Appropriate Dosage of Zanaflex (Tizanidine) for a 46-Year-Old Patient with Multiple Sclerosis
For a 46-year-old patient with multiple sclerosis, the appropriate starting dose of tizanidine (Zanaflex) is 2-4 mg, which can be gradually increased to an optimal dose, with a maximum of 36 mg daily divided into three doses.
Initial Dosing Recommendations
- Start with 2-4 mg per dose, as the dose-related nature of tizanidine's common adverse events makes it prudent to begin treatment with lower doses 1
- Doses can be repeated at 6 to 8 hour intervals, as needed, up to a maximum of three doses in 24 hours 1
- Effects peak at approximately 1-2 hours after administration and typically last 3-6 hours 1
Titration Schedule
- Increase the dose gradually in 2-4 mg increments to achieve optimal effect (satisfactory reduction of muscle tone at a tolerated dose) 1
- Titration should occur over 2-4 weeks to find the optimal dosage for each patient, as there is wide interpatient variability in effective plasma concentrations 2
- The total daily dose should not exceed 36 mg 1
Dosing Considerations for MS Patients
- Clinical studies have demonstrated efficacy of tizanidine specifically in multiple sclerosis patients with spasticity 3, 4
- In MS patients, tizanidine has shown a 20-37% reduction in mean muscle tone scores compared to placebo 2, 5
- Improvement in muscle tone occurred in 60-82% of tizanidine recipients in clinical trials 2
Monitoring and Side Effects
- Monitor for common side effects including dry mouth and somnolence/drowsiness, which are the most frequently reported adverse effects 2, 6
- Unlike some other muscle relaxants, tizanidine appears less likely to cause subjective muscle weakness, which is an advantage in MS patients 2
- Two patients in clinical trials developed elevated liver function tests that decreased with cessation of therapy, so liver function monitoring may be appropriate 3
Important Administration Considerations
- Food has complex effects on tizanidine pharmacokinetics, which may result in clinically significant differences when switching administration between fed and fasted states 1
- For consistency, advise the patient to take tizanidine either always with food or always without food 1
- Experience with single doses exceeding 8 mg and daily doses exceeding 24 mg is limited, so caution is advised when approaching higher doses 1
Comparative Efficacy
- Tizanidine has similar efficacy to baclofen in treating spasticity in MS but with a more favorable tolerability profile 2, 4
- While drowsiness is a frequently reported adverse effect with both agents, subjective muscle weakness appears to be less of a problem with tizanidine than with baclofen 2
Remember that the maximum effect on spasticity typically occurs within 1 week of reaching an effective dose, and benefits may be maintained for at least 1 week after discontinuation of therapy 5.