Side effect	Features	Time of maximal risk	Proposed mechanism	Treatment
Acute dystonia	Muscle spasms of the tongue, face, neck, and back; may mimic seizures; not hysteria	One to five days	Unknown	Antiparkinsonian agents are diagnostic and curative*
Akathisia	Motor restlessness; not anxiety or agitation	Five to 60 days	Unknown	Reduce dose or change drug; antiparkinsonian agents (benzodiazepines or propranolol [Inderal])† may help
Parkinsonism	Bradykinesia, rigidity, variable tremor, mask facies, shuffling gait	Five to 30 days (can recur even after a single dose)	Antagonism of dopamine	Antiparkinsonian agents helpful
Neuroleptic malignant syndrome	Catatonia, stupor, fever, unstable blood pressure, myoglobinemia; can be fatal	One or more weeks (can persist for days after stopping medication)	Antagonism of dopamine may contribute	Stop medication immediately; dantrolene (Dantrium) or bromocriptine (Parlodel)‡ may be helpful; antiparkinsonian agents not effective
Perioral tremor (i.e., rabbit syndrome)	Perioral tremor (may be a late variant of parkinsonism)	After months or years	Unknown	Antiparkinsonian agents often helpful
Tardive dyskinesia	Oral facial dyskinesia; widespread choreoathetosis or dystonia	After months or years (worse on withdrawal)	Excess function of dopamine hypothesized	Prevention crucial; treatment unsatisfactory