Kventiax Sr (Quetiapine)

Quetiapine is an atypical antipsychotic that modulates neurotransmission in psychotic and mood disorders.

• Schizophrenia: reduces hallucinations, delusions and other psychotic symptoms, improving functional outcomes.
• Bipolar disorder: stabilizes mood during manic and depressive phases, decreasing episode frequency.
• Major depressive disorder (adjunct therapy): enhances response to standard antidepressants when added to the regimen.
• Psychotic depression: alleviates psychotic features accompanying depressive episodes.

• Quetiapine acts as an antagonist at serotonin 5‑HT₂A, dopamine D₂, histamine H₁, and adrenergic α₁ receptors, with additional activity at other neurotransmitter sites. By blocking 5‑HT₂A and D₂ receptors, it reduces dopaminergic and serotonergic over‑activity implicated in psychosis and mood instability, while its antihistaminic and anti‑adrenergic effects contribute to its sedative and anxiolytic properties.

Quetiapine may cause a range of adverse reactions, varying in frequency and severity.

Common Side Effects

• Drowsiness: feeling of sleepiness or reduced alertness.
• Dry mouth: decreased salivation leading to oral 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.
• Tardive dyskinesia: persistent involuntary movements, especially of the face.
• Agranulocytosis: severe reduction in white blood cells, increasing infection risk.

When prescribing quetiapine, clinicians should consider several safety precautions to minimize risks.

• Assess cardiovascular status: monitor blood pressure and heart rate, especially in patients prone to orthostatic hypotension.
• Evaluate metabolic risk: screen for diabetes, lipid abnormalities, and weight changes before and during therapy.
• Review psychiatric history: monitor for emergence of suicidal thoughts or worsening depression.
• Consider hepatic and renal function: adjust use in patients with significant liver or kidney impairment.
• Avoid abrupt discontinuation: taper dose gradually to reduce risk of withdrawal symptoms.
• Store at ambient temperature: keep tablets in original container, protect from moisture and direct sunlight.

Quetiapine can interact with other medicines, altering its effectiveness or safety profile.

Major Interactions (Avoid)

• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine plasma levels, risking toxicity.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce quetiapine concentrations, diminishing efficacy.
• CNS depressants (e.g., benzodiazepines, opioids): additive sedation and respiratory depression.

Moderate Interactions (Monitor Closely)

• Antihypertensives: enhanced hypotensive effect when combined with quetiapine.
• Anticholinergic agents: may exacerbate dry mouth and constipation.
• Antidepressants (e.g., SSRIs, SNRIs): potential for increased serotonergic activity and QT prolongation.