Granisetron

# granisetron ## Overview - **Classification**: 5-HT3 Receptor Antagonist, Antiemetic - **Mechanism**: Selectively blocks serotonin 5-HT3 receptors on vagal nerve terminals and in the chemoreceptor trigger zone, preventing nausea and vomiting. ## Primary Indications 1. **Chemotherapy-Induced Nausea & Vomiting (CINV)** - Prevention and treatment 2. **Radiation-Induced Nausea & Vomiting (RINV)** - Prevention 3. **Postoperative Nausea & Vomiting (PONV)** - Prevention and treatment ## Adult Dosing ### Standard Dosing **Prevention of CINV (IV)** - **Dose**: **1 mg** - **Frequency**: Single dose - **Route**: IV, infused over 30 seconds or 5 minutes - **Timing**: Administer up to 30 minutes before chemotherapy **Prevention of CINV (Oral)** - **Dose**: **1 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Timing**: First dose 1 hour before chemotherapy, continue for up to 7 days after **Prevention of CINV (Transdermal Patch)** - **Dose**: **3.1 mg/24 hours** (continuous delivery) - **Frequency**: Apply once - **Route**: Transdermal - **Timing**: Apply 24-48 hours before chemotherapy, remove after 7 days **Prevention & Treatment of PONV (IV)** - **Dose**: **1 mg** - **Frequency**: Single dose - **Route**: IV, infused over 5 minutes - **Timing**: Before anesthesia induction or soon after surgery **Prevention of RINV (Oral)** - **Dose**: **2 mg** - **Frequency**: Once daily (QD) - **Route**: Oral - **Timing**: Start 1 day before radiation, continue during and for 1 day after ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment recommended. - **Hepatic Impairment**: No specific dose adjustment recommended; caution with severe impairment due to reduced clearance. - **Elderly Patients**: No specific dose adjustment necessary. ## Pediatric Dosing ### Neonates (0-28 days) - Safety and efficacy not established. Not recommended. ### Infants (1-12 months) - Safety and efficacy not established. Not recommended. ### Children (2-16 years) **Prevention of CINV (IV)** - **Dose**: **10 mcg/kg** (0.01 mg/kg) - **Frequency**: Single dose - **Route**: IV, infused over 5 minutes - **Maximum**: **1 mg/dose** - **Special Notes**: Administer 30 minutes prior to chemotherapy. **Prevention & Treatment of PONV (IV)** - **Dose**: **20 mcg/kg** (0.02 mg/kg) - **Frequency**: Single dose - **Route**: IV, infused over 5 minutes - **Maximum**: **1 mg/dose** - **Special Notes**: Administer before induction of anesthesia or post-surgery. ### Adolescents (13-18 years) - **Dose**: Adult dosing regimens apply. - **Maximum**: **1 mg/dose** IV or **2 mg/day** oral. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to granisetron or other 5-HT3 receptor antagonists. ### Common Adverse Effects - **Very Common (>10%)**: Headache, Constipation - **Common (1-10%)**: Diarrhea, Asthenia, Abdominal pain, Dyspepsia - **Serious but Rare**: Serotonin Syndrome, QTc prolongation, Hypersensitivity reactions (anaphylaxis, angioedema) ### Key Drug Interactions - **Serotonergic Drugs** (e.g., SSRIs, SNRIs, MAOIs, TCAs, tramadol, fentanyl): Increased risk of serotonin syndrome. Monitor for mental status changes, autonomic instability, neuromuscular abnormalities. - **Drugs that Prolong QTc** (e.g., antiarrhythmics, antipsychotics, macrolides, fluoroquinolones): Additive risk of QTc prolongation. Use with caution, especially in patients with pre-existing cardiac conditions. ## Monitoring & Follow-up - **Before Treatment**: Assess history of hypersensitivity to 5-HT3 antagonists. Assess cardiac history for QTc prolongation risk factors. - **During Treatment**: Monitor for signs/symptoms of serotonin syndrome if co-administered with serotonergic agents. ECG monitoring considered for patients with QTc risk factors. - **Clinical Signs**: Watch for headache, constipation, abdominal discomfort, or signs of allergic reaction. ## Clinical Pearls - 💡 **Prophylactic Use**: Best administered *before* chemotherapy, radiation, or surgery for optimal antiemetic effect. - 💡 **Transdermal Option**: The patch offers convenient, continuous 7-day antiemetic coverage for CINV. - 💡 **Bowel Obstruction**: Use with caution in patients with complete bowel obstruction due to potential reduction in gut motility. - 💡 **Patient Education**: Counsel patients on common side effects like headache and constipation and when to seek medical attention. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.