What is the recommended dosing of tizanidine (Zanaflex) for back spasm?

Tizanidine Dosing for Back Spasm

The recommended dosing of tizanidine (Zanaflex) for back spasm is to start with 2-4 mg orally every 6-8 hours as needed, with gradual titration in 2-4 mg increments to achieve optimal effect, not exceeding 36 mg per day. 1

Initial Dosing

• Start with 4 mg as a single dose
• Effects peak at 1-2 hours and last 3-6 hours 1
• Can be repeated at 6-8 hour intervals as needed
• Maximum of 3 doses in 24 hours

Titration Strategy

• Increase gradually in 2-4 mg steps to achieve optimal effect 1
• Titrate over 2-4 weeks to find the effective dose for each patient 2
• Effective dosages typically range from 2-36 mg/day 2

Maximum Dosing

• Total daily dose should not exceed 36 mg 1
• Limited clinical experience with single doses exceeding 8 mg
• Limited experience with daily doses exceeding 24 mg

Administration Considerations

• Food has complex effects on tizanidine pharmacokinetics
• Taking with or without food can significantly affect drug levels and side effects 1
• Be consistent with administration (either always with food or always without)

Clinical Efficacy

• Tizanidine reduces muscle tone for several hours after a single dose 1
• Provides quick pain relief in back pain with muscle spasm (initial relief typically by day 2 of treatment) 3
• Complete pain relief often achieved after approximately 4 days of treatment 3

Important Monitoring

• Monitor for hypotension, especially during initial titration
  • Two-thirds of patients on 8 mg doses experience 20% reduction in blood pressure 1
  • Blood pressure reduction peaks 2-3 hours after dosing
• Monitor liver function tests during the first 6 months of treatment 1
  • Approximately 5% of patients may develop elevated liver enzymes

Cautions and Contraindications

• Use with caution in patients receiving concurrent antihypertensive therapy
• Avoid use with other α2-adrenergic agonists
• Contraindicated with CYP1A2 inhibitors (ciprofloxacin, fluvoxamine)
• Use caution with other CYP1A2 inhibitors (oral contraceptives, amiodarone, verapamil, etc.) 4
• Avoid in patients with hepatic or renal dysfunction 4
• Use caution in elderly patients due to sedative and hypotensive effects 4

Perioperative Management

• Can be continued preoperatively including the day of surgical procedure 4
• May provide benefits including improved postoperative pain control and decreased opioid consumption 4

Common Side Effects

• Dry mouth and somnolence/drowsiness are most common 2
• Sedation occurs in approximately 22% of patients 5
• Less likely to cause subjective muscle weakness compared to baclofen or diazepam 2

Discontinuation

• If used long-term, taper slowly to avoid withdrawal symptoms
• Abrupt discontinuation may cause rebound hypertension, tachycardia, and hypertonia 4

Tizanidine is an effective option for back spasm with a favorable tolerability profile compared to other muscle relaxants. The ability to titrate the dose allows for optimization of efficacy while minimizing side effects.