Tiamulin-nitrovin interaction in pigs: a case report and experimental reproduction

Tiamulin is a diterpenic veterinary drug widely used in swine for the control of infectious diseases, including swine dysentery and enzootic pneumonia. Tiamulin is well tolerated and only a few drug interactions have been reported with some ionophore antibiotics. A case of tiamulin adverse drug interaction with nitrovin, a nitrofuranic growth promoter, in fattening pigs from a commercial farm is described. To confirm the diagnosis, experimental reproduction was conducted using 20 healthy female pigs. The animals were randomly divided into 4 groups: 1 of them receiving feed medicated with 100 mg tiamulin hydrogen fumarate/kg, another received 20 mg nitrovin/kg to establish the harmlessness of the drugs alone. The other 2 groups received feeds containing both drugs at the previous concentrations, one of which came from the farm. In the last 2 groups clinical signs appeared 72-96 h after initially feeding pigs the tiamulin hydrogen fumarate + nitrovin-containing feed. The animals had uneasiness, anxiety, skin erythema, and rash on snout, vulva and abdomen, and increased body temperatures. No mortality occurred, and there were no characteristic findings during pathological examination. The signs disappeared after 96 h of consuming the medicated feed, leaving a slight skin thickening of the affected regions. All signs disappeared spontaneously 4-5 d after ceasing medication.