Drug-induced Extrapyramidal Symptoms
Drug-induced extrapyramidal symptoms (EPS) are involuntary movement problems that arise as side effects of certain medicines, most commonly antipsychotics, antiemetics, and some older antidepressants. They are widely encountered wherever these medicines are used, and they are manageable once recognised.
Key points
- Antipsychotics, antiemetics and some older antidepressants are the medicines most commonly responsible for these involuntary movement effects.
- Presentations range from sudden muscle spasms in the neck or jaw to tremor, restlessness, or repetitive face and limb movements after long-term use.
- Procyclidine and trihexyphenidyl ease rigidity and tremor by blocking overactive brain receptors linked to disrupted dopamine signalling.
- Akathisia and tardive dyskinesia often call for a different approach and specialist input rather than the standard anticholinergic add-on.
What EPS looks like and how it is treated
EPS covers several distinct patterns. Acute dystonia brings sudden, sustained muscle contractions, often in the neck or jaw. Parkinsonism produces tremor, slow movement, and muscle stiffness. Akathisia is an intense inner restlessness that compels constant movement. Tardive dyskinesia, which can develop after long-term use, involves repetitive, involuntary movements of the face and limbs.
The standard approach is to reduce the triggering medicine if possible, then add an anticholinergic agent to counteract the movement effects. Agents in the neurology category such as procyclidine and trihexyphenidyl block the muscarinic receptors in the brain that become overactive when dopamine pathways are disrupted, relieving rigidity, tremor, and dystonia. Akathisia and tardive dyskinesia may need different strategies and specialist input.
If EPS symptoms appear suddenly, especially difficulty swallowing or breathing during an acute dystonic reaction, seek medical attention promptly.