Tizanidine

Oral
Spasticity
Adult: In patient with multiple sclerosis or spinal cord injury or disease: Initially, 2 mg as a single dose, increase according to patient's requirement and response in increments of 2-4 mg daily at 3-4 days interval. Dose should be taken in 3-4 divided doses. Usual dose: 24 mg daily. Max: 36 mg daily.
Renal impairment:

CrCl (ml/min)	Dosage Recommendation
<25	Initially, 2 mg once daily, increase in increments of no more than 2 mg, according to patient's tolerability and response.

Hepatic impairment: Contraindicated.

Concomitant use with potent CYP1A2 inhibitors (e.g. fluvoxamine, ciprofloxacin). Hepatic impairment.

Patient with psychiatric disorder, CV disorder, coronary artery disease. Renal impairment. Elderly. Pregnancy and lactation. Avoid abrupt dose reduction and withdrawal. Patient Counselling This drug may cause drowsiness, dizziness, and hypotension, if affected, do not drive or operate machinery. Monitoring Parameters Monitor LFT at baseline and monthly for the first 4 months of therapy. Monitor blood pressure, renal function, and ECG periodically.

Significant: Hepatotoxicity, hypersensitivity reactions, hypotension, sedation, hallucinations. Gastrointestinal disorders: Xerostomia. General disorders and administration site conditions: Weakness, fatigue, withdrawal hypertension. Infections and infestations: Infection. Investigations: Increased liver enzymes. Nervous system disorders: Dizziness, drowsiness. Cardiac disorders: Bradycardia, tachycardia.

Symptoms: Nausea, vomiting, hypotension, bradycardia, QT prolongation, dizziness, miosis, respiratory distress, coma, restlessness, somnolence. Management: Symptomatic and supportive treatment. Employ gastric lavage or administer high doses of activated charcoal. Maintain adequate hydration.

Enhanced CNS effects with sedatives and other CNS depressants (e.g. benzodiazepines, opioids, TCA). Increased hypotensive effects, rebound hypertension and tachycardia with β-adrenoceptor blockers, digoxin. Increased plasma concentration with oral contraceptives.
Potentially Fatal: Increased serum concentration with potent CYP1A2 inhibitors (e.g. fluvoxamine, ciprofloxacin).

Enhanced CNS effects with alcohol.

Tizanidine is an α₂-adrenergic agonist that acts on the spinal and supraspinal levels to block excitatory interneurons. It reduces spasticity by increasing presynaptic inhibition and has great effects in the polysynaptic pathways. It also possesses a moderate central analgesic effect.
Onset: 1-2 hours.
Duration: 3-6 hours.
Absorption: Well absorbed from the gastrointestinal tract. Food alters absorption and bioequivalence. Bioavailability: Approx 40% (oral). Time to peak plasma concentration: Approx 1 hour.
Distribution: Volume of distribution: 2.4 L/kg. Plasma protein binding: Approx 30%.
Metabolism: Undergoes extensive first-pass hepatic metabolism by CYP1A2 to inactive metabolites.
Excretion: Mainly via urine (60%); faeces (20%). Elimination half-life: Approx 2.5 hours.

Oral: Store at 25°C

Muscle Relaxants

M03BX02 - tizanidine ; Belongs to the class of other centrally-acting muscle relaxants.