Susceptibility and resistance of Sporothrix brasiliensis to branded and compounded itraconazole formulations

Itraconazole is the first drug of choice for the treatment of sporotrichosis and it is available at different concentrations for veterinary patients. However, therapeutic failure has been reported, limiting clinical treatment. This study evaluated the in vitro efficacy of brand-name and compounded itraconazole formulations against Sporothrix brasiliensis and estimated the itraconazole content in each tested formulation. Oral capsules were acquired from two brand-name products for human (H-IND) and veterinary (V-IND) uses, and three from compounding pharmacies in Pelotas, RS, for human (H-COMP1/H-COMP2) and veterinary (V-COMP) uses. Capsule purity was analyzed by liquid chromatography–electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS). Antifungal activity was determined against 29 Sporothrix brasiliensis by the M38-A2 guideline of CLSI. H-IND/H-COMP1/H-COMP2 had high efficacy against S. brasiliensis (approximately 70% of total isolated susceptible), V-COMP showed moderate efficacy (51.7%), and V-IND was the least effective formulation (37.9%). Thirty-four percent of the total isolates were resistant to all formulations. Furthermore, itraconazole content did not match the concentration indicated by the manufacturers, ranging from 387.70 to 7.81 μg/mg (H-COMP2 > V-COMP > H-IND > H-COMP1 > V-IND). Therefore, it is possible that the formulations showed different in vitro efficacy due to the difference in their itraconazole contents. Given the emergence of antifungal resistance for all formulations, the choice product to be used must follow susceptibility testing. Stringent quality control measures are recommended for product manufactures to assure drug content uniformity.