Caution urged when substituting olanzapine for clozapine in
Parkinson's patients
WESTPORT, Oct 19 (Reuters) - Clinicians are urged to exercise caution
when switching Parkinson's disease patients from clozapine to
olanzapine, according to a paper that appears in the September/October
issue of Clinical Neuropharmacology.
Nine of 12 Parkinson's patients who were psychiatrically stable on
clozapine experienced worsening Parkinson's symptoms when they were
switched to olanzapine "...and were unable to make the transition," Dr.
Joseph H. Friedman of Memorial Hospital of Rhode Island, in Pawtucket,
and others report.
The patients, with a mean age of 69 years and mean duration of
Parkinson's of 12.2 years, generally received increasing doses of
olanzapine in 2.5 mg increments as the clozapine was reduced 12.5 mg
each week.
It is possible that patients' Parkinson's symptoms worsened as a result
of an "...anticholinergic rebound effect..." that has been observed in
schizophrenics after clozapine withdrawal, the investigators suggest.
Alternatively, the combination of clozapine and olanzapine during the
transition may be harmful. "It is conceivable that the lingering effects
of clozapine acted synergistically with the olanzapine to cause worsened
parkinsonism or other problems that indirectly worsened outcome," Dr.
Friedman and colleagues write.
They conclude that "[s]witching frail but otherwise stable [Parkinson's
disease] patients from clozapine to olanzapine may be unwise."
Clin Neuropharmacol 1998;21:285-288.
--
Judith Richards, London, Ontario, Canada
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