Can tizanidine (a muscle relaxant) cause sleepiness, especially in patients with a history of sleep disorders, such as insomnia or sleep apnea?

Does Tizanidine Cause Sleepiness?

Yes, tizanidine causes significant sedation and drowsiness in approximately 48% of patients, with 10% experiencing severe sedation—this is a dose-related effect that peaks within 1.5 hours of dosing and is one of the most common adverse effects of this medication. 1

Mechanism and Frequency of Sedation

Tizanidine is a centrally acting alpha-2 adrenergic receptor agonist that produces sedation through its action on the central nervous system. 1, 2

Key sedation statistics:

• 48% of patients report sedation at any dose 1
• 92% of patients receiving 16 mg reported drowsiness during a 6-hour study period 1
• 76% experienced drowsiness at 8 mg doses 1
• Sedation typically begins 30 minutes after dosing and peaks at 1.5 hours 1
• 51% of patients on 16 mg continued to report drowsiness 6 hours post-dose 1

Clinical Implications for Patients with Sleep Disorders

For patients with insomnia or sleep disturbances, tizanidine's sedative properties can actually be therapeutically beneficial when dosed strategically. 3, 4

• In spastic quadriplegic children with severe refractory sleep disturbances, tizanidine (0.1-0.2 mg/kg/day) improved sleep induction and/or maintenance in 61.9% of patients 3
• When taken at bedtime, patients report improved sleep onset with minimal "hangover sensation" upon waking 4
• The sedation effect is most pronounced during the first week of titration, then stabilizes during maintenance therapy 1

For patients with sleep apnea, extreme caution is warranted. The American Academy of Sleep Medicine guidelines emphasize that sedating medications should be used cautiously in patients with compromised respiratory function, including sleep apnea. 5 Tizanidine's sedative effects could potentially worsen respiratory depression during sleep in these patients.

Dosing Strategy to Minimize Daytime Sedation

Start with bedtime-only dosing during initial titration to allow sedation to occur during sleep hours. 6

• Begin at 2 mg at bedtime 6, 7
• Titrate gradually over 2-4 weeks based on response and tolerability 2
• Older adults rarely tolerate doses above 30-40 mg/day 6, 7
• If daytime dosing is required, restrict administration to bedtime initially to assess tolerance 3

Critical Safety Warnings

Sedation may interfere with everyday activities and increases fall risk, particularly in older adults. 5, 1

Avoid combining tizanidine with other CNS depressants (benzodiazepines, opioids, antipsychotics, sedating antidepressants) as this produces additive sedative effects and increases risk of excessive sedation. 6 When combined with oxycodone specifically, there is a 2.44-fold increase in CNS adverse events including sedation. 7

Never abruptly discontinue tizanidine in long-term users—taper slowly to avoid withdrawal symptoms including rebound hypertension, tachycardia, and anxiety. 6, 1, 8

Comparative Tolerability

Drowsiness/somnolence is the most common adverse effect alongside dry mouth. 2 However, tizanidine causes less subjective muscle weakness compared to baclofen or diazepam, making it preferable when muscle strength preservation is important. 2 Global tolerability was rated good-to-excellent in 44-100% of tizanidine recipients versus 20-54% for diazepam recipients. 2

Monitoring Recommendations

• Assess sedation severity at each dose adjustment 1
• Monitor for orthostatic hypotension, which can accompany sedation 6
• Evaluate impact on daily functioning and fall risk, especially in elderly patients 5, 6
• Consider polysomnography if sleep-disordered breathing is suspected before initiating therapy 5