Typical Antipsychotics — EPS & Adverse Effects

A patient on haloperidol develops a rigid jaw and arched back within hours of the first dose. Recognizing which EPS this is — and how fast you act — determines whether the airway stays open.

Typical (first-generation) antipsychotics like haloperidol, chlorpromazine, and fluphenazine work by blocking dopamine D2 receptors in the mesolimbic pathway to reduce positive psychotic symptoms (hallucinations, delusions). Because D2 blockade is non-selective, it also hits the nigrostriatal pathway, producing extrapyramidal symptoms (EPS) — the signature adverse effect of this drug class. EPS follow a predictable timeline: acute dystonia appears hours to days after initiation (muscle spasms of the neck, jaw, tongue, eyes — treat emergently with benztropine or diphenhydramine IM/IV). Akathisia (restless inability to sit still) emerges within days to weeks. Parkinsonism (bradykinesia, shuffling gait, cogwheel rigidity, mask-like face) develops over weeks. Tardive dyskinesia (TD) — involuntary lip-smacking, tongue movements, facial grimacing — appears after months to years of use and may be irreversible, making early detection critical. High-potency agents (haloperidol, fluphenazine) carry greater EPS risk; low-potency agents (chlorpromazine) cause more sedation and anticholinergic effects instead. Monitor with the Abnormal Involuntary Movement Scale (AIMS) at baseline and regularly to catch TD early.

Key Distinctions

Don't confuse akathisia (inner restlessness, pacing) with psychotic agitation — medicating akathisia with more antipsychotic worsens it. Students mix up acute dystonia (hours, treat with anticholinergic) and tardive dyskinesia (months-years, discontinue or switch the offending agent — anticholinergics don't help and can worsen TD). Neuroleptic malignant syndrome (NMS) is NOT EPS — it's a life-threatening emergency with hyperthermia, lead-pipe rigidity, and elevated CK requiring dantrolene.

Clinical Pearl

EPS timeline mnemonic: hours → Dystonia, days → Akathisia, weeks → Parkinsonism, months → Tardive dyskinesia. Think "DAPT" — the faster it appears, the faster you treat.