Abstract

DRUG INDUCED PARKINSONISM: FOCUS ON EXTRAPYRAMIDAL SYMPTOMS AND CLINICAL INSIGHTS

*Dr. Alisha Naaz and Shifa Aashmeen

ABSTRACT

Drug-induced parkinsonism (DIP) is a secondary and often reversible form of Parkinsonism caused by medications that disrupt dopaminergic neurotransmission, primarily through D2 receptor blockade. The most common culprits include typical antipsychotics (e.g., haloperidol), atypical antipsychotics (though with lower risk), antiemetics (e.g., metoclopramide), and certain calcium channel blockers (e.g., cinnarizine). Typical antipsychotics pose the highest risk due to their high affinity and prolonged binding to D2 receptors, whereas atypical agents like quetiapine and clozapine are less likely to cause DIP due to their "fast-off" receptor kinetics. Epidemiologically, DIP accounts for approximately 20% of all Parkinsonism cases, with increased prevalence among elderly patients and women, likely due to age-related pharmacokinetic changes, polypharmacy, and greater susceptibility to extrapyramidal side effects. Clinically, DIP manifests with the classic triad of bradykinesia, rigidity, and tremor, often symmetrically, though asymmetry does not exclude the diagnosis. Symptoms typically develop within days to months after initiating the offending drug, with most cases appearing within the first three months. Diagnosis hinges on a thorough medication history and temporal correlation between drug exposure and symptom onset. Discontinuation of the causative agent usually leads to symptom resolution within weeks to months, supporting a DIP diagnosis. However, persistent or worsening symptoms beyond this period should raise suspicion for underlying idiopathic PD, which can be differentiated using dopamine transporter (DAT) imaging (showing reduced uptake in PD but normal in DIP) or cardiac MIBG scintigraphy (abnormal in PD). Treatment primarily involves withdrawing the offending drug or substituting it with a lower-risk alternative. In cases where discontinuation is not feasible, cautious use of anticholinergics or amantadine may be considered, though levodopa is generally ineffective. Early recognition and intervention are critical to prevent complications such as falls, functional decline, and unnecessary long-term antiparkinsonian therapy, underscoring the importance of medication review in at-risk populations.

Keywords: drug-induced parkinsonism, Parkinson's disease, pharmacotherapy, clinical manifestations, Parkinsonism.