Ketilept (Quetiapine Fumarate)

• Quetiapine is used in psychiatric disorders that involve dopamine and serotonin dysregulation.
• Schizophrenia: reduces psychotic symptoms such as hallucinations and delusions.
• Bipolar disorder (manic and depressive episodes): stabilizes mood and prevents recurrence of manic or depressive swings.
• Adjunctive treatment of major depressive disorder: enhances antidepressant response when added to standard therapy.

• Quetiapine exerts its effect by antagonizing serotonin 5‑HT2A and dopamine D2 receptors, while also modulating activity at 5‑HT1A, histamine H1, and α1‑adrenergic receptors. This receptor profile decreases dopaminergic transmission in mesolimbic pathways, mitigating psychosis, and balances serotonergic signaling, contributing to mood stabilization. The combined antagonism leads to reduced excitatory neurotransmission and a calming effect on neuronal circuits implicated in schizophrenia and bipolar disorder.

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

Common Side Effects

• Drowsiness: persistent sleepiness or reduced alertness that may affect daily activities.
• Dry mouth: decreased salivation causing oral discomfort and difficulty swallowing.
• Constipation: slowed gastrointestinal transit leading to infrequent, hard stools.
• Weight gain: gradual increase in body weight and possible changes in appetite.
• Dizziness: light‑headed sensation, especially upon standing, that may cause imbalance.
• Increased appetite: heightened desire for food, potentially contributing to weight changes.

Serious or Rare Side Effects

• Neuroleptic malignant syndrome: rare, life‑threatening reaction with high fever, muscle rigidity, autonomic instability and altered mental status.
• Agranulocytosis: severe drop in white blood cell count, markedly increasing risk of infections.
• Torsades de pointes: uncommon cardiac arrhythmia linked to QT interval prolongation, which can cause fainting or sudden cardiac events.

When prescribing quetiapine, clinicians should consider several precautionary measures to ensure safe use.

• Dose titration: start low and adjust gradually based on therapeutic response and tolerability.
• Cardiovascular monitoring: assess baseline ECG and monitor for QT prolongation, especially in patients with cardiac risk factors.
• Metabolic screening: regularly evaluate weight, glucose and lipid levels due to risk of metabolic changes.
• Elderly patients: use caution as increased sensitivity to sedation and orthostatic hypotension may occur.
• Pregnancy and lactation: avoid unless benefits outweigh potential risks, as safety data are limited.
• Store at ambient temperature: keep tablets below 25 °C in the original container, protected from moisture and light.

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

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase quetiapine plasma levels, raising risk of toxicity.
• CYP3A4 inducers (e.g., rifampicin, carbamazepine): can reduce quetiapine concentrations, potentially diminishing therapeutic effect.
• CNS depressants (e.g., alcohol, benzodiazepines, opioids): additive sedation and respiratory depression risk.

Moderate Interactions (Monitor Closely)

• Antihypertensives: quetiapine may enhance orthostatic hypotension, requiring blood pressure monitoring.
• Anticholinergic agents: combined use can exacerbate dry mouth, constipation, and cognitive effects.
• Lithium: concurrent therapy may increase risk of neurotoxicity; monitor lithium levels.