Dapsone: what you need to know

Although dapsone was first synthesised in 1908, it was only in 1950, when being used under the mistaken impression that dermatitis herpetiformis (DH) is caused by a bacterial infection, that its remarkable efficacy in this disorder was discovered. Today, the licensed indications for dapsone are, in addition to DH, as part of the multidrug treatment of leprosy and in the prophylaxis of pneumocystis infection in patients with HIV. However, although dapsone is an antimicrobial, it is the drug’s rather poorly understood anti-inflammatory effects that have led to its use in a wide range of dermatoses. In some of the rarer conditions, the evidence of efficacy inevitably relies on case reports and anecdotes, rather than coming from controlled trials. It is not an uncommon experience in dermatology clinics, when faced with a difficult therapeutic problem in a patient with a chronic inflammatory disorder in which first- or second-line treatments have already been tried but have failed, to find that ‘a trial of dapsone’ is suggested. Many of the disorders dapsone is used to treat are chronic ones. So, although dapsone therapy is rarely likely to be initiated in primary care, GPs may, from time to time, encounter patients who are on the drug and be asked to participate in the monitoring or prescribing of it. For this reason, it is important for them to be aware of some of the important side-effects that may be encountered, especially as these can be a little unusual.