CapsaicinRx

Trade Names: Zostrix and many others

Drug Class: Topical analgesic

Preparations
Cream: 0.025% (45- and 90-g tube); 0.075% (30- and 60-g tube)
Gel: 0.025% (15 and 30 g)
Lotion: 0.025% (59 mL), 0.075% (59 mL)
Roll-on: 0.075% (60 mL)

Dose: Apply to affected area three to four times daily. Less frequent application is less effective.

Indications: Postherpetic neuralgia, RA, osteoarthritis, diabetic neuropathy, chronic neuralgic pain

Mechanism of Action: Depletes peripheral sensory neurons of substance P, a mediator of pain.

Contraindications: Hypersensitivity to capsaicin

Precautions: Avoid contact with eyes, mucous membranes, genitalia, or open wounds. Wash hands immediately after applying.

Pregnancy Risk: C

Adverse Effects
Common: Transient sensation of burning when first applied that diminishes with use
Less common: Erythema

Drug Interactions: None

Patient Instructions: For external use only. Do not apply to broken skin. Wash hands after use or use gloves. Avoid contact with eyes. Regular use is required for effect. Effect is slow; clinical benefits may take weeks or months. There is a transient sensation of burning when first applied.

Comments: The transient burning that occurs in most patients initially has made it difficult to perform true double-blind studies to assess efficacy. In practice, few patients derive clinically useful benefit from capsaicin in the treatment of pain from arthritis. Most suitable are patients with a few affected joints. The requirement for regular and frequent application and the slow onset of action over several weeks are disadvantages.

Clinical Pharmacology: Not known

Cost: $