Abstract
Aim
There is a lack of data supporting the use of doxycycline as a single agent after removing infected orthopaedic metalwork. We evaluated the efficacy and safety of doxycycline compared with other single antibiotic regimens used at our specialist orthopaedic hospital.
Methods
A retrospective observational study including all adult patients diagnosed with an orthopaedic metalwork infection due to staphylococci. All patients were managed with the removal of metalwork, and multiple intraoperative samples were sent for culture, followed by the administration of at least four weeks of oral antibiotics. Antibiotic selection was on the recommendation of an infection consultant.
Infection outcome was assessed as the proportion of patients meeting the OVIVA Trial definition of definite failure at follow-up. The probability of definite failure for doxycycline and the alternatives group was estimated using the Kaplan-Meier survival method. All adverse drug reactions (ADR) during treatment were analysed.
Results
Seventy-nine orthopaedic metalwork infections were identified between July 2017 and July 2021. Forty-four were prosthetic joints, and 35 were fracture-related metalwork. In 54 cases, the infecting organism was Staphylococcus aureus, and 25 were due to coagulase-negative staphylococci.
Forty-four were treated with doxycycline 100mg 12 hourly, and 35 were treated with alternatives (flucloxacillin 1g 6-hourly n=21 and clindamycin 450mg 6-hourly n=14). Overall, 70 patients (88.6%) were infection-free after a median follow-up of 23 months (IQR, 19 – 44). 38 (82.3%) were infection-free in the doxycycline group compared with 32 (91.4%) patients treated with alternatives. Of the failures in the alternatives group, all 3 received flucloxacillin. Survival analysis showed no significant difference in time to treatment failure between doxycycline and alternative antibiotics.
Eighteen patients experienced an ADR: 2 nausea, one rash and one vaginal candidiasis due to doxycycline. Four diarrhoea, one reflux, two rashes and one headache due to clindamycin; 1 nausea and five diarrhoea due to flucloxacillin. Four patients required discontinuation therapy, two due to clindamycin and two due to flucloxacillin.
Conclusions
In our cohort of patients, doxycycline monotherapy was an effective and well-tolerated oral option for treating staphylococcal infection following debridement and removal of orthopaedic metalwork.
