The use and potential abuse of anticholinergic antiparkinson drugs in Norway: a pharmacoepidemiological study.

Anticholinergic antiparkinson drugs are used to ameliorate extrapyramidal symptoms caused by either Parkinson's disease or antipsychotic drugs, but their use in the treatment of Parkinson's disease is assumed to be in decline. Patients with psychotic conditions have a high prevalence of abuse of drugs, including anticholinergic antiparkinson drugs. Anticholinergic antiparkinson drugs in Norway were primarily prescribed to patients using antipsychotic medication. The risk of abuse of this group of drugs was small, even among patients who probably abused other drugs. The use of anticholinergic antiparkinson drugs is assumed to have shifted from the therapy of Parkinson's disease to the amelioration of extrapyramidal adverse effects induced by antipsychotic drugs. There is a considerable body of data suggesting that anticholinergic antiparkinson drugs have a potential for abuse. The aim was to investigate the use and potential abuse of this class of drugs in Norway. Data were drawn from the Norwegian Prescription Database on sales to a total of 73 964 patients in 2004 of biperiden and orphenadrine, and use in patients with Parkinson's disease or in patients who were also prescribed antipsychotic agents. Possible abuse of these drugs was assessed by the level of use, skewedness of use, indications of drug-seeking behaviour and concomitant use of benzodiazepine tranquillizers, a group of prescription drugs with a recognized potential for abuse. Anticholinergic antiparkinson drugs were prescribed to 4.5% of all outpatients who used antipsychotic drugs. This outnumbered sales to patients with Parkinson's disease by >20 to 1. We found indications of abuse of benzodiazepine tranquillizers among patients using antipsychotics, but there were no clear indications of abuse of anticholinergics, even among patients who were strongly suspected of abuse of benzodiazepines. Anticholinergic antiparkinson drugs were used primarily by patients with psychotic illnesses. These patients have a very high prevalence of legal and illegal drug abuse, but the risk of abuse of anticholinergic antiparkinson drugs seemed small.