Metronidazole in conjunction with penicillin neither prevents recurrence nor enhances recovery from peritonsillar abscess when compared with penicillin alone: a prospective, double-blind, randomized, placebo-controlled trial.

The objectives of this study were to evaluate the efficacy of metronidazole in conjunction with penicillin in preventing the recurrence of peritonsillar abscess (PTA) and to learn whether metronidazole enhances the recovery from PTA when compared with penicillin alone.

In this prospective, double-blind, randomized, placebo-controlled trial, 200 adult outpatients with PTA at our ear, nose and throat emergency department received either penicillin (1 000 000IU) × 3 and metronidazole (400 mg) × 3 for 10 and 7 days orally (combination group, N = 100) or penicillin and placebo (penicillin group, N = 100) after incision and drainage of the PTA. Afterwards they received a symptom questionnaire via e-mail daily for 2 weeks, then weekly for 6 weeks. The primary outcome was efficacy of metronidazole in conjunction with penicillin in preventing PTA recurrence in 56 days; the secondary outcome was ability of metronidazole plus penicillin to enhance recovery from PTA in 28 days. All healthcare contacts were registered during follow-up. Registered on www.clinicaltrials.gov with the identifier NCT01255670.

Of the 200 patients, 20 returned to hospital with recurrent symptoms, 10 in each group (P = 1.00). In the combination group, the mean (SD) duration of throat-related symptoms was 5.6 (5.0) days and in the penicillin group it was 5.3 (2.7) days, values for fever were 1.5 (0.9) and 1.6 (1.0) days, respectively, and those for poor overall physical condition were 4.0 (3.9) and 4.5 (4.9) days; there were no significant differences between groups. The adverse effects nausea and diarrhoea lasted longer in the combination group (P = 0.01).

For healthy adult PTA patients treated with incision and drainage, metronidazole neither prevents recurrence nor enhances recovery when combined with penicillin compared with penicillin alone, but instead leads to increased adverse effects.