Tizanide

# Tizanide ## Overview - **Classification**: Alpha-2 adrenergic agonist, centrally acting skeletal muscle relaxant. - **Mechanism**: Acts as an alpha-2 adrenergic agonist at presynaptic receptors in the spinal cord, inhibiting the release of excitatory amino acids and thereby reducing motor neuron activity and muscle tone. ## Primary Indications 1. **Spasticity Management** - Symptomatic treatment of increased muscle tone (spasticity) associated with multiple sclerosis, spinal cord injury, or other neurological conditions. ## Adult Dosing ### Standard Dosing **Spasticity** - **Dose**: Initial **2 mg** orally. - **Frequency**: Every 6-8 hours as needed. - **Route**: Oral. - **Titration**: May increase by **2-4 mg/day** at intervals of 1-4 days to achieve desired response. - **Maximum Dose**: **36 mg/day** (divided doses). ### Dose Adjustments - **Renal Impairment**: CrCl < 25 mL/min: Reduce initial dose to **2 mg once daily**, then titrate carefully and slowly. - **Hepatic Impairment**: Not recommended in severe hepatic impairment. Use with caution in mild-moderate; monitor LFTs closely. - **Elderly Patients**: Start with lower doses (e.g., **2 mg once daily**) and titrate slowly due to increased sensitivity and risk of adverse effects. ## Pediatric Dosing *(Tizanidine is not FDA-approved for pediatric use. Safety and efficacy have not been established in pediatric patients.)* ### Neonates (0-28 days) - **Dose**: Not recommended. - **Special Notes**: Safety and efficacy are not established. ### Infants (1-12 months) - **Dose**: Not recommended. - **Special Notes**: Safety and efficacy are not established. ### Children (1-12 years) - **Dose**: Not recommended. - **Special Notes**: Safety and efficacy are not established. Limited off-label use for severe spasticity may occur under specialist supervision, but generally avoided. ### Adolescents (13-18 years) - **Dose**: Not recommended for routine use. If considered (off-label) for severe spasticity, adult dosing principles may be applied cautiously, starting with the lowest dose. - **Maximum**: **36 mg/day**. - **Special Notes**: Closely monitor for adverse effects, especially hypotension and sedation. Consultation with a neurology specialist is advised. ## Safety Information ### Contraindications - **Absolute**: Concomitant use with strong CYP1A2 inhibitors (e.g., **fluvoxamine**, **ciprofloxacin**). - **Absolute**: Hypersensitivity to tizanidine or any component. - **Relative**: Severe hepatic impairment. ### Common Adverse Effects - **Very Common (>10%)**: Dry mouth, somnolence (drowsiness), asthenia (weakness), dizziness. - **Common (1-10%)**: Bradycardia, hypotension, nervousness, blurred vision, pharyngitis, rhinitis, constipation, liver enzyme elevation. - **Serious but Rare**: Hepatotoxicity, severe hypotension, QT prolongation, psychotic-like symptoms. ### Key Drug Interactions - **Strong CYP1A2 Inhibitors (fluvoxamine, ciprofloxacin)**: Contraindicated due to significant increase in tizanidine levels, leading to severe hypotension and excessive sedation. - **Other CYP1A2 Inhibitors (oral contraceptives, zileuton, acyclovir)**: Increased tizanidine levels; requires dose reduction and close monitoring for adverse effects. - **Antihypertensives**: Additive hypotensive effects; monitor blood pressure closely. - **CNS Depressants (alcohol, benzodiazepines, opioids)**: Additive CNS depression (sedation, dizziness); avoid or use with extreme caution. ## Monitoring & Follow-up - **Before Treatment**: Baseline liver function tests (LFTs) and blood pressure (BP). - **During Treatment**: LFTs (at 1, 3, 6 months, then periodically or if symptoms of hepatic injury arise). Monitor BP regularly, especially during dose titration. - **Clinical Signs**: Watch for signs of liver injury (e.g., nausea, fatigue, dark urine, jaundice), severe hypotension, excessive sedation, or dizziness. ## Clinical Pearls - 💡 **Titration is Key**: Start with **2 mg** and increase slowly to minimize side effects, particularly hypotension and sedation. - 💡 **Food Effect**: Tizanidine absorption is increased when taken with food; administer consistently with or without food for stable drug levels. - 💡 **Avoid Abrupt Discontinuation**: Gradually reduce dose over 1-2 weeks to avoid rebound spasticity, tachycardia, and hypertension. - 💡 **Patient Counseling**: Advise patients against activities requiring mental alertness (driving, operating machinery) until tolerance is established due to potential drowsiness and dizziness. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.