1. Dystonias: prolonged contraction of muscles during initiation, including painful muscle spasms; life-threatening if airway is compromised. Higher risk with younger males.
Centrally-acting anticholinergics (diphenhydramine, benztropine) can be used for prophylaxis or treatment. - may occur within a few hours to days of treatment
2. It also causes oculogyric crisis, which is a spasm of the extraocular muscles, causing an upward and outward position of the eyes.
3. After a few days to a month, there could be Akathisia or pseudo-parkinsonism.
Akathisia: restlessness with anxiety and an inability to remain still; treated with anticholinergics (diphenhydramine, benztropine), benzodiazepines or propranolol.
Pseudo-parkinsonism is characterized by muscle rigidity, usually in the facial muscles, giving the face a wooden, mask-like appearance.
Other symptoms include bradykinesia, (or slow movements), and tremors.
Treat with anticholinergics, or propranolol if tremor is the main symptom.
It's important to note that typical antipsychotics are more likely to cause these side effects compared to the atypical antipsychotics.
However, extrapyramidal symptoms usually disappear once the medication is stopped.
4. Tardive dyskinesia, which can present after several months or even years; is characterized by constant involuntary, rhythmic movements.
This typically happen with the perioral muscles causing the person to repeatedly smack, or purse their lips.
Unlike acute extrapyramidal symptoms, tardive dyskinesia can be irreversible, so the medication should be discontinued at the first sign of tardive dyskinesia.
Neuroleptic Malignant Syndrome or NMS, which typically starts days to weeks after starting the medications.
It's characterized by confusion, coma, agitation, muscle rigidity, seizures, and hyperthermia.
These symptoms are almost identical to serotonin syndrome, caused by antidepressants like selective serotonin reuptake inhibitors.
However, serotonin syndrome causes hyperreflexia and dilated pupils, while in neuroleptic malignant syndrome there's hyporeflexia and normal pupils.
If this condition progresses, it will cause rhabdomyolysis, where the muscles break down.
Treatment of neuroleptic malignant syndrome consists of administration of dantrolene, which is a muscle relaxant.
Typical antipsychotics also cause side effects by blocking other receptors: Alpha-1 receptor inhibition causes orthostatic hypotension;
- muscarinic receptor inhibition causes anticholinergic, or atropine-like side effects such as dry mouth, blurred vision, urinary retention, and constipation; and
- histamine H1 receptor inhibition causes sedation.
The low potency antipsychotics have a stronger sedating effect, but a low incidence of extrapyramidal symptoms.
Other side effects include prolongation of the QT interval, and metabolic side effects, such as weight gain, dyslipidemia, and hyperglycemia.
For medicine-specific side effects, chlorpromazine causes corneal deposits, while thioridazine causes retinal deposits within the eye.