Antipsychotic drug exposure may have neurologic consequences

By Eleanor McDermid, Senior medwireNews Reporter

French researchers report an increased risk for Parkinson's disease (PD) in elderly people who have past exposure to neuroleptic drugs.

"Although the mechanisms underlying this relation need further exploration, our findings plead for a limitation of the use of these drugs in elderly people," Alexandra Foubert-Samier (University Bordeaux Segalen) and team write in Neurology.

They believe that about one in five cases of PD could be avoided by restricting use of antipsychotics. Most patients in their study received the drugs for nonpsychiatric indications, including insomnia, anxiety, vertigo, and gastrointestinal problems, despite such use being discouraged.

However, the researchers note that these patients all received first-generation antipsychotics, which were in use at the time of the study. "It is not known whether the same risk would persist for the new generation of atypical antipsychotics."

The 2991 study participants were drawn at random from electoral lists, and were all older than 75 years and not institutionalized, which the team says may explain why most neuroleptic drug use in this cohort was for nonpsychiatric purposes.

During 15 years of follow up, 117 participants developed parkinsonism, with 43 of these having probable PD. Of these, 22.2% and 32.6%, respectively, had previous exposure to neuroleptic drugs, compared with just 16.6% of participants who did not develop parkinsonism.

After accounting for gender and previous occupation, neuroleptic exposure raised the risk for parkinsonism 1.65-fold and the risk for probable PD 3.16-fold, and this association was present for benzamides and phenothiazines considered separately. The population-attributable fraction of probable PD was 21.7% for all neuroleptics, 8.2% for benzamides, and 12.2% for phenothiazines.

Foubert-Samier et al note that neuroleptic use may expose, rather than cause, parkinsonism, but they also point out that only 30% of the patients in their study who developed PD after drug exposure had symptoms of parkinsonism at the time of the exposure.

The researchers also observe that insomnia and anxiety can be early manifestations of PD, which could have triggered prescription of neuroleptics in patients already destined to develop PD. But when they looked at past use of benzodiazepines, which are often prescribed for these conditions, they found no association with PD.

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