Fentanyl

# Fentanyl ## Overview - **Classification**: Opioid analgesic - **Mechanism**: Potent, synthetic phenylpiperidine opioid that acts primarily as a μ-opioid receptor agonist in the CNS. It alters the perception and emotional response to pain. ## Primary Indications 1. **Analgesia**: Management of chronic severe pain requiring continuous, around-the-clock opioid analgesia (transdermal). 2. **Acute Pain Management**: For severe acute pain (e.g., post-operative, breakthrough cancer pain) (IV, oral transmucosal). 3. **Anesthesia Adjunct**: As an opioid analgesic component of general and regional anesthesia. ## Adult Dosing ### Standard Dosing **Chronic Severe Pain (Transdermal Patch)** - **Dose**: Initial **12-25 mcg/hr** - **Frequency**: Apply new patch every **72 hours** - **Route**: Transdermal - **Special Considerations**: Not for acute pain. Titrate slowly by **12 or 25 mcg/hr** increments every 3 days. **Acute Severe Pain (IV)** - **Dose**: **25-100 mcg** - **Frequency**: Every **1-2 hours** as needed - **Route**: IV push over 1-2 minutes - **Maximum Dose**: Titrate to effect, typically **up to 200 mcg/dose** in acute settings. - **Special Considerations**: Rapid onset, short duration. Monitor closely for respiratory depression. **Anesthesia Adjunct (IV)** - **Dose**: **0.5-20 mcg/kg** depending on procedure and desired effect. - **Frequency**: Single dose or continuous infusion - **Route**: IV - **Special Considerations**: Administer slowly, monitor vital signs closely. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment guidelines. Use with caution. Monitor closely for prolonged effects. - **Hepatic Impairment**: Use with caution. Consider lower starting doses and slower titration. Monitor for increased adverse effects. - **Elderly Patients**: Start with lower doses (e.g., **half the usual starting dose**). Increased sensitivity to respiratory and CNS depressant effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Analgesia/Sedation - **Dose**: IV **0.5-2 mcg/kg/dose** - **Frequency**: Every **2-4 hours** as needed, or continuous infusion **0.5-5 mcg/kg/hr**. - **Maximum**: Max bolus **2 mcg/kg**. Max infusion **5 mcg/kg/hr**. - **Special Notes**: Longer half-life and increased sensitivity due to immature liver/renal function. Closely monitor for respiratory depression. ### Infants (1-12 months) - **Indication**: Analgesia/Sedation - **Dose**: IV **1-2 mcg/kg/dose** - **Frequency**: Every **2-4 hours** as needed, or continuous infusion **0.5-5 mcg/kg/hr**. - **Maximum**: Max bolus **2 mcg/kg**. Max infusion **5 mcg/kg/hr**. - **Special Notes**: Transdermal patches generally not recommended due to variable absorption and high risk of overdose. ### Children (1-12 years) - **Indication**: Analgesia/Sedation (IV), breakthrough cancer pain (oral transmucosal in opioid-tolerant). - **IV Dose**: **1-2 mcg/kg/dose** - **IV Frequency**: Every **2-4 hours** as needed, or continuous infusion **0.05-5 mcg/kg/hr**. - **Maximum**: Max bolus **2 mcg/kg**. Max infusion **5 mcg/kg/hr**. - **Transdermal**: Only for opioid-tolerant children **>2 years** and **>30 kg** already on opioid therapy. Initial dose **12 mcg/hr**. ### Adolescents (13-18 years) - **Indication**: Analgesia/Sedation - **Dose**: Generally follow **adult dosing guidelines** for IV and transdermal forms. - **Maximum**: Max IV bolus **100 mcg**. Max transdermal **100 mcg/hr**. - **Special Notes**: Careful titration is essential. Ensure opioid tolerance before transdermal use. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to fentanyl. - **Absolute**: Acute or severe bronchial asthma in an unmonitored setting. - **Absolute**: Significant respiratory depression. - **Absolute**: GI obstruction, paralytic ileus. - **Absolute**: Opioid non-tolerant patients (for transdermal/oral transmucosal). - **Absolute**: Management of acute or post-operative pain (transdermal). ### Common Adverse Effects - **Very Common (>10%)**: Nausea, vomiting, constipation, dizziness, somnolence, headache. - **Common (1-10%)**: Pruritus, dry mouth, sweating, confusion, respiratory depression. - **Serious but Rare**: Severe respiratory depression, apnea, bradycardia, seizures, serotonin syndrome (with serotonergic drugs), adrenal insufficiency, opioid-induced androgen deficiency, severe hypotension. ### Key Drug Interactions - **CYP3A4 Inhibitors (e.g., ketoconazole, ritonavir, erythromycin)**: Increase fentanyl plasma concentrations, prolonging opioid effects. **Avoid concomitant use** or use with extreme caution and reduce fentanyl dose. - **CNS Depressants (e.g., benzodiazepines, other opioids, alcohol)**: Increased risk of profound sedation, respiratory depression, coma, and death. **Avoid concomitant use**. If necessary, use lowest doses for shortest duration and monitor closely. - **Serotonergic Drugs (e.g., SSRIs, SNRIs, TCAs)**: Increased risk of serotonin syndrome. **Monitor for symptoms** like mental status changes, autonomic instability, neuromuscular abnormalities. - **MAOIs**: Potentiates opioid effects. **Contraindicated within 14 days** of MAOI use. ## Monitoring & Follow-up - **Before Treatment**: Assess pain level, respiratory status, history of substance abuse. For transdermal, confirm opioid tolerance. - **During Treatment**: - **Respiratory rate and depth**: Frequently, especially after initiation or dose titration. - **Sedation level**: Using a validated sedation scale. - **Blood pressure, heart rate**: Regularly. - **Pain score**: Regularly to assess efficacy. - **Bowel function**: Monitor for and manage constipation. - **Signs of opioid withdrawal**: If rapidly discontinued. - **Clinical Signs**: Watch for excessive sedation, pinpoint pupils, shallow breathing, confusion, dizziness, cool/clammy skin. ## Clinical Pearls - 💡 **Rapid Onset (IV)**: IV fentanyl has a very rapid onset (1-2 min) but short duration (30-60 min). Ideal for acute, severe pain needing quick relief. - 💡 **Transdermal Specifics**: ONLY for chronic, opioid-tolerant patients. Never use for acute pain or opioid-naive individuals due to delayed onset and prolonged effect (up to 24 hrs after patch removal). - 💡 **Patch Application**: Apply to a non-hairy skin site. Rotate sites to prevent irritation. Do not cut or damage patches. Fold used patches in half with adhesive sides together before disposal. - 💡 **Respiratory Depression**: The most significant and potentially fatal adverse effect. Always have naloxone readily available. - 💡 **Tolerance/Dependence**: Long-term use can lead to physical dependence and tolerance. Taper slowly to avoid withdrawal symptoms. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.