tizanidine hydrochloride: clinical use

Prescribing considerations

• Tizanidine has a narrow therapeutic index and substantial inter-patient pharmacokinetic variability.
• Avoid abrupt withdrawal because rebound hypertension, tachycardia and increased muscle tone can occur.
• Use caution in older adults and in cardiovascular, renal or mild-to-moderate hepatic impairment.
• Sedation, orthostatic hypotension and syncope can impair everyday activities.
• Safety and efficacy are not established in people under 18 years.

Contraindications and cautions

• Hypersensitivity to tizanidine or an excipient.
• Severe hepatic impairment.
• Concurrent ciprofloxacin, fluvoxamine or another potent CYP1A2 inhibitor.
• Relevant hereditary intolerance or malabsorption involving lactose or sucrose in the selected product.

Monitoring

• Assess blood pressure, pulse, sedation and orthostatic symptoms.
• Monitor liver function where clinically indicated, particularly with increased exposure or symptoms suggesting hepatic dysfunction.
• Monitor renal function and adverse effects closely in significant renal impairment.
• Consider clinical laboratory and ECG monitoring in cardiovascular, hepatic or renal disease.
• Review smoking changes because smoking can reduce tizanidine concentrations.

Clinical pharmacology

Tizanidine is a centrally acting alpha-2 adrenergic agonist. It is rapidly absorbed, undergoes extensive hepatic first-pass metabolism mainly through CYP1A2, and its inactive metabolites are predominantly eliminated through the kidneys.

Formulation and product differences

• The selected product comprises two scored tablet strengths.
• The lower-strength tablet can be divided into equal halves; the higher-strength tablet is cross-scored and can be divided into equal halves or quarters.
• Both formulations contain lactose monohydrate and sucrose.

Tablet

Route: Oral

Strengths: 2 mg, 4 mg