Tizanidine is a centrally acting alpha-2 adrenergic receptor agonist used primarily as a short-acting muscle relaxant. It reduces spasticity by increasing presynaptic inhibition of motor neurons, effectively decreasing the release of excitatory amino acids in the spinal cord interneurons. In the Indian context, it is a widely prescribed, cost-effective alternative to baclofen for managing muscle spasticity, particularly in neurological and musculoskeletal disorders.
Adult: Initial: 2 mg orally, 3 times daily. May be increased gradually in 2-4 mg increments at intervals of 1-4 days. Effective dose range: 6-24 mg/day in 3-4 divided doses. Single doses should not exceed 12 mg.
Note: Administer with or without food, but consistency is key. Taking with food increases sedation and dizziness. Tablets should be swallowed whole with a glass of water. Avoid abrupt discontinuation; taper dose to prevent rebound hypertension, tachycardia, and hypertonia.
Tizanidine is a centrally acting alpha-2 adrenergic receptor agonist. Its primary site of action is the spinal cord, where it inhibits the release of excitatory neurotransmitters (like glutamate and aspartate) from presynaptic terminals of spinal interneurons. This action enhances presynaptic inhibition, leading to a reduction in the facilitation of spinal motor neurons, thereby decreasing tonic stretch reflexes and muscle spasticity without directly affecting neuromuscular junction or muscle contractility.
Pregnancy: Category C: Animal studies have shown adverse effects. No adequate and well-controlled studies in pregnant women. Use only if potential benefit justifies potential risk to the fetus. Should not be used for routine labor or delivery.
Driving: NOT ADVISABLE, especially during initiation and dose titration. Causes drowsiness, dizziness, and blurred vision which impair driving ability and operation of machinery.
| Fluvoxamine | Markedly increases tizanidine AUC (up to 33-fold), leading to severe hypotension and sedation. | Contraindicated |
| Ciprofloxacin | Increases tizanidine AUC by 10-fold, increasing risk of adverse effects. | Contraindicated |
| Other CYP1A2 Inhibitors (e.g., oral contraceptives, cimetidine, mexiletine) | Moderate increase in tizanidine levels. Dose reduction of tizanidine needed. | Major |
| Alcohol and other CNS Depressants (Benzodiazepines, Opioids) | Additive CNS depression, impaired alertness, and respiratory depression. | Major |
| Antihypertensives (Beta-blockers, ACE inhibitors, Diuretics) | Potentiates hypotensive effect. | Moderate |
| Acetaminophen (Paracetamol) | May delay tizanidine absorption (Tmax increased). Clinical significance minimal. | Minor |