Drug Guide
Quetiapine Fumarate
Classification
Therapeutic: Antipsychotic, ESD (Extended Second-Generation Antipsychotic)
Pharmacological: Atypical antipsychotic
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/ANursing Implications
Assessment: Monitor mental status, effectiveness of symptoms; observe for side effects such as weight gain, blood sugar, lipids.
Diagnoses:
- Risk for metabolic syndrome
- Risk for falls due to orthostatic hypotension
- Risk for sedation-related injury
Implementation: Administer with food to reduce orthostatic hypotension; monitor blood glucose, lipids; educate patients about adherence and side effects.
Evaluation: Assessment of symptom control, weight, metabolic parameters, and adverse effects.
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.