MAO-B Inhibitor

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Chapter: Essential pharmacology : Antiparkinsonian Drugs

Selegiline (Deprenyl) : It is a selective and irreversible MAOB inhibitor. Two isoenzyme forms of MAO, termed MAOA and MAOB are recognized; both are present in peripheral adrenergic structures and intestinal mucosa, while the latter predominates in the brain and blood platelets.


MAO-B INHIBITOR

 

Selegiline (Deprenyl)

 

It is a selective and irreversible MAOB inhibitor. Two isoenzyme forms of MAO, termed MAOA and MAOB are recognized; both are present in peripheral adrenergic structures and intestinal mucosa, while the latter predominates in the brain and blood platelets. Unlike nonselective MAO inhibitors, selegiline in low doses (10 mg/day) does not interfere with peripheral metabolism of dietary amines; CA accumulation and hypertensive reaction does not develop, while intracerebral degradation of DA is retarded. This is responsible for the therapeutic effect in parkinsonism. Higher doses can produce hypertensive interactions.

 

Selegiline alone has mild antiparkinsonian action in early cases. Administered with levodopa, it prolongs levodopa action, attenuates motor fluctuations and decreases ‘wearing off’ effect. As an adjuvant to levodopa, it is beneficial in 50–70% patients and permits 20–30% reduction in levodopa dose. However, advanced cases with ‘on-off’ effect are not improved and the peak dose levodopa side effects such as dyskinesias, mental confusion or hallucinations may be worsened. Moreover, clinical benefits derived from selegiline are short lived (6–26 months).

 

Based on the hypothesis that oxidation of DA and/or environmental toxins (MPTP-like) in the striatum by MAO to free radicals was causative in parkinsonism, it was proposed that early therapy with selegiline might delay progression of the disorder. However, no difference in the course of the disease has been detected on follow up of selegiline treated patients in large multicentric studies.

 

Adverse Effects

 

Postural hypotension, nausea, confusion, accentuation of levodopa induced involuntary movements and psychosis.

Contraindicated in patients with convulsive disorders.

 

Selegeline interacts with pethidine causing excitement, rigidity, hyperthermia, respiratory depression. It may also interact with tricyclic antidepressants and selective serotonin reuptake inhibitors.

 

ELDEPRYL 5, 10 mg tab; SELERIN, SELGIN 5 mg tab; Dose: 5 mg with breakfast and with lunch, either alone (in early cases) or with levodopa/carbidopa. Reduce by 1/4th levodopa dose after 2–3 days of adding selegiline.

 

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