Ketrel (Quetiapine)

Quetiapine is an atypical antipsychotic that modulates dopamine and serotonin pathways, and is indicated for several psychiatric conditions.

• Schizophrenia: reduces psychotic symptoms and lowers risk of relapse.
• Bipolar I disorder (manic episodes): stabilises mood and controls manic symptoms.
• Bipolar I disorder (depressive episodes): alleviates depressive symptoms.
• Adjunctive treatment of major depressive disorder: enhances response to primary antidepressants.

• Quetiapine acts as an antagonist at dopamine D2 and serotonin 5‑HT2A receptors, while also modulating 5‑HT1A, histamine H1 and adrenergic α1 receptors. This receptor profile leads to balanced neurotransmission, decreasing dopaminergic overactivity linked to psychosis and normalising serotonergic pathways involved in mood regulation.

Quetiapine may cause a range of adverse reactions, from mild to serious. Awareness of common and rare events helps clinicians monitor patients effectively.

Common Side Effects

• Sedation or somnolence
• Dizziness or light‑headedness
• Dry mouth
• Constipation
• Weight gain
• Orthostatic hypotension

Serious or Rare Side Effects

• Neuroleptic malignant syndrome
• Agranulocytosis or severe leukopenia
• Tardive dyskinesia
• Significant QT‑interval prolongation
• Increased suicidal thoughts in young adults
• Severe hypotension or cardiovascular collapse

Quetiapine requires careful monitoring for metabolic, cardiovascular and psychiatric safety.

• Metabolic monitoring: regularly assess weight, glucose and lipid levels.
• Suicidality assessment: watch for emergence or worsening of suicidal thoughts, especially in younger patients.
• Elderly caution: avoid use in dementia‑related psychosis due to increased mortality risk.
• Discontinuation: taper gradually to reduce risk of rebound insomnia or agitation.
• Hepatic/renal function: adjust use in patients with significant impairment.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Quetiapine interacts with several drug classes; some combinations should be avoided while others need close monitoring.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine levels.
• Other antipsychotics: additive CNS effects and QT prolongation.
• CNS depressants (alcohol, benzodiazepines): heightened sedation and respiratory depression.
• Drugs that prolong QT interval (e.g., certain antiarrhythmics): risk of cardiac arrhythmias.
• Monoamine oxidase inhibitors: potential for hypertensive crisis.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce efficacy.
• Antihypertensive agents: additive hypotensive effect.
• Anticholinergic medications: may worsen dry mouth and constipation.
• Lithium: monitor lithium levels for possible toxicity.
• Smoking (induction of CYP1A2): may modestly affect plasma concentrations.