Drug-induced parkinsonism (DIP), also known as iatrogenic parkinsonism or medication-induced parkinsonism, is a movement disorder caused by exposure to dopamine-blocking medications, resulting in parkinsonian symptoms such as tremor, rigidity, bradykinesia, and postural instability. It accounts for approximately 10-20% of all parkinsonism cases and is one of the most common causes of secondary parkinsonism[1][2].
DIP was first recognized in the 1950s shortly after the introduction of antipsychotic medications (chlorpromazine). The condition is considered a form of nigrostriatal dopaminergic denervation caused by pharmacological blockade of dopamine D2 receptors in the basal ganglia[3].
Antipsychotics (most common cause):
| Drug | Relative Risk | Notes |
|---|---|---|
| Haloperidol | High | First-generation, potent D2 blocker |
| Fluphenazine | High | Typical antipsychotic |
| Risperidone | Moderate-High | Atypical with D2 blockade |
| Olanzapine | Moderate | Atypical |
| Quetiapine | Low | Milder D2 blockade |
| Clozapine | Very Low | Exception - used to treat PD psychosis |
Antiemetics:
Other dopamine antagonists:
DIP results from pharmacological blockade of dopamine D2 receptors in the nigrostriatal pathway[4]:
The condition represents a functional blockade rather than structural degeneration, which explains the potential for reversibility after drug withdrawal.
| Feature | Drug-Induced Parkinsonism | Parkinson's Disease |
|---|---|---|
| Onset | Symmetric (bilateral from start) | Usually unilateral |
| Progression | Rapid (weeks-months) | Slow (years) |
| Temporal relation | Within months of drug start | Idiopathic |
| Tremor | Less prominent | Classic resting tremor |
| Postural instability | Early | Late |
| Levodopa response | Poor | Good initially |
| Time to resolution | Weeks to months after withdrawal | N/A - progressive |
History:
Neurological examination:
Differential diagnosis:
This can help differentiate DIP from degenerative parkinsonian disorders[5].
The most important intervention is discontinuing the offending agent:
If symptoms persist after withdrawal:
| Treatment | Response | Notes |
|---|---|---|
| Levodopa/Carbidopa | Variable | Often limited response |
| Dopamine agonists | Variable | May help some patients |
| Amantadine | Often effective | Also treats akathisia |
| Anticholinergics | Limited | Trihexyphenidyl, benztropine |
If medication cannot be discontinued:
Co-existing tardive dyskinesia:
Van Gerpen JA. Drug-induced parkinsonism. In: Pfeiffer RF, Wszolek ZK, Ebholt M, eds. Parkinson's Disease. CRC Press; 2012:331-344. 2012. ↩︎
Fitzgerald PM. Drug-induced parkinsonism. In: Jankovic J, Tolosa E, eds. Parkinson's Disease and Movement Disorders. 5th ed. Lippincott Williams & Wilkins; 2007:301-310. 2007. ↩︎
Delay J, Deniker P. Drug-induced extrapyramidal syndromes. In: Vinken PJ, Bruyn GW, eds. Handbook of Clinical Neurology. Vol 6. North-Holland Publishing; 1968:248-266. 1968. ↩︎
Klawans HL, Tanner CM. Drug-induced parkinsonism. In: Calne DB, ed. Parkinsonism and Related Disorders. Elsevier; 1986:59-72. 1986. ↩︎
Lorberboym M, et al. Dopamine transporter imaging and I-123-ioflupane (DaTscan) in drug-induced parkinsonism. J Neurol Sci. 2016;371:137-141. 2016. ↩︎