What is the efficacy of Tizanidine (muscle relaxant) and Gabapentin (anticonvulsant) for temporary jaw tics?

Efficacy of Tizanidine and Gabapentin for Temporary Jaw Tics

Tizanidine shows better efficacy for temporary jaw tics compared to gabapentin, with evidence supporting its use as a centrally acting muscle relaxant specifically for jaw-related muscle spasms.

Mechanism of Action and Efficacy

Tizanidine

• Acts as an α2-adrenergic receptor agonist with centrally acting spasmolytic properties 1
• Effectively reduces muscle spasticity and pain without loss of motor strength 1, 2
• Shows improvement in spasticity by:
  • Reinforcing presynaptic inhibition
  • Enhancing postsynaptic inhibition (both Ia reciprocal and Ib nonreciprocal)
  • Reducing flexor reflexes 3
• Demonstrated quick pain relief in muscle spasm conditions (initial relief by day 2 of treatment, complete relief after 4 days) 4
• Specifically effective for myofascial pain of masticatory muscles with 53.8% of patients showing complete resolution of symptoms after 2 weeks of treatment 5

Gabapentin

• Binds to voltage-gated calcium channels at the α-δ subunit to inhibit neurotransmitter release 6
• More commonly used for neuropathic pain conditions rather than muscle spasms 6
• Limited evidence for efficacy in facial spasm conditions, with one small study showing 69.6% efficacy in hemifacial spasm 7
• Not specifically studied or recommended for jaw tics in current guidelines

Dosing Recommendations

Tizanidine

• Start at a low dose of 2-4 mg
• Typical effective dosing: 4 mg three times daily 1, 2
• Can be increased gradually in 2-4 mg steps to optimum effect
• Maximum daily dose should not exceed 36 mg 2
• For myofascial face pain specifically, 4 mg/day (2 mg twice daily) has shown efficacy 5

Gabapentin (if considered as alternative)

• Starting dose of 100-300 mg at bedtime or 100-300 mg three times daily
• Requires gradual titration of 100-300 mg every 1-7 days as tolerated
• Effective doses typically range from 300-600 mg/day for neuropathic pain 6

Important Considerations and Precautions

Tizanidine

• Adverse effects include dose-dependent sedation, drowsiness, dizziness, and dry mouth 6
• Contraindicated with CYP1A2 inhibitors (ciprofloxacin, fluvoxamine) 6
• Use with caution in patients with:
  • Hepatic or renal dysfunction
  • Cardiac conditions
  • Elderly patients (start at lower doses) 1
• Should be tapered slowly if discontinuing after long-term use to prevent withdrawal symptoms 6

Gabapentin

• Common side effects include dizziness, somnolence, peripheral edema, and weight gain 6
• Requires dosage reduction in patients with renal insufficiency 6
• Less specific for muscle spasm conditions compared to tizanidine

Treatment Algorithm for Jaw Tics

1. First-line approach: Tizanidine 2 mg twice daily for 2 weeks 5

   • If partial response: Increase to 4 mg three times daily
   • If good response: Continue for 2-4 weeks then reassess

2. Alternative approach (if tizanidine is contraindicated or poorly tolerated):

   • Consider gabapentin starting at 100-300 mg at bedtime, increasing to 300-600 mg/day in divided doses 6

3. For refractory cases:

   • Consider combination therapy or referral to specialist for evaluation for other interventions such as botulinum toxin injections 6

Monitoring

• Assess response after 2 weeks of treatment
• Monitor for side effects, particularly sedation and dizziness
• If using long-term, periodic evaluation of liver function with tizanidine is recommended

Tizanidine has demonstrated specific efficacy for myofascial pain of the jaw muscles and represents the preferred pharmacological option for temporary jaw tics based on the available evidence.