THERAPEUTICS

Brands

• Rimabotulinumtoxin B (Myobloc, Neurobloc)

Generic?

• No

Class

• Neurotoxin

Commonly Prescribed for

(FDA approved in bold)

• Cervical dystonia (CD)

• Glabellar lines

• Axillary hyperhidrosis

• Strabismus and blepharospasm associated with dystonia

• Hemifacial spasm

• Spasmodic torticollis

• Spasmodic dysphonia (laryngeal dystonia)

• Writer's cramp and other task-specific dystonias

• Spasticity associated with stroke

• Dynamic muscle contracture in cerebral palsy

• Sialorrhea (drooling)

• Headache

• Myofascial pain

How the Drug Works

• Blocks neuromuscular transmission by cleaving the vesicle-associated membrane protein (VAMP; synaptobrevin), which inhibits the vesicular release of acetylcholine from nerve terminals

• In CD and other dystonias, produces partial denervation of muscle and localized reduction in muscle activity. In hyperhidrosis, produces chemical denervation of sweat glands

• Also appears to inhibit release of neurotransmitters involved in pain transmission (including glutamate, calcitonin gene-related peptide, and substance P) and may enter CNS via retrograde axonal transport

How Long Until It Works

• Usually 1–3 days with peak effect beginning at 2 weeks

If It Works

• Continue to use as long as effective, but monitor for clinical effects

If It Doesn't Work

• Increase dose or change injection technique. Some pain disorders may respond better to oral medications

Best Augmenting Combos for Partial Response or Treatment-Resistance

• Increase dose or number of injections or change site of location

Tests

• None

ADVERSE EFFECTS (AEs)

How the Drug Causes AEs

• Most AEs are related to muscle weakness adjacent to the site of injection. Serious systemic AEs are rare, but injectors should use the lowest dose and be familiar with injection technique to minimize AEs

Notable AEs

• Injection site pain and hemorrhage, dry mouth, infection, fever, headache, pruritus, and myalgia. Most AEs depend on site of injection

• CD: dysphagia, neck weakness, upper respiratory infection

• Spasmodic dysphonia: hypophonia (“breathy” voice)