Objectives To explore the relative effectiveness of topical or oral metronidazole used for malodour in necrotic cancers and to propose a protocol for metronidazole usage in managing malodour.

Methods A retrospective case note review of the management of malodour over 10 years comparing outcomes with topical, intermittent and maintenance oral metronidazole.

Results Among 179 patients treated for malodour, the commonest primaries were cervical (45%), and head and neck cancers (40%). Outcomes were poor during the period when only topical or intermittent oral metronidazole was used. Topical use gradually decreased (97% vs 55%) and the proportion of patients receiving maintenance oral metronidazole increased (0% in 2003–2004 vs 93% in 2011). Concurrently, there was reduction in documented malodour (12.5% of visits per patient in 2003–2004 vs 1.5% in 2011, p<0.01).

Conclusions Our data support formulary guidelines recommending maintenance metronidazole for recurrent malodour. Dimethyl trisulfide, a product of anaerobic necrosis causes malodour and can attract maggot-producing flies to decaying tissues. Therefore, to reduce anaerobic malodour in vulnerable settings, we propose a ladder for metronidazole titration. High-risk patients should start with 400 mg thrice daily ×7 days and continue 200 mg once daily. The SNIFFF severity (Smell-Nil, Faint, Foul or Forbidding) can guide follow-up dosage: 200 mg once daily to continue for nil or faint smell; breakthrough courses of 400 mg thrice daily ×1 week for foul smell and 2 weeks for forbidding smell, followed by 200 mg once daily.

The effectiveness and limitations of maintenance metronidazole and the SNIFFF ladder should be prospectively evaluated.