Kventiax Sr (Quetiapine)

Quetiapine is used in several psychiatric conditions that involve dysregulation of dopamine and serotonin pathways.

• Schizophrenia: reduces psychotic symptoms such as hallucinations and delusions.
• Bipolar disorder (manic and depressive episodes): stabilises mood and prevents relapse of manic or depressive episodes.
• Major depressive disorder (adjunct therapy): enhances antidepressant response when added to standard treatment.

• Quetiapine acts as an antagonist at dopamine D2 receptors and serotonin 5‑HT2A/2C receptors, while also blocking histamine H1 and adrenergic α1 receptors. It exhibits partial agonist activity at 5‑HT1A receptors, resulting in modulation of dopaminergic and serotonergic neurotransmission that underlies its antipsychotic and mood‑stabilising effects.

Quetiapine may cause a range of adverse reactions that vary in frequency and severity.

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.
• Dizziness: sensation of light‑headedness.

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.
• Seizures: increased risk of convulsive episodes.
• Suicidal thoughts: emergence or worsening of suicidal ideation.

When prescribing quetiapine, clinicians should consider several safety aspects.

• Cardiovascular monitoring: assess for orthostatic hypotension and ECG changes.
• Metabolic assessment: monitor weight, glucose, and lipid levels regularly.
• CNS depression: caution when combined with other sedatives or alcohol.
• Pregnancy and lactation: evaluate risk‑benefit as safety data are limited.
• Elderly patients: start at low doses and watch for increased sensitivity to side effects.
• Store at ambient temperature: keep in original container, protect from moisture and direct sunlight.

Quetiapine interacts with several drug classes that may alter its efficacy or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine plasma levels.
• CNS depressants (e.g., benzodiazepines, opioids): can enhance sedation and respiratory depression.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., carbamazepine, rifampin): may reduce quetiapine concentrations.
• Antihypertensives: additive effect on blood pressure lowering.
• Anticholinergic agents: may worsen dry mouth and constipation.