Adverse effects of rifampicin in dogs and serum alanine aminotransferase monitoring recommendations based on a retrospective study of 344 dogs

Abstract

BACKGROUND: Rifampicin has been reported to have potent activity against Staphylococci, including meticillin-resistant Staphylococcus pseudintermedius. There is limited documented information regarding adverse effects and recommendations for serum biochemistry monitoring. HYPOTHESIS/OBJECTIVES: The aims of this retrospective study were as follows: (i) to document the occurrence of adverse events in dogs receiving oral rifampicin; (ii) to determine the relationship between adverse events and the dosage/duration of therapy and concurrent medications; and (iii) to report findings associated with changes on serum alanine aminotransferase (ALT). ANIMALS: Client-owned dogs. METHODS: A retrospective review of 344 medical records was carried out. Serum ALT concentrations and adverse effects were recorded and analysed. Correlations between different time intervals (days 0-9, 10-18, 19-27, 28-36 and >36) and serum ALT elevation were compared. RESULTS: Dogs received 2.9-16 mg/kg/day of rifampicin. Adverse events occurred in 16.27% of dogs (56 of 344) and included vomiting (6.97%), anorexia (6.10%) and lethargy (3.77%). Adverse events were significantly more common in dogs concurrently treated with trimethoprim-sulfamethoxazole (P = 0.018), doxycycline (P = 0.044), levothyroxine sodium (P = 0.044), cephalosporins (P = 0.002) and nonsteroidal anti-inflammatories (P < 0.001). Twenty-five of 94 dogs (26.59%) had serum elevations of ALT. These increases were significantly associated with the duration of therapy during two time periods, 19-27 days (P = 0.04) and >36 days (P = 0.01). CONCLUSIONS AND CLINICAL IMPORTANCE: Significant adverse events were noted in association with concurrent drug administration and with serum ALT elevations. Pretreatment and weekly serum biochemistry monitoring is recommended to identify dogs at risk for hepatotoxicosis.