Kventiax (Quetiapine)

• Quetiapine, an atypical antipsychotic, is employed across several psychiatric disorder categories to modulate neurotransmitter activity.
• Schizophrenia: alleviates positive symptoms such as delusions and hallucinations, and improves negative symptoms, supporting functional recovery in adult patients.
• Bipolar disorder (manic episodes): reduces mania severity, stabilizes mood swings, and helps prevent recurrence of elevated mood states when used as monotherapy or adjunct.
• Major depressive disorder (adjunct therapy): enhances antidepressant efficacy when added to standard treatments, improving mood, sleep, and overall depressive symptomatology.

• Quetiapine exerts its therapeutic effect primarily by antagonizing serotonin 5‑HT2A and dopamine D2 receptors, with additional activity at histamine H1, α1‑adrenergic and muscarinic receptors. This receptor profile modulates neurotransmission in cortical and limbic pathways, reducing psychotic and mood symptoms while producing sedative effects at higher doses. The combined blockade leads to a balanced reduction of dopaminergic overactivity in mesolimbic circuits while preserving dopaminergic transmission in the nigrostriatal pathway, which helps limit extrapyramidal side effects.

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

Common Side Effects

• Drowsiness: sedation or sleepiness, especially during dose titration.
• Dry mouth: reduced salivation causing oral discomfort.
• Constipation: slowed gastrointestinal motility leading to infrequent stools.
• Weight gain: increased appetite and gradual body weight increase.
• Orthostatic dizziness: light‑headedness upon standing due to blood pressure changes.

Serious or Rare Side Effects

• Neuroleptic malignant syndrome: rare, life‑threatening reaction with fever, muscle rigidity, autonomic instability.
• Agranulocytosis: severe reduction in white blood cells, increasing infection risk.
• Torsades de pointes: rare cardiac arrhythmia associated with QT prolongation.
• Severe hypotension: sudden drop in blood pressure causing fainting.
• Hepatic injury: rare liver enzyme elevations requiring monitoring.

• When prescribing quetiapine, clinicians should consider several safety measures.
• Monitor metabolic parameters: regularly assess weight, fasting glucose, and lipid profile.
• Assess for suicidal thoughts: especially in patients with depressive features.
• Evaluate cardiovascular status: caution in individuals with history of hypotension or arrhythmia.
• Review hepatic and renal function: dose adjustments may be required in impairment.
• Avoid abrupt discontinuation: taper under medical supervision to reduce withdrawal symptoms.
• Store at ambient temperature: keep below 25 °C in the original packaging, protect from moisture.

Quetiapine can interact with various medicines, influencing its efficacy or safety.

Major Interactions (Avoid)

• CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase quetiapine plasma levels.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce therapeutic effect.
• CNS depressants (alcohol, benzodiazepines): additive sedation and respiratory depression risk.
• Antihypertensives: may enhance orthostatic hypotension.

Moderate Interactions (Monitor Closely)

• Antidepressants (SSRIs, SNRIs): potential for serotonin syndrome.
• Anticholinergic drugs: increased anticholinergic burden.
• Digoxin: may raise serum digoxin concentrations.