Adverse Effects of Atypical Antipsychotics

Metabolic Adverse Effects

The American Academy of Child and Adolescent Psychiatry notes that atypical antipsychotics cause significant metabolic disturbances, including weight gain, which represents the most common significant problem associated with atypical antipsychotic use and may be extreme 1
Atypical antipsychotics can cause acute dystonia, laryngeal dystonia, akathisia, and drug-induced Parkinsonism, with risperidone carrying the highest risk among atypicals 2

Tardive dyskinesia occurs in 5% of young patients per year and is more common with typical antipsychotics, though it can occur with any atypical agent, characterized by rapid involuntary facial movements and extremity or truncal movements 3
Neuroleptic malignant syndrome is a potentially lethal syndrome consisting of mental status changes, fever, hypertonicity or rigidity, and autonomic dysfunction, with incidence ranging from 0.02% to 3% and mortality decreased to less than 10-15% 3
Antipsychotic medications lower the seizure threshold in a dose-dependent manner, though seizures are rare (usually <1%) at therapeutic doses, except for clozapine which has a 5% incidence at high dosages 3

Orthostatic hypotension is a common side effect requiring caution in patients with known cardiovascular or cerebrovascular disease 1
Minor electrocardiogram changes have been associated with atypical antipsychotics, raising concerns as youth may be more susceptible to cardiac effects 1

Agranulocytosis is a potential adverse effect primarily associated with clozapine, though it can occur with any antipsychotic agent 3
Weekly blood cell counts are required during first 6 months of clozapine treatment, then every 2 weeks thereafter, including 4 weeks after discontinuation 1

Atypical antipsychotics show consistent benefits in fine motor function, memory, and executive function compared to typical antipsychotics, causing fewer cognitive difficulties 1

Regular clinical monitoring is essential to identify potential changes early, including baseline and follow-up laboratory tests (renal and liver function, complete blood counts, electrocardiograms) as indicated for specific agents 4
Monitor for neurological side effects, especially extrapyramidal symptoms and tardive dyskinesia, particularly with long-term use 5

Atypical antipsychotics can cause bradykinesia as part of drug‑induced Parkinsonism syndrome, although the incidence is lower than with typical antipsychotics. The effect results from dopamine D₂ receptor blockade in the nigrostriatal pathways, producing the classic parkinsonian triad of bradykinesia, rigidity, and tremor. This drug‑induced Parkinsonism is one of three acute extrapyramidal syndromes (the others being acute dystonia and akathisia) associated with antipsychotic therapy. 6

Quetiapine and olanzapine are associated with an intermediate‑low risk of extrapyramidal symptoms (including bradykinesia) compared with other atypical agents. 7

Early recognition and rapid withdrawal or dose reduction of the offending antipsychotic markedly improves the likelihood of complete recovery from drug‑induced bradykinesia. 6
Clinical decision based on remission status
- If the patient is in full remission, maintain the current antipsychotic dose only when dose alteration would risk precipitating relapse. 8
- If the patient is not in full remission, proceed to medication adjustment. 8
Medication‑adjustment options (supported by the cited literature)
- Reduce the current antipsychotic dose. 6, 8
- Switch to an atypical antipsychotic with a lower EPS risk—preferably clozapine or quetiapine. 6, 7
- Add a short‑term anticholinergic agent (e.g., benztropine) during the acute phase, with plans for reassessment. 6
- Add amantadine, a dopaminergic agonist, as an adjunctive therapy. 6
Chronic anticholinergic therapy should be avoided, especially in elderly patients, and all patients should be re‑evaluated after the acute phase to determine ongoing need. 6, 7

Perform a baseline assessment of abnormal movements before initiating antipsychotic treatment, then repeat the evaluation every 3–6 months using standardized scales such as the Abnormal Involuntary Movement Scale (AIMS). 8
Tardive dyskinesia develops in approximately 5 % of young patients each year while on antipsychotic therapy, underscoring the importance of regular monitoring. 6