Kventiax (Quetiapine)

Quetiapine is used in the treatment of several psychiatric disorders by modulating dopamine and serotonin pathways.

• Schizophrenia: reduces hallucinations, delusions and other psychotic symptoms.
• Bipolar disorder (manic episodes): stabilises mood and diminishes mania severity.
• Bipolar disorder (depressive episodes): alleviates depressive symptoms when used alone or with other agents.
• Major depressive disorder (adjunctive): enhances response to primary antidepressants in patients with insufficient improvement.

• Quetiapine acts primarily as an antagonist at dopamine D2 and serotonin 5‑HT2A receptors, while also modulating histamine H1, adrenergic α1 and serotonin 5‑HT1A receptors. This receptor profile reduces dopaminergic transmission in mesolimbic pathways and balances serotonergic activity, contributing to antipsychotic and mood‑stabilising effects.

Quetiapine may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Drowsiness: feeling of sleepiness or fatigue.
• Dry mouth: reduced salivation leading to discomfort.
• Constipation: infrequent bowel movements or hard stools.
• Weight gain: increase in body weight over time.

Serious or Rare Side Effects

• Neuroleptic malignant syndrome: rare but life‑threatening reaction with fever and muscle rigidity.
• Agranulocytosis: severe reduction in white blood cells, increasing infection risk.
• Orthostatic hypotension: sudden drop in blood pressure causing dizziness or fainting.

When prescribing quetiapine, clinicians should consider several safety and handling precautions.

• Cardiovascular monitoring: assess blood pressure and heart rate regularly.
• Metabolic screening: check glucose, lipid profile, and weight periodically.
• CNS depression: avoid operating machinery or driving if drowsiness occurs.
• Pregnancy and lactation: use only if benefits outweigh potential risks.
• Drug discontinuation: taper dose gradually to reduce withdrawal or relapse risk.
• Store at ambient temperature: keep below 25 °C in original packaging, protect from moisture.

Quetiapine can interact with other medicines, affecting its efficacy or safety.

Major Interactions (Avoid)

• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine plasma levels, raising toxicity risk.
• CNS depressants (e.g., benzodiazepines, opioids): additive sedation and respiratory depression.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may lower quetiapine concentrations, reducing effectiveness.
• Antihypertensives: enhanced orthostatic hypotension.
• Anticholinergic agents: may worsen dry mouth and constipation.