ELDEPRYL^®

selegiline hydrochloride

Presentation

White or almost white round, convex, scored uncoated tablet with diameter of 6 ± 0.3 mm.

Uses

Actions

Selegiline is an irreversible inhibitor of monoamine oxidase (MAO), an intracellular enzyme associated with the outer membrane of mitochondria. Selegiline inhibits MAO by acting as a 'suicide' substrate for the enzyme: that is, it is converted by MAO to an active moiety that combines irreversibly with the active site of the enzyme and/or the enzyme's essential flavine adenine dinucleotide (FAD) co-factor. MAOs are currently subclassified into two types, A and B, which differ in their substrate specificity and tissue distribution. In humans, intestinal MAO is predominantly type-A, while most of that in the brain is type-B. At the recommended dose, selegiline has greater affinity with type-B than for type-A active sites and serves as a selective inhibitor of MAO type-B (MAO-B). However, this selectivity is dose-dependent and at higher doses (above 20mg/day), the selectivity of selegiline starts to diminish, resulting in increased inhibition of MAO-A . The precise dose at which selegiline becomes a non-selective inhibitor of all MAO is unknown.

In CNS neurones, MAO plays an important role in the catabolism of catecholamines (dopamine, noradrenaline and adrenaline) and serotonin. MAOs are also important in the catabolism of various exogenous amines found in a variety of foods and drugs. MAO in the gastrointestinal tract and liver (primarily type-A), for example, is thought to provide vital protection from exogenous amines (e.g. tyramine) that have the capacity, if absorbed intact, to cause a 'hypertensive crisis', the so-called 'cheese reaction'. This has been documented with non-selective MAO inhibitors (MAOIs).

It has been shown in several in vitro and in vivo experiments that selegiline does not potentiate the 'cheese reaction' effect. However, the pathophysiology of the 'cheese reaction' is complicated and is not fully understood. Selegiline's apparent freedom from this reaction may be due to selegiline's selective inhibition of MAO-B at clinically used doses (≤10mg/day) and selegiline's ability to prevent tyramine and other indirect acting sympathomimetics from displacing noradrenaline from adrenergic neurones (see Precautions).

The rate of MAO-B regeneration following discontinuation of selegiline treatment has not been quantitated. It is this rate, dependent upon de novo protein synthesis, which seems likely to determine how fast normal MAO-B activity can be restored.

Selegiline may have pharmacological effects unrelated to MAO-B inhibition. There is some evidence that it may increase dopaminergic activity by inhibiting dopamine reuptake at the synapse.

Effects resulting from selegiline administration may also be mediated through its metabolites. Three of its principal metabolites may have pharmacological actions of their own. L-amphetamine and l-methamphetamine interfere with neuronal uptake and enhance release of several neurotransmitters (e.g. noradrenaline, dopamine, serotonin). However, l-amphetamine and l-methamphetamine have significantly less activity than the corresponding d-isomer. In animal studies, the third metabolite, N-desmethylselegiline, appears to act as a selective inhibitor of MAO-B. The extent to which each of these metabolites contributes to the effects of selegiline is unknown.

Pharmacokinetics

General Characteristics

Selegiline is readily absorbed from the gastrointestinal tract. The maximal concentrations are reached in 0.5 hours after oral administration. The bioavailability is low - on average 9.4 ± 5.9% of unchanged selegiline from a 10mg oral dose reaches the systemic circulation. A substantial increase in selegiline bioavailability (up to threefold) occurs when selegiline is administered with food high in fat.

Selegiline is a lipophilic, slightly basic compound which quickly penetrates into tissues, including the brain. It is rapidly distributed throughout the body, with the apparent volume of distribution being 508±182 litres after an intravenous 10mg dose; selegiline is strongly bound to plasma proteins especially to macroglobulins and, to a lesser extent to albumin.

Selegiline is rapidly metabolised, mainly in the liver, into N-desmethylselegiline (the major metabolite), l-methamphetamine and l-amphetamine. In humans, these three metabolites have been identified in plasma and urine after single and multiple doses of selegiline. Following the oral administration of a single dose of 10mg selegiline hydrochloride, [for example, N-desmethylselegiline (mean t½ 2.0 hours); l-amphetamine (mean t_½ 17.7 hours); and l-methamphetamine (mean t½ 20.5 hours)], were found in serum and urine. Metabolites of selegiline are excreted mainly via the urine, with about 15% occurring in the faeces. Over a period of 48 hours, urinary excretion of these metabolites accounted for 45% of the dose administered. The mean elimination half-life of an intravenous 10mg dose of selegiline is 1.6±-0.3 hours. The total body clearance of selegiline is about 240L/hour. The half life of an oral 10mg dose of selegiline is 1.2-1.8 hours.

Characteristics in Patients

Selegiline is metabolised quickly, but, due to irreversible MAO-B inhibition, the duration of clinical effect does not depend on the elimination time of selegiline, and therefore once daily dosing can be applied.

No information is available yet concerning polymorphic metabolism or effect of renal or hepatic insufficiency to the metabolism of selegiline.

Clinical Trials

Selegiline as Monotherapy in the Early Phase of Parkinson's Disease

Four randomised, double-blind, placebo-controlled, parallel group studies, involving 501 patients treated with selegiline and 498 patients treated with placebo, have been conducted to end 1994 where the primary outcome measure was time to initiation of levodopa. The largest trial, the DATATOP study, randomised 800 patients to 4 different treatment regimens. These regimens were: selegiline (10mg once daily); vitamin E; a combination of selegiline with vitamin E; and placebo. The primary outcome measure was time to requirement for levodopa as additional therapy. An analysis of the primary endpoint after 12 months into the trial showed that, of those patients who were treated with selegiline, 97/399 (24.3%) had progressed to the point of requiring additional therapy (levodopa). Of those patients who had received vitamin E or placebo, 176/401 (43.9%) required the addition of levodopa. The results demonstrated that selegiline delayed onset of the stage where levodopa was required, the delay in commencement of levodopa being approximately 7-9 months in the particular group studied. Overall, selegiline was shown in these four studies to significantly delay the need to introduce levodopa by 5-9 months, compared to the placebo group. Evidence was less clear as to whether selegiline exerted a symptomatic effect.

Selegiline as Adjunctive Therapy in the Early and Middle Phases of Parkinson's Disease

Six randomised, double-blind, placebo-controlled, parallel or cross-over studies, involving 157 patients treated with selegiline in combination with levodopa and 157 patients treated with placebo in combination with levodopa have been conducted in patients in the early and middle phases of Parkinson's disease to end 1995. When levodopa was added to selegiline therapy, or both drugs were given together, to de novo patients with Parkinson's disease, optimal clinical conditions, in terms of disability, was maintained with levodopa doses 50-80% lower than if selegiline was not co-administered. Increases in daily levodopa dosage were significantly smaller in the selegiline+levodopa group, compared to the placebo+levodopa group, over time (up to 5 years). Levodopa dosing frequency was significantly in favour of patients on selegiline+levodopa compared to those on placebo+levodopa (i.e. less levodopa doses/day in the former group). Additionally, patients treated with selegiline+levodopa had attenuated deterioration in their disability scores, compared to the placebo+levodopa group.

The conclusions from these studies were that the need to increase levodopa dose was slowed down.

For information on the adverse events reported in the clinical trials, refer to the section on Adverse Effects, below.

Indications

ELDEPRYL is indicated for the treatment of patients with Parkinson's disease. It can be used as monotherapy in the early phases of the disease and as adjunctive therapy with levodopa (with/without a peripheral decarboxylase inhibitor).

Dosage and Administration

Selegiline is administered as monotherapy in the early phase of the disease, or as adjunctive therapy with levodopa (with/without a peripheral decarboxylase inhibitor). In each case the initial dose is 5 mg in the morning. The dose is usually raised up to 10 mg in the morning or two divided doses of 5 mg taken at breakfast and lunch. There is no evidence that additional benefit will be obtained from the administration of higher doses.

After two to three days of adjunctive therapy, an attempt may be made to reduce the dose of levodopa (10-30%) if levodopa-related adverse reactions occur. Further reductions of levodopa may be possible during continued selegiline therapy.

Double-blind studies on early-phase parkinsonian patients showed that patients receiving selegiline monotherapy manage significantly longer without levodopa therapy than controls receiving placebo. These patients could also maintain their ability to work longer.

After the initiation of levodopa therapy, selegiline potentiates and extends the effect of levodopa, and thus a reduction of levodopa dosage is possible. By adding selegiline to levodopa therapy the fluctuations in disability, e.g. end-of-dose type fluctuations, can be reduced.

Contraindications

Known hypersensitivity to selegiline.

Pethidine

Pethidine is contraindicated in combination with MAOIs because of reports of serious, sometimes fatal, reactions in patients receiving this combination and in patients who have discontinued MAOI therapy and are then started on pethidine within two weeks of discontinuation. (This warning is often extended to other opioids). Agitation, delirium, irritability, hyperpyrexia, restlessness, rigidity, stupor and sweating have been reported with the concomitant use of pethidine and selegiline. The mechanism of action is not fully understood.

Selective Serotonin Reuptake Inhibitors (SSRIs)

There have been reports of serious, sometimes fatal, reactions in patients receiving SSRIs in combination with selegiline and in patients who have recently discontinued SSRIs and are then started on a MAOI. Agitation, ataxia, cold sweats, hypertension, mania, pseudophaecochromocytoma, 'serotonergic reaction' and shivers have been reported with the concomitant use of selegiline and SSRIs.

Since the mechanisms of these reactions is also not fully understood, it is recommended to avoid the combination of selegiline and SSRIs.

At least five weeks should be allowed between discontinuation of, for example, fluoxetine, sertraline or paroxetine and initiation of selegiline therapy, due to the long t_½ of these SSRI drugs and/or their active metabolites. A two-week period between selegiline discontinuation and SSRI initiation would be sufficient, because of the short t_½ of selegiline and its active metabolites.

Warnings and Precautions

The recommended dose of 10mg/day should not be exceeded because of the risks associated with non-selective inhibition of MAO i.e. 'cheese reactions' (see Pharmacology). In higher doses (> 20mg/day), the selectivity of selegiline starts to diminish, resulting in increased inhibition of MAO-A. The possibility of a hypertensive reaction at higher doses (>20mg/day) of selegiline after ingestion of food or drugs rich in various exogenous amines has to be taken into account. Even at the recommended dose of 10mg/day the selectivity of selegiline for MAO-B may not be absolute. The precise dose at which selegiline becomes a non-selective inhibitor of all MAO is unknown.

Some patients on adjunctive therapy may experience exacerbation of levodopa-associated side effects, presumably due to the increased amounts of dopamine reacting with super-sensitive post synaptic receptors. These effects may often be mitigated by reducing the dose of levodopa by approximately 10-30%.

Selegiline should be given cautiously to patients with peptic or duodenal ulcer, labile hypertension, cardiac arrhythmias, severe angina pectoris or psychosis as selegiline may exacerbate these conditions.

Transient increases in liver transaminases have been reported during selegiline treatment (see Adverse Effects).

Adverse Effects

In monotherapy, selegiline has been found to be well tolerated. Dry mouth, transient rise of serum alanine aminotransferase values and sleeping disorders have been reported more frequently than in patients receiving placebo. Because selegiline potentiates the clinical efficacy of levodopa, the adverse reactions of levodopa, e.g. abnormal movements, nausea, agitation, confusion, hallucinations, headache, postural hypotension, cardiac arrhythmias and vertigo, may worsen when selegiline is added to the maximum tolerated levodopa dose. Micturition difficulties and skin reactions have also been reported during selegiline treatment. Follow-up of these possible adverse reactions is important.

Clinical Trials

The table below summarises the adverse events reported in patients enrolled in double-blind, placebo-controlled trials where selegiline had been used as monotherapy or as adjunctive therapy with levodopa. Included are all adverse events which occurred with an incidence of 1% or greater in any treatment group. An asterisk represents an incidence of <1% for that treatment group; - indicates that the adverse event was not reported.

Table 1: Percentage of Adverse Events (occurring with an incidence ≥ 1%)

Reported from Double-Blind, Placebo-Controlled Trials using Selegiline Monotherapy or Adjunctive Therapy (with Levodopa), in Parkinson's Disease - to end 1995

an asterisk represents an incidence of <1%
- indicates that the adverse event was not reported

Selegiline and Mortality

In 1995, the UK Parkinson's Disease Research Group (PDRG) reported in a 5.6 year interim analysis of the long-term prospective study an increased overall mortality in the patient group randomised to receive selegiline and levodopa, when compared to those treated with levodopa only (Lees et al. 1995). This study has been the subject of considerable debate and criticism in the medical literature because of significant design and clinical research practice issues (Olanow et al. 1996; Gerlach et al. 1996; Breteler, 1998). A further 21 months update (mean 6.8 year) on the study including all mortality information to the end of September 1995 was published in 1998 (Ben Shlomo et al).

During 1996-1997, the British Medicines Control Agency (MCA) sponsored a study evaluating mortality among patients with Parkinson's disease on various treatments using data from their General Practice Research Database. This study, combined with the MCA's review of all available evidence from trials and observational studies, did not confirm the increased mortality risk in users of selegiline in combination with levodopa which was seen in the PDRG study (Evans and Sivananthan 1997).

No other clinical trial to date has shown an increase in mortality associated with the use of selegiline. (Birkmayer 1985; Caraceni 1996; Shoulson 1996; Di Rocco 1996; Fuell 1997; Thorogood 1998; (US) Parkinsons Study Group 1998. The need for a formal systematic review of all relevant trial data to assess survival, disability and the risk of dementia has been identified (Counsell, 1998)

Post-Marketing Surveillance Data

Information in the manufacturer's database on adverse events (post-marketing surveillance data) has allowed the assignment of levels of causality in an estimated population of >300,000 patients. Adverse events experienced by patients on monotherapy or adjunctive therapy from spontaneous reports have not been separated.

The estimated frequency of adverse events, for a body system, are listed below; frequency has been grouped according to the following criteria:

* Uncommon: > 0.1% and < 1%; * Rare: > 0.01% and < 0.1%; * Very rare: < 0.01%.

As under-reporting occurs with spontaneous voluntary reporting systems, the estimated frequency may or may not be an accurate reflection of clinical experience.

Uncommon

Psychiatric Disorders

aggressive reaction, agitation, anxiety, confusion, delirium, depression, hallucination, insomnia, libido - increased, manic reaction, nervousness, paranoid reaction, paroniria, psychosis, sleep disorder, somnolence, thinking - abnormal

Rare

Autonomic Nervous System Disorders

dry mouth, flushing, sweating - increased, syncope

Body (as a whole) Disorders

asthenia, death, fatigue, fever, headache, malaise, oedema, pain

Cardio- and Vascular System Disorders

angina pectoris, arrhythmia, cerebrovascular disorder, hypertension, hypotension, postural hypotension, myocardial infarction, palpitation, tachycardia

Central Nervous System Disorders

ataxia, coma, confusion, convulsions, dizziness, dyskinesia, gait - abnormal, hypertonia, muscle contractions - involuntary, speech disorder, tremor, vertigo

Gastro-intestinal System Disorders

abdominal pain, anorexia, constipation, diarrhoea, dyspepsia, nausea, vomiting

Skin and Appendages Disorders

alopecia, photosensitivity reaction, pruritis, rash

Very Rare

Hæmatological Disorders

white cell disorder, thrombocytopenia

Liver and Biliary System Disorders

hepatic enzymes increased

Metabolic and Nutritional Disorders

hyperglycæmia, hypoglycæmia

Musculo-skeletal System Disorders

muscle weakness, Neuroleptic Malignant Syndrome

Reproductive Disorders

sexual dysfunction

Respiratory System Disorders

dyspnoea

Special Senses Disorders

taste perversion, tinnitus, vision - abnormal

Urinary System Disorders

incontinence, micturition frequency

Interactions

Moclobemide

No tolerability problems have been reported when selegiline and moclobemide, a reversible inhibitor of MAO-A, have been used in combination. However, when used together, the exogenous amine sensitivity factor may increase. A diet low in exogenous amines such as tyramine is recommended for patients taking the combination.

Non-selective, Irreversible MAOIs

Combined use with selegiline may cause severe hypotension.

Pethidine

See Contridications.

Serotonergic Drugs

Treatment with heterogeneous serotonergic drugs in patients primarily with psychiatric illness taken alone or in combination with other drugs such as MAOIs has been uncommonly associated with symptoms of, myoclonus, tremor, confusion, restlessness, ataxia and hyperreflexia (see Clinical Trials ). While usually short-lived, it can lead to intensive care admissions and is potentially fatal. The occurrence of the serotonin syndrome may occur after use of SSRIs, TCAs, tetracyclic antidepressants, 3-4-methylenedioxy-metamphetamine (MDMA or ecstasy) and other 5-HT potentiating agents and the antipsychotic drug, clozapine. The treatment of choice is cessation of the drugs responsible. Treatment with 5-HT receptor antagonists cyproheptadine, methysergide and propranolol may shorten the syndrome duration.

SSRIs

See Contraindications.

Tricylic Antidepressants

Severe CNS toxicity has been reported in patients when a combination of tricyclic antidepressants and selegiline have been used. In one patient receiving amitriptyline and selegiline this included hyperpyrexia and death; another patient receiving protriptyline and selegiline experienced tremor, agitation and restlessness, followed by unresponsiveness and death two weeks after selegiline was added. Other adverse reactions occasionally reported in patients receiving a combination of selegiline with various tricyclic antidepressants include hyper/hypotension, dizziness, diaphoresis, tremor, seizures and changes in behavioural and mental status. Since the mechanisms of these reactions are not fully understood, it is recommended to avoid concomitant use of selegiline together with tricyclic antidepressants.

At least two weeks should be allowed between discontinuation of a tricyclic antidepressant and initiation of selegiline therapy, due to the long t_½ of some tricyclics and their active metabolite(s). A two-week period between selegiline discontinuation and tricyclic antidepressant initiation would be sufficient, because of the short t_½ of selegiline and its active metabolites.

Other

No other clinically relevant interactions have been attributed to the combined use of selegiline and other drugs. However, potential interactions have not been fully investigated.

During selegiline treatment, the possibility of a hypertensive reaction as a result of an interaction with indirect sympathomimetic drugs has to be taken into account. Foods containing various exogenous amines such as tyramine have not been reported to induce hypertensive reactions during selegiline treatment at doses used in the treatment of Parkinson's disease.

Carcinogenesis, Mutagenesis and Impairment of Fertility

Selegiline showed no evidence of carcinogenicity in a 78-week study in mice at dietary levels up to 30 mg/kg/day and a 104-week study in rats at dietary levels up to 17.5 mg/kg/day.

Selegiline did not induce gene mutations in Salmonella typhimurium or chromosomal damage in an in vivo chromosomal aberration assay. No definitive mammalian gene mutation assay has been performed.

Selegiline did not impair fertility in rats at oral doses up to 100 mg/kg/day.

Use in Pregnancy

Pregnancy Category B2.

(Category B2. Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human foetus having been observed. Studies in animals are inadequate or may be lacking, but available data show no evidence of an increased occurrence of foetal damage.).

Insufficient animal reproduction studies have been performed to conclude that selegiline poses no teratogenic risk. However, one rat study carried out at doses of up to 30 mg/kg/day revealed no evidence of a teratogenic effect.

The effects of selegiline in human pregnancy are unknown. The available safety data concerning the use of selegiline during pregnancy is insufficient to justify use in this patient group. Therefore, selegiline should not be given to pregnant women unless the expected benefit clearly outweighs any potential risk.

Use in Lactation

It is not known whether selegiline is excreted in human milk. The available safety data concerning the use during lactation is insufficient to justify the use of selegiline in this patient group.

Paediatric Use

The effects of selegiline in children have not been evaluated.

Overdosage

No overdosage cases are known. However, experience gained during selegiline's development reveal that some individuals exposed to doses of 600 mg/day selegiline suffered severe hypotension and psychomotor agitation.

Theoretically, overdosage causes significant inhibition of both MAO-A and MAO-B and thus, symptoms may resemble those observed with non-selective MAOIs, particularly disorders of the central nervous and cardiovascular systems (e.g. drowsiness, dizziness, faintness, irritability, hypotension, hyperactivity, agitation, severe headache, hallucination, hypertension, hypotension, vascular collapse, rapid and irregular pulse, precordial pain, respiratory depression and failure, hyperpyrexia, diaphoresis). There is no specific antidote and the treatment is symptomatic.

Pharmaceutical Precautions

Store below 25°C or 77°F.

Package Quantities

Tablets - 5 mg selegiline hydrochloride; 100 tablets/bottle.

Further Information

Seliginine hydrochloride is a white to near-white crystalline powder, freely soluble in water, chloroform and methanol and has a molecular weight of 223.75. It is a laevorotatory acetylenic derivative of phenethylamine, also known as L-deprenyl. Its chemical name is (R)-methyl a-methylphenylethyl)prop-2-ynlamine hydrochloride. Cas No.: 2079-54-1

Other ingredients of the tablet are: maize starch, microcrystalline cellulose, mannitol, povidone and magnesium stearate.

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