Quetiapine: clinical use

Prescribing considerations

• Confirm the indication and formulation because immediate-release, prolonged-release and liquid products differ in administration and licensing scope.
• Assess suicide and self-harm risk, sedation, falls, orthostatic hypotension, movement disorders, constipation, swallowing or aspiration risk, seizures and misuse history.
• Use particular caution with hepatic impairment, cardiovascular disease, QT prolongation, electrolyte disturbance, diabetes risk and concurrent anticholinergic or sedating medicines.
• Quetiapine is not approved for dementia-related psychosis; older adults with dementia have increased cerebrovascular and mortality concerns with antipsychotics.

Contraindications and cautions

• Hypersensitivity to quetiapine or a product excipient.
• Concurrent strong CYP3A4 inhibitors, including HIV protease inhibitors, azole antifungals, erythromycin, clarithromycin and nefazodone.

Monitoring

• Assess weight, glucose and lipids before treatment and periodically thereafter.
• Review blood pressure, sedation, falls risk and extrapyramidal symptoms according to clinical risk.
• Consider ECG and electrolyte assessment with cardiac disease, QT-prolonging medicines or other arrhythmia risks.
• Check a blood count promptly if fever, sore throat, infection or unexplained weakness develops.
• Monitor mental state and suicidality, especially after initiation, treatment changes or interruption.
• Monitor bowel function and investigate severe or persistent constipation urgently.

Clinical pharmacology

Quetiapine antagonises serotonin 5-HT2 and dopamine D1/D2 receptors. Norquetiapine also inhibits the noradrenaline transporter, partially agonises 5-HT1A receptors and has muscarinic activity. Metabolism is predominantly hepatic through CYP3A4.

Formulation and product differences

• Standard film-coated tablets are immediate-release and may be taken with or without food.
• Biquelle XL is prolonged-release, should be taken without food and swallowed whole; its selected licence also includes add-on treatment of major depressive disorder.
• Rosemont oral suspension must be shaken and measured with its supplied device. It contains sodium, propylene glycol, benzoic acid and parabens.
• Selected tablet products contain lactose; liquid excipients and storage requirements differ.

Modified-release tablet

Route: Oral

Strengths: 50 mg, 150 mg, 200 mg, 300 mg, 400 mg, 600 mg