Association between the use of anticholinergic antiparkinson drugs and safety and receptor drug-binding profiles of antipsychotic agents.

PURPOSE: The use of anticholinergic antiparkinson drugs is almost exclusively confined to treating antipsychotic-induced extrapyramidal side effects (EPS). We investigated the prevalence of concomitant prescription of anticholinergics as a proxy for antipsychotic-induced EPS and compared variance in prevalence with differences in the assumed mechanisms of action of antipsychotics on central nervous system (CNS) transmitter systems (i.e., receptor drug-binding profiles). We paid special attention to potential differences between typical and atypical antipsychotics.
METHODS: Data were drawn from the Norwegian Prescription Database on sales of antipsychotic and anticholinergic antiparkinson drugs to a total of 57,130 outpatients in 2004. We assessed concomitant dispensations of antipsychotic and anticholinergic drugs and correlated the prevalence of concomitantly prescribed anticholinergics to previously assessed receptor-binding profiles of antipsychotics.
RESULTS: The concurrent use of anticholinergics varied between 0.4% and 26.0% for patients using a single antipsychotic agent. The prevalence of anticholinergic comedication was more than twice as high in patients using two or more antipsychotic drugs. Four typical antipsychotics (fluphenazine, zuclopenthixol, haloperidol, and perphenazine) were associated with higher concomitant use of anticholinergics than the rest. For the remaining 14 antipsychotic agents, the difference between typical and atypical antipsychotics was neither pronounced nor systematic. A high degree of D2-receptor antagonism and a high 5-HT2A/D2-receptor-affinity ratio coincided with the use of anticholinergics.
CONCLUSIONS: The liability of antipsychotic drugs to cause EPS seemed to vary considerably and largely independently of the distinction between typical and atypical antipsychotics.