Generic Name

Quetiapine Fumarate

---

Classification

FDA Approved Indications

• Schizophrenia
• Bipolar disorder (mania and depression)
• Major depressive disorder (adjunct)

Mechanism of Action

Quetiapine acts as an antagonist at multiple neurotransmitter receptors in the brain, including dopamine D2 receptors and serotonin 5-HT2A receptors, which helps modulate neurotransmission involved in psychosis and mood regulation.

Dosage and Administration

Adult: Typically, starting dose is 25 mg twice daily, titrated up based on response and tolerability, with typical ranges of 150-800 mg/day depending on the indication.

Pediatric: Not generally recommended for children under 10 years old due to limited data.

Geriatric: Use with caution; initiate at lower doses due to increased sensitivity in older adults.

Renal Impairment: No specific dose adjustment needed but monitor closely.

Hepatic Impairment: Use with caution; start at lower doses, titrate carefully.

Pharmacokinetics

Absorption: Well absorbed after oral administration, with bioavailability approximately 9-17%.

Distribution: Highly protein-bound (~83%) and extensively distributed.

Metabolism: Primarily by hepatic CYP3A4 enzyme.

Excretion: Metabolites excreted in urine and feces.

Half Life: Approximately 6 hours for immediate-release form; XR has a longer half-life, around 7 hours.

Contraindications

• Hypersensitivity to quetiapine or any components.
• Use cautiously in patients with cardiovascular disease, cerebrovascular disease, seizures, or a history of diabetic ketoacidosis.

Precautions

• Monitor for metabolic syndrome, weight gain, and lipid abnormalities.
• Watch for signs of neuroleptic malignant syndrome.
• Use cautiously in elderly patients with dementia-related psychosis; risk of death.

Adverse Reactions - Common

• Drowsiness, dizziness, orthostatic hypotension (Common)
• Dry mouth, constipation, weight gain (Common)
• Fatigue, tremor (Common)

Adverse Reactions - Serious

• Extrapyramidal symptoms (Less common)
• Tardive dyskinesia (Uncommon)
• Neuroleptic malignant syndrome (Rare)
• QT prolongation, arrhythmias (Rare)
• Increased risk of mortality in elderly with dementia-related psychosis (Seen in some cases)

Drug-Drug Interactions

• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) increase levels; inducers (e.g., carbamazepine) decrease effectiveness.
• Other CNS depressants may enhance sedation.

Drug-Food Interactions

• Avoid alcohol and other CNS depressants.
• Grapefruit juice may increase plasma levels.

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication as prescribed, even if feeling well.
• Report signs of metabolic changes, severe dizziness, or unusual movements.
• Avoid alcohol and CNS depressants.
• Maintain regular follow-up appointments.

Special Considerations

Black Box Warnings:

• Increased risk of death in elderly patients with dementia-related psychosis.
• Suicidal thoughts and behaviors (for some indications)

Genetic Factors: Genetic variation in CYP3A4 may affect metabolism.

Lab Test Interference: None significant.

Overdose Management

Signs/Symptoms: Drowsiness, tachycardia, hypotension, EPS, coma, QT prolongation.

Treatment: Supportive care, activated charcoal if early, cardiac monitoring, manage hypotension, IV fluids.

Storage and Handling

Storage: Store at room temperature, 20-25°C (68-77°F).

Stability: Stable under recommended conditions.