💊 Atypical Antipsychotics

Atypical antipsychotics, or second-generation antipsychotics, are a class of medications used to treat psychotic disorders. They differ from typical antipsychotics in their receptor binding profile and generally have a lower propensity for extrapyramidal side effects.

These drugs primarily block dopamine D2 receptors, but also have significant serotonin 5-HT2A receptor antagonism. This serotonin-dopamine antagonism is thought to contribute to their reduced extrapyramidal side effect profile and potential efficacy for negative symptoms. They also interact with other receptors, including histamine and alpha-adrenergic.

Atypical antipsychotics are first-line treatment for schizophrenia and other psychotic disorders, including acute psychotic episodes. They are also indicated for bipolar disorder (manic, depressive, and maintenance phases) and treatment-resistant depression as an augmentation strategy. Some are used for irritability associated with autistic disorder.

Contraindications include known hypersensitivity to the drug. Caution is advised in patients with severe cardiovascular disease, history of seizures, and diabetes due to metabolic side effects. Specific contraindications vary by drug, e.g., clozapine has unique haematological contraindications.

Common adverse effects include metabolic syndrome (weight gain, dyslipidaemia, hyperglycaemia, increased risk of type 2 diabetes), sedation, and orthostatic hypotension. While generally lower than typical antipsychotics, EPS can still occur. QT prolongation is a risk, and some can cause hyperprolactinaemia.

Metabolic monitoring is crucial, including regular weight checks, fasting glucose, and lipid profiles. ECG monitoring is recommended before and during treatment to assess for QT prolongation. Blood pressure should be monitored, especially for orthostatic changes. Prolactin levels may be checked if symptoms of hyperprolactinaemia arise.

When prescribing, verify allergies and carefully review the patient's medical history for metabolic risk factors. Be vigilant for drug interactions, especially with other CNS depressants or QT-prolonging agents. Patient counselling should emphasise the importance of adherence, potential metabolic side effects, and the need for regular monitoring.

Key learning points include the concept of metabolic syndrome and its management in patients on atypical antipsychotics. The reduced risk of EPS compared to typical antipsychotics is a high-yield distinction. Understanding their broader range of indications beyond just psychosis, such as bipolar disorder, is important.

SBAs frequently test knowledge of the metabolic side effects of atypical antipsychotics and the necessary monitoring. Questions may compare the side effect profiles of typical vs. atypical antipsychotics, particularly regarding EPS. Understanding their role in bipolar disorder and treatment-resistant depression is also common.