalline cellulose, Povidone, Talc, Titanium dioxide

Levodopa and Benserazide Combination

Summary Product Information

Route of
Administration
Dosage Form / Strength Non-medicinal Ingredients
(alphabetical order)
Oral Capsule
50-12.5, 100-25, 200-50
Gelatin, indigotine, iron oxide,
magnesium stearate, mannitol (50-12.5
capsule only), microcrystalline cellulose,
povidone, talc, titanium dioxide.

Indications and Clinical Use

Adults (> 25 years of age)

PROLOPA (levodopa and benserazide combination) is indicated for the treatment of Parkinson’s disease with the exception of drug-induced parkinsonism.

The administration of PROLOPA is associated with amelioration of the symptoms of Parkinson’s disease with the advantage that combined therapy significantly diminishes the incidence of the levodopa-induced peripheral side-effects of nausea, vomiting and possibly cardiac arrhythmias.

This results in an advantage for those patients who previously were unable to tolerate an optimal daily dosage of levodopa. Improved gastrointestinal tolerance also provides for a more rapid induction of therapy, e.g., optimum dosage can in most cases be achieved within two to three weeks.

However, combined therapy with levodopa and benserazide increases the incidence of centrally mediated abnormal movements earlier in therapy and can lead to an earlier appearance of oscillations in performance. Thus, when combined therapy with levodopa and benserazide is instituted it is important to strive at using and maintaining a dosage regimen which balances efficacy with freedom from dyskinesias.

Despite the dramatic symptomatic improvement it produces in many patients with Parkinson’s disease, levodopa does not arrest the progression of the disease and there is evidence to indicate that drug adverse effects increase with continuing use. Combined therapy, because of the advantages already described, is therefore indicated only when its use is capable of improving the quality of life of the patient. However, there is little to be gained by substituting combined therapy for levodopa in patients already on stable, effective and well-tolerated levodopa therapy.

Pediatrics and Young Adults (<25 years of age)

The safety and effectiveness of PROLOPA have not been established in these populations. Animal studies have suggested the possibility of skeletal abnormalities when beserazide is administered before ossification is complete. Therefore PROLOPA must not be given to patients less than 25 years of age (see Contraindications and Warnings and Precautions).

Contraindications

As with levodopa, PROLOPA should not be given when administration of a sympathomimetic amine is contraindicated (e.g., epinephrine, norepinephrine or isoproterenol).

Monoamine oxidase inhibitors cannot be given concomitantly and should be withdrawn at least two weeks prior to initiating therapy with PROLOPA, otherwise, unwanted effects such as hypertensive crises are likely to occur.

PROLOPA is contraindicated in patients with clinical or laboratory evidence of uncompensated cardiovascular, endocrine, renal, hepatic, hematologic, or pulmonary disease. PROLOPA is also contraindicated in patients with narrow angle glaucoma.

PROLOPA is contraindicated in patients with a known hypersensitivity to levodopa, benserazide or to any ingredient in the formulation or component of the container. For a complete listing, see the Dosage Forms, Composition and Packaging section of the product monograph.

PROLOPA is contraindicated in patients with decompensated endocrine, renal or hepatic function, cardiac disorders, psychiatric diseases with a psychiatric component or closed angle glaucoma.

PROLOPA is contraindicated in patients less than 25 years old (skeletal development must be complete)(see Warnings and Precautions).

PROLOPA is contraindicated in pregnant women or to women of childbearing potential in the absence of adequate contraception. If pregnancy occurs in a woman taking PROLOPA, the drug must be discontinued via tapering, as advised by the prescribing physician. PROLOPA must not be withdrawn abruptly (see Warnings and Precautions, Neurologic, Neuroleptic Malignant Syndrome).

Warnings and Precautions

Serious Warnings and Precautions

Patients receiving treatment with PROLOPA (levodopa and benserazide combination) and other dopaminergic agents have reported suddenly falling asleep while engaged in activities of daily living, including the driving of a car, which has sometimes resulted in accidents. Although some of the patients reported somnolence while on PROLOPA, others perceived that they had no warning signs, such as excessive drowsiness, and believed that they were alert immediately prior to the event.

Physicians should alert patients of the reported cases of sudden onset of sleep, bearing in mind that these events are NOT limited to initiation of therapy. Patients should also be advised that sudden onset of sleep has occurred without warning signs and should be specifically asked about factors that may increase the risk with PROLOPA such as concomitant medications or the presence of sleep disorders. Given the reported cases of somnolence and sudden onset of sleep (not necessarily preceded by somnolence), physicians should caution patients about the risk of operating hazardous machinery, including driving motor vehicles, while taking PROLOPA. If drowsiness or sudden onset of sleep should occur, patients should be informed to immediately contact their physician.

Episodes of falling asleep while engaged in activities of daily living have also been reported in patients taking other dopaminergic agents, therefore, symptoms may not be alleviated by substituting these products.

Currently, the precise cause of this event is unknown. It is known that many Parkinson ́s disease patients experience alterations in sleep architecture, which results in excessive daytime sleepiness or spontaneous dozing, and that dopaminergic agents can also induce sleepiness. There is insufficient information to determine whether this event is associated specifically with PROLOPA, all dopaminergic agents, or Parkinson ́s disease itself.

General

Before initiating therapy in patients already receiving levodopa, this drug should be discontinued at least 12 hours before PROLOPA (levodopa and benserazide combination) is started. Therapy with PROLOPA should be instituted at a level that will provide approximately 15% of the previous dosage of levodopa.(see Dosage and Administration).

Regular assessment of cardiovascular, hepatic, hematopoietic and renal function should be performed in all patients during the dosage stabilization period.

Hypersensitivity reactions may occur in susceptible individuals.

Patients with severe parkinsonism who improve on therapy with PROLOPA should be advised to resume normal activities gradually and with caution as rapid mobilization may increase the risk of injury, especially in those patients with osteoporosis or phlebothrombosis. Physiotherapy and appropriate safeguards may be useful during this phase.

Cardiovascular

Care should be exercised in administering PROLOPA to patients with a history of myocardial infarction or who have atrial, nodal or ventricular arrhythmias. Patients with cardiac abnormalities should have their treatment with PROLOPA initiated in a facility with adequate monitoring equipment and provision for intensive care.

Dependence/Tolerance/Abuse

PROLOPA may induce dopamine dysregulation syndrome (DDS) resulting in excessive use of the product: A small number of patients suffer from cognitive and behavioural disturbance that can be directly attributed to taking increasing quantities of dopaminergic medication against medical advice and well beyond the dose required to treat their motor disabilities.

Endocrine and Metabolism

Patients with diabetes should undergo frequent blood sugar tests, and the dosage of antidiabetic agents should be adjusted to blood sugar levels.

Gastrointestinal

The possibility of upper gastrointestinal hemorrhage occurring in patients with a history of peptic ulcer must be borne in mind when treating them with PROLOPA.

Neurologic

PROLOPA is not indicated in the management of intention tremor, Huntington’s chorea, or drug-induced extrapyramidal effects.

Since PROLOPA may induce central nervous system side effects shortly after beginning its use, and at lower doses than levodopa, it is important to administer the dosage in careful increments and to observe patients carefully for the development of abnormal involuntary movements. These movements and oscillations in performance may appear earlier with combination therapy. Should they occur, a reduction of dosage is indicated.

Patients with a history of convulsive disorders should be treated cautiously if PROLOPA is incorporated into their treatment regimen.

Neuroleptic Malignant-like Syndrome

PROLOPA must not be withdrawn abruptly. A symptom complex resembling the neuroleptic malignant syndrome, characterized by elevated temperature, muscular rigidity, altered consciousness, autonomic instability, possible psychological changes and elevated serum creatinine phosphokinase has been reported in association with rapid dose reduction, withdrawal of, or changes in antiparkinsonian therapy. Therefore, withdrawal of treatment should proceed slowly and patients should be monitored carefully when the dosage of PROLOPA is reduced or discontinued. Should a combination of such symptoms occur, the patient should be kept under medical surveillance, hospitalized if necessary, and appropriate symptomatic treatment given. This may include resumption of therapy with PROLOPA after appropriate evaluation.

Ophthalmologic

Patients with chronic wide-angle glaucoma can be treated cautiously with PROLOPA, provided the intraocular pressure is well controlled. The intraocular pressure should be monitored carefully during therapy as levodopa theoretically has the potential to raise intraocular pressure. Rarely pupillary dilatation and activation of latent Horner’s syndrome have been reported during levodopa treatment.

Peri-Operative Considerations

If a patient on levodopa requires general anesthetics, the normal PROLOPA regimen should be continued as close to surgery as possible, except in the case of halothane.

In general anesthesia with halothane, PROLOPA should be discontinued 12-48 hours before surgical interventions as fluctuations in blood pressure and/or arrhythmias may occur in patients being treated with PROLOPA. Therapy with PROLOPA may be resumed following surgery; the dosage should be increased gradually to the preoperative level.

Psychiatric

Depression may occur in patients treated with PROLOPA, but may also be an effect of the underlying disease. All patients should be carefully observed for signs of depression with suicidal tendencies or other serious behavioural changes. Extreme caution should be used in treating patients with a history of psychotic disorders or who are receiving psychotherapeutic agents such as reserpine, phenothiazines or tricyclic antidepressants.

Psychomotor Performance

Patients being treated with levodopa and presenting with somnolence and/or sudden onset sleep episodes should be advised to refrain from driving or engaging in activities where impaired alertness may put themselves or others at risk of serious injury or death (e.g., operating machines) until such recurrent episodes and somnolence have resolved (see WARNINGS AND PRECAUTIONS: Serious Warnings and Precautions).

Behavioural Changes

Patients and caregivers should be advised to adhere to dosage instructions given by the physician. Patients should be regularly monitored for the development of impulse control disorders. Patients and caregivers should be made aware that behavioral symptoms of impulse control disorders, including pathological (compulsive) gambling, hypersexuality, increased libido, compulsive spending/buying, and compulsive eating (binge), have been reported in patients treated with dopamine agonists for Parkinson's disease (see Adverse Reactions). Although PROLOPA is not a dopamine agonist, caution is advised as PROLOPA is a dopaminergic drug and patients should be monitored for the development of impulse control disorders. Literature and postmarketing reports have described a very rare addictive pattern of dopamine replacement therapy, in which patients use doses in excess of those required to control their motor symptoms. Review of treatment is recommended if such symptoms develop.

Hallucinations

Hallucinations and confusion are known side effects of treatment with dopaminergic agents, including levodopa. Patients should be aware of the fact that hallucinations (mostly visual) can occur.

Skin

Care should be exercised in administering this drug to patients with a history of melanoma or with suspicious undiagnosed skin lesions.

Epidemiological studies have shown that patients with Parkinson’s disease have a higher risk (2-to approximately 6-fold higher) of developing melanoma than the general population. Whether the increased risk observed was due to Parkinson’s disease or other factors, such as drugs used to treat Parkinson’s disease, is unclear. For the reasons stated above, patients and healthcare providers are advised to monitor for melanomas frequently and on a regular basis when using PROLOPA for any indication. Ideally, periodic skin examinations should be performed by appropriately qualified individuals (e.g., dermatologists).

Special Populations

Pregnant Women

Although the effects of PROLOPA on human pregnancy are unknown, levodopa has caused visceral and skeletal malformations in rabbits (see TOXICOLOGY: Teratologic and Reproductive Studies). Therefore, PROLOPA is completely contraindicated during pregnancy and in women of childbearing potential in the absence of adequate contraception (see Contraindications).

Nursing Women

It is not known whether benserazide passes into breast milk. Mothers requiring treatment with PROLOPA should not nurse their infants, since the occurrence of skeletal malformations in infants cannot be excluded.

Pediatrics and Young Adults (<25 years of age)

The safety and effectiveness of PROLOPA have not been established in these populations. Animal studies have suggested the possibility of skeletal abnormalities when benserazide is administered before ossification is complete. Therefore PROLOPA must not be given to patients less than 25 years of age (see Contraindications).

It should also be borne in mind that PROLOPA stimulates human growth hormone secretion.

Monitoring and Laboratory Tests

Liver and kidney function tests and monitoring of blood cell counts should be performed during the dosage stabilization period and periodically during extended treatment.

Patients with diabetes should undergo frequent blood sugar tests, and the dosage of antidiabetic agents should be adjusted to blood sugar levels.

Adverse Reactions

Adverse Drug Reaction Overview

The most common serious adverse reactions occurring with PROLOPA (levodopa and benserazide combination) are abnormal involuntary movements and dyskinesias. Dosage reduction can diminish those reactions though often at the expense of increasing parkinsonism. Other serious adverse reactions are oscillations in performance, psychiatric disorders and, less frequently, cardiovascular effects.

Involuntary Movements

Choreiform, dystonic, athetotic and other involuntary movements. Muscle twitching and blepharospasm occur less often and may be taken as early signs of overdosage. The appearance of these reactions can usually be eliminated or made tolerable by adjusting the dosage and by giving smaller single doses more frequently. The incidence of involuntary movements reported by several investigators was 30% to 40% in the first month and 50% to 60% or more by six to nine months.

Oscillations in Performance

Periodic oscillations in performance constitute the most serious problem encountered after prolonged levodopa therapy and appear earlier with combined therapy than when levodopa is used alone. Three types have been described:

  • End-of-dose akinesia: episodic re-emergence of Parkinsonian symptoms three or more hours after each dose of levodopa, often following a period of dyskinesia. This type of akinesia tends to occur progressively earlier after each dose during prolonged therapy and is regarded as resulting from a temporary insufficiency of dopamine at the appropriate receptor sites.
  • On-off phenomenon: a rapid alternation between a state of satisfactory motility, usually with oral-facial dyskinesias and a rigid akinetic state without dyskinesias. This oscillation of performance is also regarded as being associated with a temporary insufficiency of dopamine.
  • Akinesia paradoxica (hypotonic freezing): irregular episodes of sudden freezing, usually short duration, with the patient unable to move, accompanied by hypotonia and postural instability. These episodes are at times accompanied by autonomic symptoms. Hypotonic freezing is regarded as possibly associated with a severe temporary deficiency in noradrenaline in progressively depleted and damaged noradrenaline pathways.

Psychiatric Disorders

Paranoid ideation, psychotic episodes, depression (with or without development of suicidal tendencies) and dementia. In depressed patients, levodopa may give rise to an improvement in mood in a small number of individuals. However, when administered to patients with bipolar depression, it tends regularly to produce hypomania. Various psychiatric disturbances have been reported in about 20% of patients.

Gastrointestinal Effects

Undesirable gastrointestinal effects, which may occur mainly in the early stages of the treatment, can largely be controlled by taking PROLOPA with a small snack (e.g., biscuits) or liquid, or by increasing the dose slowly.

Other adverse reactions that have been reported less frequently are

Cardiovascular: arrhythmias, flushing and angina pectoris

Dermatologic: dark sweat, sweating, edema, hair loss, pallor, rash, pruritus

Gastrointestinal: nausea and vomiting, constipation, diarrhea, epigastric and abdominal distress or pain, flatulence, eructation, hiccups, sialorrhea, difficulty in swallowing, bitter taste, dry mouth, duodenal ulcer, gastrointestinal bleeding, burning sensation of the tongue

General: fever, fatigue and malaise

Genitourinary: dark urine, hematuria, nocturia and urinary frequency, retention or incontinence and changes in pbido

Hematologic: hemolytic anemia, transient leukopenia, agranulocytosis, thrombocytopenia

Investigations: non-specific ECG changes, weight variation, body fluids or tissues may be discoloured or stained including sapva, the tongue, teeth or oral mucosa

Metabopc and Nutritional: anorexia

Musculoskeletal: low back pain, muscle spasm and twitching, musculoskeletal pain

Neurologic: ataxia, faintness, impairment of gait, headache, increased hand tremor, akinetic episodes, torticolps, trismus, tightness of the mouth, pps or tongue, oculogyric crisis, weakness, numbness, bruxism and convulsions, loss of taste

Ophthalmologic: blurred vision, diplopia, dilated pupils, activation of latent Horner’s syndrome

Psychiatric: increased pbido with serious antisocial behaviour, euphoria, lethargy, sedation, stimulation, confusion, insomnia, nightmares, hallucinations and/or delusions, agitation, temporal disorientation and anxiety, somnolence and very rarely excessive daytime somnolence and sudden sleep onset episodes. Agitation, anxiety, insomnia, hallucinations, delusions and temporal disorientation may occur particularly in elderly patients and in patients with a history of such disorders. Dopamine dysregulation syndrome (DDS) has been reported.

Respiratory: cough, hoarseness, bizarre breathing pattern, post nasal drip

Skin: pruritus, rash

Urogenital: urine discoloration

Vascular: orthostatic hypotensive episodes, hypertension, phlebitis

Progressive impairment of intellectual and autonomic functions has been described, particularly in akinetic patients, after prolonged levodopa therapy.

Pathological (compulsive) gambling has been reported in post-marketing data, including those in the literature, for antiparkinsoninan drugs. Sporadic cases of pathological (compulsive) gambling have been reported in patients treated with dopaminergic agents including levodopa. Dosage adjustments should be considered in the management of this behaviour.

Abnormal Hematologic and Clinical Chemistry Findings

Elevations of BUN, serum uric acid, SGOT, SGPT, LDH, bilirubin, alkaline phosphatase or PBI have been observed. Increase of GGT has also been reported. Positive Coombs’ tests have been observed during extended therapy, both with PROLOPA and with levodopa alone but hemolytic anemia is extremely rare.

Drug Interactions

Drug-Drug Interactions

Cardiovascular Drugs

Postural hypotensive episodes have been reported; therefore, PROLOPA (levodopa and benserazide combination) should be administered cautiously and blood pressure monitored in patients on antihypertensive medication. It may be necessary to adjust the dosage of the latter particularly during the initial stages of therapy with PROLOPA. Antihypertensive medications containing reserpine inhibit the action of PROLOPA.

MAO Inhibitors

See Contraindictions.

Psychoactive Drugs

If concomitant administration of psychoactive drugs is necessary, they should be administered with great caution. Patients should be carefully observed for unusual untoward drug effects (see CONTRAINDICATIONS and WARNINGS AND PRECAUTIONS: Psychiatric).

Antipsychotics

Concomitant administration of antipsychotics with dopamine receptor blocking properties, particularly D2 receptor antagonists (e.g., phenothiazines, butyrophenones and risperidone), may reduce the therapeutic effects of levodopa and should be used with caution. Patients taking these medications together with PROLOPA should be observed carefully for loss of therapeutic response or worsening of parkinsonian symptoms.

Anesthetics

If a patient on levodopa requires general anesthetics, the normal PROLOPA regimen should be continued as close to surgery as possible, except in the case of halothane (see Warnings and Precautions).

PROLOPA should be discontinued 12-48 hours before surgical intervention requiring general anesthesia with halothane as fluctuations in blood pressure and/or arrhythmias may occur in patients being treated with PROLOPA. Therapy with PROLOPA may be resumed following surgery; the dosage should be increased gradually to the preoperative level (see Warnings and Precautions).

Sympathomimetics

PROLOPA should not be administered concomitantly with sympathomimetics (agents such as epinephrine, norepinephrine, isoproterenol or amphetamine which stimulate the sympathetic nervous system) as levodopa may potentiate their effects (see CONTRAINDICATIONS). Should concomitant administration prove necessary, close surveillance of the cardiovascular system is essential, and the dose of the sympathomimetic agents may need to be reduced.

Trihexyphenidyl

Coadministration of the anticholinergic drug trihexyphenidyl with PROLOPA reduces the rate, but not the extent, of levodopa absorption.

Ferrous Sulphate

Ferrous sulphate decreases the maximum plasma concentration and the AUC of levodopa by 30% to 50%. The pharmacokinetic changes observed during co-treatment with ferrous sulphate appear to be clinically significant in some but not all patients.

Isoniazid

Isoniazid may reduce the therapeutic effects of levodopa.

Phenytoin and papaverine

The beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with PROLOPA should be carefully observed for loss of therapeutic response.

Metoclopramide

Although metoclopramide may increase the bioavailability of levodopa by increasing gastric emptying, metoclopramide may also adversely affect disease control by its dopamine receptor antagonistic properties.

Domperidone

May increase the bioavailability of levodopa by stimulation of gastric emptying.

Other Anti-Parkinsonian Agents

Combination with other anti-parkinsonian agents (e.g. anticholinergics, amantadine, dopamine agonists, bromocriptine and selegiline) is permissible, though both the desired and undesired effects of treatment may be intensified. It may be necessary to reduce the dosage of PROLOPA or the other substance. When initiating an adjuvant treatment with a COMT inhibitor, a reduction of the dosage of PROLOPA may be necessary. Anticholinergics should not be withdrawn abruptly when therapy with PROLOPA is instituted, as levodopa does not begin to take effect for some time.

Drug-Food Interactions

Since certain amino acids can compete with the absorption of levodopa, the absorption of levodopa may be impaired and its effects may be diminished when administered with a protein-rich meal in some patients.

Taking PROLOPA with a small snack (e.g., biscuits) or liquid does not impair absorption and may help to control gastrointestinal side effects.

Drug-Herb Interactions

No Drug-Herb interactions have been established.

Drug-Laboratory Test Interactions

Levodopa may affect the results of laboratory tests for catecholamines, creatinine, uric acid and glucose. The urine test results can be false positive for ketone bodies.

Dosage and Administration

Dosing Considerations

General

In order to achieve maximal benefit and reduce the incidence of adverse reactions, therapy with PROLOPA (levodopa and benserazide combination) should be introduced gradually and must be individualized. Drug administration must be continuously matched to the needs and tolerance of the patient. The following dosing instructions should therefore be regarded as guidelines. Because of the increased availability of levodopa to the central nervous system when administered in combined therapy, titration and adjustments of dosage should be made in small steps and the dosage ranges recommended should usually not be exceeded. The appearance of involuntary movements should be regarded as a sign of levodopa toxicity and as an indication of overdosage, usually requiring a reduction in dosage. Treatment should aim at maximal benefit without dyskinesias. Patients should be carefully observed for possible undesirable psychiatric symptoms (see Warnings and Precautions: Psychiatric).

Levodopa should be discontinued for at least twelve (12) hours before initiating therapy with PROLOPA (see Warnings and Precautions: General).

PROLOPA must not be withdrawn abruptly, due to risk of neuroleptic malignant syndrome (see Warnings and Precautions:, Neurologic, Neuroleptic Malignant Syndrome).

Geriatrics

Dosage must be carefully titrated in the elderly.

Pediatrics and Young Adults (< 25 years of age)

The safety and effectiveness of PROLOPA have not been established in these populations (see Contraindications and Warnings and Precautions).

Recommended Dose and Dosage Adjustment

Initiation of Treatment in Patients Not on Levodopa Therapy

The initial recommended dose is one capsule of PROLOPA 100-25 once or twice a day. This dose may be carefully increased by one capsule every third or fourth day until an optimal therapeutic effect is obtained without dyskinesias. Near the upper limits of dosage, the increments should be made slowly, at two to four week intervals for example. The dosage should be divided, aiming at a frequency of dosing of at least four times daily taken with or immediately after meals. The optimal dosage for most patients is usually four to eight capsules of PROLOPA 100-25 daily (400 mg to 800 mg of levodopa) divided into four to six doses. Most patients require no more than six capsules of PROLOPA 100-25 (600 mg of levodopa) per day.

Individual patient response varies. Some patients, e.g., post-encephalitic Parkinson patients, may only tolerate a slower rate of increase in dosage, e.g., one capsule of PROLOPA 100-25 at weekly intervals, since these patients are more sensitive to levodopa and usually only tolerate lower dosages.

PROLOPA 200-50 capsules are intended only for maintenance therapy once the optimal dosage has been determined using PROLOPA 100-25 capsules. No patient should receive more than five to six capsules of PROLOPA 200-50 daily (1000 mg to 1200 mg of levodopa in combined therapy) during the first year of therapy.

Treatment should be continued for at least three to six weeks before it is concluded that therapy with PROLOPA has not benefited the patient.

Initiation of Treatment in Patients on Levodopa Therapy

Allow at least twelve (12) hours or more to elapse between the last dose of levodopa and the first dose of PROLOPA. A dosage of PROLOPA should be used that will provide approximately 15% of the previous levodopa daily dosage. For example, if a patient is receiving 4000 mg of levodopa per day, the dosage of PROLOPA 100-25 should not exceed six capsules (600 mg of levodopa) divided into four to six doses.

Adjustment and Maintenance of Therapy in All Patients

PROLOPA 200-50 capsules may be used for maintenance therapy once the optimal dosage has been determined using PROLOPA 100-25 capsules. PROLOPA 50-12.5 capsules should be used when frequent dosing is required to minimize adverse effects. During the first year of treatment, the total daily dosage should not exceed 1000 mg to 1200 mg of levodopa in combined therapy.

The variability in dosage response of patients is considerable. Some individuals may experience oscillations in performance with a diurnal rhythm of periods of symptomatic control alternating with periods of akinesia (end-of-dose), with return of Parkinson’s symptoms, which can frequently be corrected by re-scheduling individual doses. A low protein diet tends to potentiate and stabilize the effects of levodopa, whereas a high protein diet may decrease the effect of levodopa, although with combined therapy this effect may be less prominent. The predominant limiting factor in treatment with PROLOPA is the occurrence of involuntary movements. These frequently can be controlled by reducing the dosage of levodopa and varying the frequency of individual doses. A progressive decrease in the threshold for dyskinetic manifestations and an increase in the incidence of oscillations in performance have been reported after a certain time on levodopa therapy. These appear earlier in the course of combined treatment with PROLOPA than with levodopa alone.

In an attempt to avoid the emergence, or decrease the incidence of these manifestations, it is recommended that, after the initial period, the daily maintenance dosage of levodopa as combined therapy should be reduced slowly (at a rate of about 50 mg a month) over a period of a few months, to a maintenance level without dyskinesias. After one year of therapy, the patient should usually receive not more than six capsules of PROLOPA 100-25 daily (600 mg of levodopa) divided into at least four to six doses.

Other antiparkinson agents, e.g., anticholinergics, amantadine, and dopamine agonists may be continued during therapy with PROLOPA (although both the desired and undesired effects of treatment may be intensified) and should not be abruptly withdrawn. However, as treatment proceeds, their dosage may need to be altered (see Drug Interactions).

Interruption of Therapy

If therapy with PROLOPA is interrupted for a brief period, the previous dosage may be administered as soon as the patient is again able to take oral medication. If, however, therapy is interrupted for a longer period, a lower dosage should be given and the dosage should be adjusted gradually. In many cases, patients can be returned rapidly to their previous therapeutic dosage.

Administration

PROLOPA should be taken orally in divided doses.

It is recommended that the capsules be swallowed whole and not be opened or dissolved in liquid.

Overdosage

Symptoms and Signs

Symptoms and signs of overdose are qualitatively similar to the side effects of PROLOPA (levodopa and benserazide) in therapeutic doses but may be of greater severity. Overdose may lead to: cardiovascular side effects (e.g. cardiac arrhythmias), psychiatric disturbances (e.g. confusion and insomnia), gastro-intestinal effects (e.g. nausea and vomiting) and abnormal involuntary movements (see Warnings and Precautions: Neurologic).

Treatment

Monitor the patient’s vital signs and institute supportive measures as indicated by the patient’s clinical state. Intravenous fluids should be administered judiciously and an adequate airway maintained. Monitoring of respiratory function is recommended. It may be necessary to administer respiratory stimulants, or where appropriate, neuroleptics. ECG monitoring should be instituted and the patient carefully observed for the development of arrhythmias and if required appropriate anti-arrhythmic therapy should be provided. To date, the value of dialysis in the treatment of PROLOPA (levodopa and benserazide combination) overdosage is not known. Consideration should be given to the possibility of multiple drug ingestion by the patient. Pyridoxine is ineffective in reversing the effects of PROLOPA overdosage. For up-to-date information on the management of a suspected overdose, contact the regional Poison Control Center.

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

Action and Clinical Pharmacology

Mechanism of Action

The symptoms of Parkinson’s disease are to a high degree associated with striatal dopamine deficiency and degeneration of the dopamine containing neurons in the nigro-striatal bundle. Levodopa (INN) or L-DOPA (3,4-dihydroxy L-henylalanine) is an intermediate in dopamine biosynthesis. Levodopa (dopamine precursor) is used as a prodrug to increase dopamine levels since it is able to cross the blood-brain barrier whereas dopamine itself cannot. Once levodopa has entered the central nervous system (CNS), it is metabolized to dopamine by aromatic L-amino acid decarboxylase.

Levodopa, appears to correct the akinesia of Parkinson’s disease by the formation of dopamine at nigro-striatal dopaminergic sites that remain functional. While rigidity and tremor also improve with levodopa therapy, these symptoms seem to be related to a disturbed balance of neurotransmitters.

When levodopa is given alone, a large proportion of it does not reach the brain, because it is rapidly converted to dopamine by aromatic acid decarboxylase at extracerebral sites. Large doses must therefore be given in order to allow for sufficient levodopa to reach the brain and provide the dopamine needed to correct the deficiency observed in patients with Parkinson’s disease. These large doses of levodopa result in a sharp increase in the levels of circulating dopamine and other dopa metabolites, and the excessive quantities of these substances in extracerebral tissues may explain in part some of the side effects of levodopa, such as nausea, vomiting and cardiac arrhythmias. The high incidence of these adverse effects requires a very slow titration of levodopa and may interfere with the administration of an effective drug dosage.

The decarboxylase inhibitor, benserazide, at the recommended therapeutic doses, does not cross the blood-brain barrier. Thus, administration of this agent makes it possible to inhibit the peripheral decarboxylation of levodopa without significantly affecting its metabolism in the brain.

In this way, the formation of circulating dopamine is minimized and the incidence of extracerebral side effects may thereby be reduced while at the same time permitting more levodopa to reach the brain. Combined therapy with levodopa and benserazide reduces the amount of levodopa required for optimum therapeutic benefit and permits an earlier response to therapy.

Nevertheless, combined therapy does not decrease the adverse reactions due to central effects of levodopa. In fact, dyskinesias and oscillations in performance occur at lower dosages of levodopa and earlier in treatment during combined therapy. Plasma levels of levodopa are markedly increased when the drug is given in combination with benserazide compared to those obtained after levodopa alone. There is also a reduction in the level of dopa metabolites when levodopa is combined with benserazide. Clinical trials have suggested that the combination of levodopa and benserazide in a 4 to 1 ratio is effective in reducing peripheral side effects and the amount of levodopa required for therapeutic improvement.

Pharmacokinetics

The pharmacokinetics of 14C-benserazide administered alone and in combination with levodopa has been studied in six patients with Parkinson’s disease. Three of these patients were administered 50 mg of the inhibitor by both intravenous and oral routes. Three additional patients received oral doses of 50 mg 14C-benserazide alone and also in combination with 200 mg of levodopa.

Comparison of the time-plasma concentration curves of total radioactivity in the patients receiving oral and intravenous 14C-benserazide indicated that between 66% and 74% of the administered dose was absorbed from the gastrointestinal tract. Peak plasma concentrations of radioactivity were detected one hour after oral administration in five of the six patients.

Elimination of the 14C-label was primarily by urinary excretion with 86% to 90% of an intravenous dose recovered in the urine while 53% to 64% of the oral dose was detected in the urine. The majority of the 14C radioisotope was accounted for in the urine within 48 hours after administration. Fecal recovery studies conducted over five to eight days accounted for the majority (approximately 30%) of the remainder of administered 14C-benserazide.

In still another experiment in man, where 14C-dopa had been administered either intravenously (0.1 mg/kg) or orally (3 mg/kg), the administration of benserazide (16 mg to 24 mg orally) enhanced the 14C dopa and 14C-methyldopa plasma concentrations 6 to 10 fold over those observed with the administration of 14C-dopa alone. Also, the 14C-phenolcarboxylic acid concentration was 1/5 to 1/10th that which was observed when 14C-dopa was administered alone.

Absorption

Levodopa is mainly absorbed from the upper regions of the small intestine. Maximum plasma concentrations of levodopa are reached approximately one hour after ingestion of PROLOPA (levodopa and benserazide combination). The bioavailability of levodopa from PROLOPA is 98% (range 74-112%).

Food intake impairs or reduces the rate and extent of levodopa absorption. The peak levodopa plasma concentration is 30% lower and occurs later when PROLOPA is administered after a standard meal. The extent of levodopa absorption is reduced by 15% due to an increase in gastric emptying time.

Distribution

Levodopa crosses the blood-brain barrier by a saturable transport system. It is not bound to plasma proteins, and its volume of distribution is 57 litres. In contrast to levodopa, benserazide does not penetrate the blood-brain barrier at therapeutic doses. It is concentrated mainly in the kidneys, lungs, small intestine and liver.

Metabolism

Levodopa is metabolized by two major pathways (decarboxylation and O-methylation) and two minor ones (transamination and oxidation).

Aromatic amino acid decarboxylase converts levodopa to dopamine. The major end-products of this pathway are homovanillic acid and dihydroxyphenylacetic acid.

Catechol-O-methyltransferase methylates levodopa to 3-O-methyldopa. This major plasma metabolite has an elimination half-life of 15 hours and accumulates in patients who are treated with therapeutic doses of PROLOPA.

Decreased peripheral decarboxylation of levodopa when it is administered with benserazide is reflected in higher plasma levels of levodopa and 3-O-methyldopa and lower plasma levels of catecholamines (dopamine, noradrenaline) and phenolcarboxylic acids (homovanillic acid and dihydroxyphenylacetic acid).

Benserazide is hydroxylated to trihydroxybenzylhydrazine in the intestinal mucosa and the liver. This metabolite is a potent inhibitor of the aromatic amino acid decarboxylase.

Pyridoxine hydrochloride (Vitamin B6) accelerates the decarboxylation of levodopa and is therefore contraindicated in patients on levodopa alone.

Excretion

In the presence of peripherally inhibited levodopa decarboxylase, the elimination half-life of levodopa is approximately 1.5 hours. The elimination half-life is slightly longer in elderly patients with Parkinson’s disease. The clearance of levodopa in plasma is about 430 mL/min.

Benserazide is almost entirely eliminated by metabolism. The metabolites are mainly excreted in the urine (64%) and to a smaller extent in feces (24%).

Storage and Stability

Keep in a tightly closed, light-resistant container. Store at 15-30°C.

Dosage Forms, Composition and Packaging

Composition

Each PROLOPA 50-12.5 capsule contains 50 mg of levodopa and 12.5 mg of benserazide base in the form of benserazide hydrochloride.

Each PROLOPA 100-25 capsule contains 100 mg of levodopa and 25 mg of benserazide base in the form of benserazide hydrochloride.

Each PROLOPA 200-50 capsule contains 200 mg of levodopa and 50 mg of benserazide base in the form of benserazide hydrochloride.

Packaging

PROLOPA 50-12.5 capsules in bottles of 100: Light grey and blue capsules, size #4, with ROCHE imprinted in black ink on both the body and cap.

PROLOPA 100-25 capsules in bottles of 100: Blue and pale pink capsules, size #2, with ROCHE imprinted in black ink on both the body and cap.

PROLOPA 200-50 capsules in bottles of 100: Blue and caramel-coloured capsules, size #1, with ROCHE imprinted in black ink on both the body and cap.