R180 Pill: What Is It?

Tizanidine hydrochloride 4 mg — a white, oval muscle relaxant prescribed for spasticity and muscle spasms. Generic Zanaflex by Actavis/Teva.

What Is the R180 Pill?

The white oval tablet imprinted R180 is tizanidine hydrochloride 4 mg, a generic form of Zanaflex manufactured by Actavis (now part of Teva Pharmaceuticals). It is a centrally acting skeletal muscle relaxant used to manage muscle spasticity — increased muscle tone and spasms caused by conditions affecting the central nervous system.

Tizanidine is a prescription medication. Unlike some other muscle relaxants, it works through a different mechanism — it is an alpha-2 adrenergic agonist, similar in some ways to clonidine, rather than acting directly on muscle tissue.

How to Identify the R180 Tablet Visually

• Color: White
• Shape: Oval (elliptical)
• Imprint: "R180" on one face; the reverse may be plain or scored
• Size: Approximately 10–11 mm in length
• Texture: Smooth, typically uncoated

If you are trying to confirm a pill's identity, a pharmacist is the appropriate professional to verify it. Do not take an unidentified medication.

What Is Tizanidine Used For?

Tizanidine is FDA-approved for the management of spasticity — a condition characterized by involuntary muscle stiffness and spasms. Conditions commonly treated with tizanidine include:

• Multiple sclerosis (MS) — spasticity is a common and disabling symptom of MS
• Spinal cord injury — trauma to the spinal cord frequently causes spasticity below the level of injury
• Stroke rehabilitation — spasticity can occur after a stroke and impair motor recovery
• Chronic back pain — prescribed off-label by some clinicians for muscle spasm associated with back and neck conditions

How Does Tizanidine Work?

Tizanidine is a central alpha-2 adrenergic receptor agonist. By stimulating alpha-2 receptors in the brain and spinal cord, it inhibits the release of excitatory neurotransmitters and reduces the transmission of nerve signals that cause muscle spasm. The result is decreased muscle tone and reduced frequency and severity of muscle spasms. Its mechanism makes it distinct from benzodiazepine muscle relaxants (which enhance GABA) and from direct-acting agents like dantrolene.

Side Effects and Warnings

• Sedation: Tizanidine causes significant drowsiness. This is one of its most common and pronounced side effects. Do not drive, operate heavy machinery, or perform activities requiring alertness while taking it.
• Low blood pressure (hypotension): Tizanidine can lower blood pressure, especially when standing up quickly (orthostatic hypotension). This can cause dizziness or fainting.
• Liver toxicity: Rare but serious liver injury has been reported. Liver function monitoring may be warranted with prolonged use.
• Alcohol and CNS depressants: Combining tizanidine with alcohol, benzodiazepines, or opioids can dangerously amplify sedation and blood pressure lowering effects.
• Ciprofloxacin and fluvoxamine: These medications significantly increase tizanidine blood levels and are contraindicated with tizanidine — the combination can cause severe hypotension and sedation.
• Abrupt discontinuation: Stopping tizanidine suddenly, especially after prolonged use, may cause rebound hypertension, tachycardia, and muscle spasm. Taper under medical guidance.

Tizanidine vs. Other Muscle Relaxants

Tizanidine is often compared to cyclobenzaprine (Flexeril) and baclofen, two other commonly prescribed muscle relaxants. Unlike cyclobenzaprine — which has significant anticholinergic effects and a long half-life — tizanidine has a shorter duration of action (typically 3–6 hours), making it easier to time doses around activities. Baclofen also reduces spasticity but acts on GABA-B receptors rather than alpha-2 receptors. A prescriber selects the most appropriate agent based on the patient's specific condition, other medications, and individual response.

Frequently Asked Questions