The PATCH 1 study involved 274 patients and tested whether low-dose penicillin (250mg) twice a day for 12 months could prevent further occurrences in patients who had experienced at least two episodes of leg cellulitis in the past three years.
Subjects remained in the trial for up to three years to see whether the penicillin was effective only while it was being taken, or whether there were longer-term benefits after the antibiotics had been stopped.
Subjects in the penicillin group were less likely to have another episode of cellulitis compared with the placebo group (22% compared with 37%). However, this protection was gradually lost after patients stopped taking the medication at 12 months. By three years, approximately half of all patients in both groups had experienced at least one further episode.
These outcomes emphasise that prophylactic penicillin 250mg twice daily is useful to prevent future recurrences of leg cellulitis if patients have had more than one episode and are especially at risk because of obesity, diabetes, lymphoedema and pre-existing skin conditions on their feet.
Thomas KS, Crook AM, Nunn AJ et al N Engl J Med 2013; 368: 1695-1703