• Suspect drug-induced parkinsonism if symptoms appear whilst the person is taking a drug known to induce parkinsonism. In the case of antipsychotics, symptoms usually appear within 10 weeks of starting the drug.
• Other features of drug-induced parkinsonism include:
• Motor symptoms that are rapid in onset and bilateral (as opposed to starting slowly and being unilateral, as in early Parkinson's disease).
• Absence of rigidity.
• Absence of rest tremor, or the presence of an action tremor (postural and kinetic).
• In people taking an antipsychotic, the presence of akathisia (restlessness of arms and legs) and dystonia (abnormal movements and postures caused by involuntary spasms).
• However, it is often not possible to distinguish drug-induced parkinsonian from Parkinson's disease on the basis of signs and symptoms.
• Many clinical features of drug-induced parkinsonism are similar to those of Parkinson's disease, including akinesia and bradykinesia, masked face, reduced blinking, postural instability, flexed posture, reduced arm-swing when walking, and a shuffling gait with hurrying small steps (festinating).
• If drug-induced parkinsonism is suspected, reduce or stop the drug (if possible) and refer to a specialist.
• Do not delay referral to assess the response.

In depth