What Is Myobloc? Uses, Dosage, and What You Need to Know in 2026

Myobloc is a prescription injectable medication that belongs to a category of drugs called botulinum neurotoxins. It's not Botox — it's the only FDA-approved botulinum toxin type B product in the United States, and it treats conditions that most people haven't heard of. Here's everything you need to know.

The Basics: What Is Myobloc?

Myobloc is the brand name for rimabotulinumtoxinB, a purified form of botulinum toxin type B produced by the bacterium Clostridium botulinum. It's manufactured by Solstice Neurosciences, a subsidiary of Supernus Pharmaceuticals, and administered as an injection by a trained healthcare provider.

Like all botulinum toxins, Myobloc works by blocking the release of acetylcholine at nerve-muscle junctions, causing temporary muscle relaxation or reducing glandular secretion depending on the target. It was first approved by the FDA in December 2000 for cervical dystonia — making it the first botulinum toxin type B product to receive FDA approval, and at the time, the first neurotoxin approved for cervical dystonia in adults.

What Is Myobloc Approved to Treat?

Myobloc has two FDA-approved indications, both in adults:

Cervical dystonia (spasmodic torticollis) — A neurological movement disorder characterized by involuntary contractions of the neck muscles, causing the head to twist, turn, or be pulled forward or backward in abnormal positions. It's painful and often significantly impairs quality of life. Myobloc relaxes the overactive neck muscles to reduce abnormal head positioning and pain.

Chronic sialorrhea (excessive drooling) — Added in August 2019. Sialorrhea is chronic, troublesome drooling that can occur in adults with Parkinson's disease, ALS, stroke, or other neurological conditions. Myobloc is injected into the salivary glands to reduce excess saliva production.

Who Is Myobloc For?

Myobloc is specifically indicated for adults. It's particularly valuable for a subset of patients with cervical dystonia who have:

Developed immunoresistance (blocking antibodies) to botulinum toxin type A products (Botox, Dysport, Xeomin)

Had an inadequate response to type A toxins despite optimized dosing

Had intolerance to type A formulations

Because it cleaves a different protein (VAMP/synaptobrevin) than type A toxins (which cleave SNAP-25), Myobloc can work even when type A toxins no longer do.

How Is Myobloc Given? Dosage and Administration

Myobloc is given as an injection by a healthcare provider — you cannot self-administer it at home. Here's how it's used for each indication:

For cervical dystonia: The initial recommended dose is 2,500–5,000 units, divided among the affected neck muscles, for patients who have previously tolerated botulinum toxin injections. Toxin-naive patients start lower. Most treatment sessions involve ≤12,500 units total. Effects last approximately 3–4 months. Repeat injections are typically given every 12 weeks.

For chronic sialorrhea: 2,500 or 3,500 units are injected intraglandularly into the parotid and submandibular glands.

Myobloc is available in three vial sizes: 2,500 units/0.5 mL, 5,000 units/1 mL, and 10,000 units/2 mL. Unlike type A botulinum toxins, it does not require reconstitution — it comes as a ready-to-use liquid. Must be stored refrigerated at 36°F–46°F; do not freeze or shake.

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What Are the Side Effects?

Common side effects include dry mouth (up to 39% of patients), difficulty swallowing (dysphagia, up to 25%), injection site pain, and headache. Myobloc carries an FDA boxed warning about the risk of toxin spreading beyond the injection site, potentially causing botulism-like symptoms including difficulty breathing and swallowing — which can be life-threatening.

Is Myobloc the Same as Botox?

No. Botox contains onabotulinumtoxinA — a type A botulinum toxin. Myobloc contains rimabotulinumtoxinB — a type B toxin. They work similarly (both block nerve-muscle communication) but cleave different proteins, are produced from different bacterial strains, come in different formulations, and use completely different dosing units. They are not interchangeable.

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Is Myobloc a Controlled Substance?

No. Myobloc is not a controlled substance. It is a prescription-only medication (Schedule not applicable), but it does not have the DEA scheduling restrictions associated with opioids, benzodiazepines, or stimulants. You do need a valid prescription from a licensed healthcare provider to obtain it.

For a deeper dive into how Myobloc works at the cellular level, see: How Does Myobloc Work?. And if you're having trouble finding it at a pharmacy, medfinder calls local pharmacies and texts you which ones have it in stock.