MAO-B Inhibitor
| Home | | Pharmacology |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.
