Kventiax Sr (Quetiapine)

Quetiapine is an atypical antipsychotic used across several psychiatric conditions.

• Schizophrenia: helps reduce psychotic symptoms such as hallucinations and delusions.
• Bipolar I disorder (manic and depressive episodes): stabilises mood and prevents relapse of manic or depressive swings.
• Adjunctive treatment of major depressive disorder: enhances antidepressant response when added to standard therapy.

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

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

Common Side Effects

• Drowsiness: feeling unusually sleepy or fatigued.
• Dry mouth: reduced salivation leading to discomfort.
• Constipation: infrequent or difficult bowel movements.
• Weight gain: increase in body weight over time.
• Orthostatic hypotension: drop in blood pressure upon standing.
• Elevated cholesterol or triglycerides: changes in lipid profile.

Serious or Rare Side Effects

• Neuroleptic malignant syndrome: rare but life‑threatening reaction with fever and muscle rigidity.
• Tardive dyskinesia: persistent involuntary movements, especially of the face.
• Agranulocytosis: severe reduction in white blood cells.
• Suicidal thoughts: emergence or worsening of suicidal ideation.
• Severe allergic reactions: rash, swelling, or breathing difficulty.

Before prescribing quetiapine, clinicians should consider several safety factors.

• Cardiovascular assessment: monitor blood pressure and heart rate, especially in patients with pre‑existing hypertension.
• Metabolic monitoring: check weight, glucose, and lipid levels regularly.
• CNS depression: advise caution when combined with other sedatives or alcohol.
• Elderly patients: start at low doses and watch for increased sensitivity to side effects.
• Pregnancy and lactation: use only if potential benefit justifies potential risk, as safety data are limited.
• Storage: Store below 25°C: keep in the original container, protect from moisture and direct sunlight.

Quetiapine can interact with several drug classes, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine plasma levels, raising toxicity risk.
• CNS depressants (e.g., benzodiazepines, opioids): can cause excessive sedation or respiratory depression.

Moderate Interactions (Monitor Closely):\n- CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce quetiapine concentrations, diminishing therapeutic effect.

• Antihypertensives: additive blood‑pressure‑lowering effect may lead to orthostatic hypotension.
• Anticholinergic agents: may exacerbate dry mouth and constipation.