Tizanidine

CLINICAL USE

Spasticity associated with multiple sclerosis or spinal cord injury/disease

DOSE IN NORMAL RENAL FUNCTION

2–24 mg daily in up to 3–4 divided doses (depending on response)

PHARMACOKINETICS

Molecular weight : 290.2 (as hydrochloride)

%Protein binding : 30

%Excreted unchanged in urine : <11

Volume of distribution (L/kg) : 2.4

half-life – normal/ESRD (hrs) : 2–4/Increased

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

25–50 Dose as in normal renal function <25 Initial dose 2 mg once daily and slowly increase by 2 mg increments. Increase daily dose before increasing frequency of administration

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD : Unknown dialysability. Dose as in GFR<25 mL/min

HD : Unknown dialysability. Dose as in GFR<25 mL/min

HDF/high flux : Unknown dialysability. Dose as in GFR<25 mL/min

CAV/VVHD : Unknown dialysability. Dose as in GFR=25–50 mL/min

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugs

Anti-arrhythmics: enhanced muscle relaxant effect with procainamide

Antibacterials: concentration increased by ciprofloxacin – avoid concomitant use Antihypertensives: enhanced hypotensive effect Oral contraceptives: clearance of tizanidine reduced by 50%

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

–

Comments

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OTHER INFORMATION

Pharmacokinetic data suggest that renal clearance in the elderly may be decreased by up to 3-fold May induce hypotension; therefore may potentiate the effect of antihypertensive drugs, including diuretics – exercise caution With beta-blockers or digoxin, may potentiate hypotension or bradycardia LFTs should be monitored monthly for the first 4 months Tizanidine undergoes rapid and extensive first pass metabolism. The metabolites (mainly inactive) constitute 70% of the administered dose and are excreted via the renal route

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