What are the common adverse effects of second‑generation antipsychotics in adults and what baseline and follow‑up monitoring should be performed?

Common Adverse Effects of Second-Generation Antipsychotics

Second-generation antipsychotics (SGAs) cause significant metabolic side effects—particularly weight gain, hyperglycemia, and dyslipidemia—with clozapine and olanzapine carrying the highest risk, while aripiprazole and ziprasidone have the most favorable metabolic profiles. 1, 2, 3

Metabolic Adverse Effects

Weight Gain and Obesity

• Clozapine and olanzapine produce the greatest weight gain, with olanzapine causing mean increases of approximately 4 kg in short-term trials in youth and clozapine causing approximately 2.4 kg 4
• Risperidone and quetiapine cause moderate weight gain, with risperidone producing mean increases of 2 kg and quetiapine 1.7 kg in pediatric populations 4
• Aripiprazole causes minimal weight gain (approximately 0.9 kg), while ziprasidone is generally weight-neutral 3, 4
• Weight gain occurs early in treatment and is a major cause of medication discontinuation 1, 3

Hyperglycemia and Diabetes Mellitus

• Clozapine and olanzapine are strongly associated with increased risk of type 2 diabetes mellitus, with consistent evidence from multiple population-based studies 1, 2, 3
• Risperidone and quetiapine show mixed results, with some studies suggesting modest increased risk while others show no association 1, 2, 3
• Aripiprazole and ziprasidone do not appear to increase diabetes risk based on available clinical trial data 3
• Olanzapine increases glucose levels by approximately 2 mg/dL and risperidone by 3.7 mg/dL in youth 4
• Up to one-quarter of new-onset diabetes cases may occur without substantial weight gain, suggesting direct effects on glucose regulation independent of adiposity 3

Dyslipidemia

• Olanzapine and quetiapine cause the most significant lipid abnormalities, with olanzapine increasing triglycerides by approximately 20 mg/dL and cholesterol by 4.5 mg/dL, while quetiapine increases triglycerides by 19.5 mg/dL and cholesterol by 10.8 mg/dL in pediatric trials 4
• Clozapine is associated with increased likelihood of developing dyslipidemia in population-based studies 1
• Aripiprazole does not appear to increase dyslipidemia risk, while results for risperidone and ziprasidone are mixed 1, 3

Extrapyramidal Side Effects (EPS)

Acute EPS

• All SGAs produce fewer EPS than high-potency first-generation antipsychotics (particularly haloperidol), even at low doses 5
• Among SGAs, ziprasidone, olanzapine, aripiprazole, and risperidone carry the highest EPS risk in youth, with odds ratios of 20.6.4,3.8, and 3.7 respectively compared to placebo 4
• Clozapine, quetiapine, and low-dose olanzapine have the lowest EPS risk among SGAs 6
• Children and adolescents have higher EPS risk than adults, particularly young males for acute dystonia 6
• Acute dystonic reactions involve sudden spastic muscle contractions in the neck, eyes, or torso and require immediate treatment with benztropine 1-2 mg IM/IV or diphenhydramine 6

Tardive Dyskinesia

• Risk of tardive dyskinesia is lower with SGAs than typical antipsychotics but still occurs 7, 5
• Typical antipsychotics carry approximately 50% risk of tardive dyskinesia after 2 years of continuous use in young patients 6
• Requires assessment at least every 3-6 months using standardized measures 6

Akathisia

• Akathisia presents as subjective restlessness and physical agitation, often misinterpreted as anxiety or psychotic agitation 6
• It is a major cause of medication non-compliance 6
• First-line management is dose reduction, followed by switching to quetiapine or olanzapine, or adding propranolol 6

Cardiovascular Effects

QT Prolongation

• QT prolongation can occur with therapeutic dosing of any antipsychotic, with the most feared complication being torsades de pointes 8
• Quetiapine has been reported to cause QT prolongation 7
• Paliperidone carries warnings about QT prolongation and should be avoided in patients with risk factors for prolonged QT interval 9
• ECG monitoring is recommended in patients with cardiovascular risk factors or when using high doses 7

Orthostatic Hypotension

• Quetiapine causes orthostatic hypotension in 4-7% of patients 7
• Elderly patients have greater susceptibility to orthostatic hypotension 7
• Use caution in patients with known cardiovascular or cerebrovascular disease and those predisposed to hypotension 9
• Blood pressure monitoring is recommended, particularly when initiating therapy or increasing doses 7

Tachycardia

• Sinus tachycardia and other dysrhythmias are attributable to antipsychotics 8
• Tachycardia is a commonly observed adverse reaction in adults and adolescents with schizophrenia 9

Endocrine Effects

Hyperprolactinemia

• Risperidone causes the most significant prolactin elevation (OR 38.6 compared to placebo), followed by olanzapine (OR 15.6) and ziprasidone (OR 9.4) in youth 4
• Prolactin elevations occur and persist during chronic administration 9
• Symptomatic hyperprolactinemia requires switching to a prolactin-sparing agent like aripiprazole or quetiapine 6

Hematologic Effects

Leukopenia and Neutropenia

• Leukopenia, neutropenia, and agranulocytosis have been reported with antipsychotics, including paliperidone 9
• Patients with a history of clinically significant low white blood cell count or drug-induced leukopenia/neutropenia should have frequent CBC monitoring during the first few months of therapy 9
• Neutropenia risk may be higher in youth taking quetiapine, with five of 21 patients developing significant neutropenia in one study 7
• Quetiapine carries rare risk of leukopenia 7

Neurological Effects

Sedation and Somnolence

• All SGAs increase the risk of somnolence/sedation 4
• Quetiapine causes significant sedation, particularly in elderly patients who are at higher risk of cognitive impairment 7
• Somnolence is a commonly observed adverse reaction in adolescents with schizophrenia 9
• Potential for cognitive and motor impairment requires caution when operating machinery 9

Seizures

• Seizure risk appears elevated in youth taking quetiapine, with two of 21 youth experiencing seizures in clozapine comparison studies 7
• Use cautiously in patients with a history of seizures or conditions that lower the seizure threshold 9
• Quetiapine requires monitoring for seizures, particularly at higher doses 7

Neuroleptic Malignant Syndrome

• Neuroleptic malignant syndrome is a potential risk with all antipsychotics 7, 9
• Requires immediate discontinuation of drug and close monitoring 9

Gastrointestinal Effects

• Nausea and vomiting are the most common reasons for discontinuation of quetiapine, with overall discontinuation due to adverse effects ranging from 4-12.3% depending on indication 7
• Obstructive symptoms may result in patients with gastrointestinal narrowing disease due to the non-deformable tablet formulation of extended-release paliperidone 9

Hepatic Effects

• Elevations in hepatic transaminase levels may occur with quetiapine 7
• Baseline and periodic liver function tests are advised 7

Ophthalmologic Effects

• Quetiapine was associated with cataract development in animal studies, though this has not been confirmed in humans 7
• The FDA recommends baseline and 6-month follow-up eye examinations when prescribing quetiapine 7

Anticholinergic Effects

• Quetiapine has high central anticholinergic activity, which may worsen cognitive symptoms 7
• Antipsychotics may worsen the condition of patients who present with intoxication from drugs with anticholinergic properties 8

Special Population Considerations

Elderly Patients

• Elderly patients with dementia-related psychoses treated with atypical antipsychotics have increased incidence of cerebrovascular adverse reactions (e.g., stroke, transient ischemic attack, including fatalities) 9
• Dose reduction is recommended in older patients due to higher risk of sedation, cognitive impairment, and orthostatic hypotension 7

Children and Adolescents

• Children and adolescents may have significant unrecognized side effects and greater difficulty communicating concerns due to developmental issues 6
• Short-term metabolic effects and EPS are frequent in children treated with SGAs 4
• SGAs have distinct profiles of secondary effects in youth that differ from adults 4

Pregnancy

• May cause extrapyramidal and/or withdrawal symptoms in neonates with third trimester exposure 9

Baseline and Follow-Up Monitoring Requirements

Before Initiating Treatment

• Comprehensive metabolic baseline: BMI, waist circumference, blood pressure, HbA1c, fasting glucose, and fasting lipid panel 6, 7
• Hematologic evaluation: complete blood count and prolactin level 7
• Liver function tests (particularly for quetiapine and valproate combinations) 7
• Renal function tests: BUN, creatinine, urinalysis 6
• Thyroid function tests (if using lithium concurrently) 6
• Electrocardiogram in patients with cardiovascular risk factors 7
• Pregnancy test in females of childbearing potential 6
• Document any preexisting abnormal movements before initiating treatment 7

Intensive Monitoring (First 3 Months)

• BMI and waist circumference monthly for the first three months 6, 7
• Blood pressure at each clinical visit 6, 7
• Fasting glucose at 4 weeks 6, 7
• Repeat fasting glucose and lipid panel at 3 months 6, 7

Ongoing Monitoring (Every 3-6 Months)

• BMI quarterly after the initial intensive phase 6
• Blood pressure, fasting glucose, and fasting lipid panel annually after the 3-month assessment 6, 7
• HbA1c, renal function, and liver function annually 7
• Tardive dyskinesia assessment at least every 3-6 months using standardized measures 6

Common Pitfalls to Avoid

• Inadequate frequency of metabolic monitoring during the first three months can miss rapid weight gain and metabolic changes 6
• Failure to obtain baseline measurements prevents comparison and early detection of adverse effects 6
• Overlooking comorbid conditions (e.g., ADHD, anxiety, substance use) can complicate treatment response 6
• Underdosing or premature discontinuation when side effects occur instead of implementing appropriate management strategies 6
• Combining high-dose olanzapine with benzodiazepines, as fatalities have been reported 6
• Using prophylactic anticholinergics routinely rather than reserving them for treating symptoms when they occur 6