Zanaflex (Tizanidine) 2 mg and 4 mg Tablets and Capsules: Prescription Central Alpha-2 Agonist for Spasticity in MS and Spinal Cord Injury — Short Duration, Different Bioavailability Between Tablet and Capsule Forms

Information last reviewed: May 2026 — for educational purposes only.

Zanaflex (tizanidine hydrochloride) is a prescription short-acting alpha-2 adrenergic agonist used to manage spasticity — abnormal muscle tightness and involuntary spasms — associated with neurological conditions including multiple sclerosis (MS), spinal cord injury, and cerebrovascular disease. Unlike the antispasmodic agents used for acute musculoskeletal pain, tizanidine acts by a distinct mechanism and is specifically intended for pathological spasticity of upper motor neurone origin. It is also used off-label for acute low back spasm and tension headache. Available as tablets and capsules in 2 mg and 4 mg strengths.

What Is Tizanidine?

Tizanidine works by activating alpha-2 adrenergic receptors in the spinal cord, which inhibits presynaptic motor neurones and reduces the facilitation of spinal reflexes. The result is reduced muscle tone and less frequent spasms. Its mechanism is similar to clonidine (another alpha-2 agonist used for hypertension), explaining why tizanidine can lower blood pressure — particularly hypotension on standing (orthostatic hypotension) — which is an important side effect to monitor.

Tizanidine is notable for causing less muscle weakness compared to baclofen at equivalent antispastic doses, which can be clinically important for patients who need to retain some muscle strength for functional activities (walking, transfers). Its short half-life (~2–2.5 hours) means its effect is relatively brief, allowing patients to time doses for periods of peak spasticity (e.g., evening or bedtime) while maintaining acceptable muscle function at other times.

Prescription Status

Tizanidine is prescription-only in the United States. There is no OTC version. It must be used under physician supervision with monitoring of liver function tests (LFTs), as rare cases of liver injury (hepatotoxicity) have occurred — particularly in the first 6 months of therapy. Baseline LFTs are recommended before starting, with monitoring at 1, 3, and 6 months.

Strengths, Forms, and Dosing

• 2 mg tablets — starting dose; typical initial dose 2–4 mg every 6–8 hours as needed for spasticity; can be titrated upward every 1–4 days
• 4 mg tablets — maintenance and dose-escalation tablet; max single dose 16 mg; max 36 mg/day in divided doses; no more than 3 doses per day
• 2 mg and 4 mg capsules — extended formulation option; capsules can be opened and sprinkled on food; note: bioavailability differs between tablet and capsule taken fasted vs. with food — switching between formulations or food states requires dose re-evaluation

Important formulation note: Tizanidine tablets and capsules have different pharmacokinetic profiles when taken with or without food. The tablet taken with food increases Tmax and peak plasma concentration significantly more than the capsule with food. Prescribers should specify one formulation and consistent relation to food intake. Patients should not switch between tablets and capsules without medical guidance.

Price of Generic Tizanidine

Generic tizanidine is available in both tablet and capsule forms and is inexpensive at US pharmacies. A 90-tablet supply of 4 mg tablets is available at low cost with or without insurance. Both formulations (tablets and capsules) are available as generics following Zanaflex's patent expiry.

Frequently Asked Questions

Can I take tizanidine with blood pressure medication?

Use with caution. Tizanidine lowers blood pressure through its alpha-2 agonist mechanism, and combining it with antihypertensive medications can cause additive hypotension and risk of fainting. It should not be combined with fluvoxamine or ciprofloxacin — both inhibit CYP1A2, the enzyme that metabolises tizanidine — as this causes dramatic increases in tizanidine plasma levels and risk of severe hypotension and sedation.

Is tizanidine better than baclofen for spasticity?

Both are effective first-line antispastics for MS and spinal cord injury spasticity. Baclofen (a GABA-B agonist) tends to have longer duration of action and is more commonly used when consistent round-the-clock spasm control is needed. Tizanidine's shorter duration is an advantage when targeted, time-limited control is preferred. Choice depends on patient-specific response, side-effect tolerance, and whether consistent or intermittent antispastic control is required.

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