During the anaerobic tests, such parameters as total biogas production and methane concentration in biogas were monitored. At the end of the anaerobic tests, antibiotic concentrations left in the slurries were detected. The results showed that Ceftiofur was the most degradable drug (approximately 70% of the initial content was degraded), while Danofloxacin and Lincomycin were less degradable (30-34% of the total initial content). The greatest inhibition of anaerobic digestion was observed with the drug association of Lincomycin and Spectinomycin (Micospectone), which presented the least physical degradability (heat treatment) and biological degradability.