What is the starting dose of tizanidine (Zanaflex) for adults?

Starting Dose of Tizanidine for Adults

The recommended starting dose of tizanidine for adults is 2-4 mg orally, which can be repeated at 6-8 hour intervals as needed, with gradual titration to optimal effect. 1

Dosing Protocol

Tizanidine is a centrally-acting alpha-2 adrenergic agonist used as a muscle relaxant for the treatment of spasticity. When initiating therapy, follow this protocol:

1. Initial dose:

   • Start with 2-4 mg orally 1
   • Lower starting doses help minimize common side effects

2. Dosing frequency:

   • Can be repeated every 6-8 hours as needed
   • Maximum of three doses in 24 hours 1

3. Titration:

   • Increase gradually in 2-4 mg increments 1
   • Titrate over 2-4 weeks to find optimal dose for each patient 2
   • Aim for satisfactory reduction of muscle tone at a tolerated dose

4. Maximum dosing:

   • Daily maximum: 36 mg total 1
   • Single dose maximum: 8 mg (though doses up to 12 mg have been used) 1

Pharmacokinetics

• Peak effect occurs at 1-2 hours after administration
• Effects typically last 3-6 hours 1
• Food has complex effects on tizanidine pharmacokinetics that may affect onset of action and adverse events 1

Clinical Considerations

Indications

Tizanidine is particularly effective for:

• Spasticity associated with cerebral or spinal disorders 2
• Chronic stroke patients with spasticity 3
• Back pain with muscle spasm 4

Side Effects to Monitor

• Most common: dry mouth and somnolence/drowsiness 2
• Less common than with other muscle relaxants: subjective muscle weakness 2
• Potential for hypotension, especially when starting therapy 3

Important Precautions

• When prescribed with methadone, there is increased risk of prolonged QTc interval 3
• Use caution with CYP1A2 inhibitors (e.g., oral contraceptives) 3
• Dose reduction recommended for hepatic and renal impairment 3

Clinical Pearl

Unlike diazepam and other benzodiazepines (which should be avoided during stroke recovery due to potential deleterious effects on recovery), tizanidine has been shown to improve spasticity and pain without significant loss of motor strength in chronic stroke patients 3.

Monitoring

Monitor for sedation, hypotension, dry mouth, asthenia, and dizziness, especially during the initial titration period 3. If these side effects occur, consider reducing the dose or extending the interval between doses.

Tizanidine's favorable side effect profile compared to other antispasmodics makes it an attractive option for treating spasticity, but careful dose titration is essential to maximize benefits while minimizing adverse effects.