Pharmacology · Antipsychotic Drugs

Adverse Effects and Systematic Clinical Management

Extrapyramidal syndromes, tardive dyskinesia, neuroleptic malignant syndrome, metabolic effects, QTc risk, and hyperprolactinemia

This module gathers the adverse effect landscape across the entire antipsychotic class into structured reference panels. The organizing logic throughout is time: onset timing separates the extrapyramidal syndromes in the first table; the metabolic monitoring schedule is a timeline; NMS is distinguished from serotonin syndrome partly by its slower onset. Knowing when to expect something is how you catch it.
The extrapyramidal syndrome table is a consolidation of material from Module 2. It is reproduced here with two additions: a risk factor column that identifies which patients are most vulnerable, and a treatment column that highlights the two counter-intuitive rules — anticholinergics are not first-line for akathisia, and anticholinergics worsen cognition in elderly patients with drug-induced parkinsonism.
The NMS card leads with the tetrad because the tetrad is what the diagnosis requires, and the comparison to serotonin syndrome is there because the two are commonly confused. The distinguishing sign is the quality of the motor abnormality: lead-pipe rigidity with bradyreflexia in NMS versus hyperreflexia and clonus in serotonin syndrome.
The metabolic monitoring card converts the abstract risk into a concrete schedule. The timing of the follow-up measurements — weight at 4, 8, and 12 weeks; glucose and lipids at 12 weeks, then annually — reflects the evidence base for when metabolic changes become detectable. Metformin has the strongest evidence for pharmacological management of antipsychotic-induced weight gain.
The QTc table is a cross-class ranking built for rapid clinical use: when adding a QTc-active comedication, the table identifies which antipsychotics require caution and which are effectively neutral. The partial agonists at the bottom carry negligible QTc burden, which is one of their underappreciated advantages in medically complex patients.

Extrapyramidal Syndromes — Quick Reference

Syndrome	Onset	Key Features	Risk Factors	Treatment
Acute Dystonia	Hours to days	Oculogyric crisis, torticollis, opisthotonus; laryngeal dystonia = airway emergency	Young males; antipsychotic-naive; high-potency agents	Benztropine or diphenhydramine IM or IV — rapid
Akathisia	Days to weeks	Subjective restlessness, urge to move; danger: mistaken for worsening psychosis	All antipsychotics; partial agonists at higher doses	Propranolol first-line; dose reduction; benzodiazepines short-term. Anticholinergics NOT first-line
Drug-Induced Parkinsonism	Weeks	Bradykinesia, rigidity, tremor; identical to Parkinson disease at examination	Elderly; high-potency agents; dose-dependent	Dose reduction preferred; benztropine or amantadine if needed. Caution: anticholinergics worsen cognition
Tardive Dyskinesia	Months to years	Repetitive orofacial movements (lip smacking, tongue protrusion); may be irreversible	Older age; female; high cumulative dose; first-generation agents	Minimize dose or switch agent; valbenazine or deutetrabenazine (vesicular monoamine transporter 2 inhibitors) for established cases

Neuroleptic Malignant Syndrome and Metabolic Monitoring

Neuroleptic Malignant Syndrome

Tetrad: Hyperthermia + Lead-pipe rigidity + Autonomic instability + Altered consciousness
Lab: Markedly elevated creatine kinase (rhabdomyolysis)
Onset: 24–72 hours (slow vs. serotonin syndrome)
vs. Serotonin syndrome: Rigidity + bradyreflexia (not hyperreflexia/clonus)
Treatment: Stop antipsychotic immediately + dantrolene + bromocriptine + intensive care unit
Rechallenge: Wait minimum 2 weeks after full resolution; use lowest-potency agent

Metabolic Syndrome Monitoring

Baseline: Weight/body mass index, waist circumference, blood pressure, fasting glucose/hemoglobin A1c, lipid panel
Follow-up weight: At 4, 8, and 12 weeks
Fasting glucose and lipids: At 12 weeks, then annually
Highest risk agents: Clozapine > olanzapine > quetiapine
If >5% weight gain: Dietary counseling, exercise referral, consider switch or metformin
Best pharmacological adjunct: Metformin — strongest evidence base for antipsychotic-induced weight gain

QTc Prolongation Risk by Agent

Agent(s)	QTc Risk Level	Clinical Note
Thioridazine, pimozide	Highest — last resort	hERG channel blockade; risk of torsades de pointes; rarely used
Ziprasidone, haloperidol (intravenous), iloperidone	Moderate — monitor	Baseline electrocardiogram required; avoid in known QTc prolongation
Clozapine, olanzapine, quetiapine, risperidone	Low — nonzero	Assess when adding QTc-active comedications
Aripiprazole, brexpiprazole, cariprazine, lurasidone	Negligible	No meaningful QTc effect at therapeutic doses

Hyperprolactinemia: Highest with risperidone, paliperidone, and high-potency first-generation antipsychotics. Absent with clozapine, quetiapine, and partial agonists. Consequences: amenorrhea, galactorrhea, sexual dysfunction, gynecomastia, reduced bone density. Management: switch to prolactin-sparing agent, or add low-dose aripiprazole to existing regimen.

Tardive dyskinesia treatment: Valbenazine (once daily) and deutetrabenazine (twice daily) — vesicular monoamine transporter 2 inhibitors approved specifically for tardive dyskinesia. Treat without stopping the antipsychotic. Monitor for depression/suicidality — class adverse effect. Contraindicated in untreated depression or active suicidality.

Suggested References

Author / Organization	Title	Source
Katzung BG, ed.	Basic and Clinical Pharmacology. 15th ed.	McGraw-Hill; 2021
Brunton LL, Knollmann BC, eds.	Goodman & Gilman's The Pharmacological Basis of Therapeutics. 14th ed.	McGraw-Hill; 2023
Stahl SM	Stahl's Essential Psychopharmacology: Neuroscientific Basis and Practical Applications. 4th ed.	Cambridge University Press; 2013:129–237
Kane JM, Fleischhacker WW, Hansen L, Perlis R, Pikalov A, Assunção-Talbott S	Akathisia: an updated review focusing on second-generation antipsychotics	J Clin Psychiatry. 2009;70(5):627–643
Correll CU, Leucht S, Kane JM	Lower risk for tardive dyskinesia associated with second-generation antipsychotics: a systematic review of 1-year studies	Am J Psychiatry. 2004;161(3):414–425
Hauser RA, Factor SA, Marder SR, et al.	KINECT 3: a phase 3 randomized, double-blind, placebo-controlled trial of valbenazine for tardive dyskinesia	Am J Psychiatry. 2017;174(5):476–484
Anderson KE, Stamler D, Davis MD, et al.	Deutetrabenazine for treatment of involuntary movements in patients with tardive dyskinesia (AIM-TD): a double-blind, randomised, placebo-controlled, phase 3 trial	Lancet Psychiatry. 2017;4(8):595–604
Strawn JR, Keck PE Jr, Caroff SN	Neuroleptic malignant syndrome	Am J Psychiatry. 2007;164(6):870–876
De Hert M, Detraux J, van Winkel R, Yu W, Correll CU	Metabolic and cardiovascular adverse effects associated with antipsychotic drugs	Nat Rev Endocrinol. 2011;8(2):114–126
Fiedorowicz JG, Miller DD, Bishop JR, et al.	Systematic review and meta-analysis of pharmacological interventions for weight gain from antipsychotics and mood stabilizers	Curr Psychiatry Rev. 2012;8(1):25–36
Glassman AH, Bigger JT Jr	Antipsychotic drugs: prolonged QTc interval, torsade de pointes, and sudden death	Am J Psychiatry. 2001;158(11):1774–1782
Meltzer HY, Massey BW	The role of serotonin receptors in the action of atypical antipsychotic drugs	Curr Opin Pharmacol. 2011;11(1):59–67
Citrome L	Clozapine for schizophrenia: life-threatening or life-saving treatment?	Curr Psychiatry. 2009;8(12):56–63