Capsaicin cream: topical pain relief for osteoarthritis

The UK product information for Zacin 0.025% cream states that it is indicated for the symptomatic relief of pain associated with osteoarthritis. It is a counter-irritant type of treatment: the precise mechanism is not fully understood, but evidence suggests that capsaicin depletes and prevents the reaccumulation of substance P in peripheral sensory neurons, a chemical involved in transmitting pain signals.

That mechanism explains the pattern people notice. It does not reduce swelling like an NSAID gel, and the benefit builds gradually with regular use rather than appearing within minutes.

Apply only a small, pea-sized amount of cream to unbroken skin over the affected area four times daily, evenly spaced through the waking hours and not more often than every 4 hours. Rub it in gently until there is no residue left on the surface. The cream is not suitable for use in children.

Wash your hands immediately after application unless the hands are the area being treated, and do not apply near the eyes. Tight bandages should not be applied on top of the cream.

• Avoid a hot bath or shower just before or after applying it, as this can enhance the burning sensation.

• Avoid inhaling vapours from the cream, which can irritate the eyes and airways.

• Do not use more often than four times a day or in larger amounts, as that makes burning more likely.

Transient burning on application is expected and is more frequent when applications exceed four times daily, when too much is used, and when applied just before or after a bath or shower. Pain relief usually starts within the first week and increases with continued regular application over the following two to eight weeks, so judging it after a day or two is not meaningful.

Seek medical advice if the condition worsens, or clears up and then recurs.

Skin irritation or transient burning is the main effect. Rarely, irritation of the mucous membranes of the eyes and airways, with coughing, sneezing and runny eyes, has been reported, and there have been a few reports of breathlessness, wheezing and exacerbation of asthma, so people with asthma should take extra care with vapours. Benzyl alcohol and cetyl alcohol in the cream may cause mild local irritation or contact dermatitis.

It is contraindicated on broken or irritated skin and in people with hypersensitivity to capsaicin or any ingredient.

The safety of this cream during pregnancy and lactation has not been established in humans or animals. However, because only small amounts are absorbed through the skin, the product information considers it unlikely that capsaicin will cause adverse effects in humans. Speak to a pharmacist or doctor before using it if you are pregnant or breastfeeding.

No interaction studies have been performed. If you use other creams or gels on the same joint, ask a pharmacist how to combine them.

Osteoarthritis pain is usually managed with exercise, weight management where relevant, simple painkillers and topical NSAIDs, with oral medicines and joint injections considered if pain persists. Capsaicin is one topical option among these, and the choice depends on the joint, skin and personal preference. Persistent or worsening pain, night pain, a hot swollen joint or a joint that locks should be assessed.