Abstract

In this study we are presenting short-term and long-term protocols to investigate the stability of triamcinolone, triamcinolone acetonide, prednisone, betamethasone, deflazacort and formoterol in male and female urines at different temperatures (25, 37, 55°C for short-term; -20 and 4°C for long-term) and pH values (5.0, 7.0, 9.0). To assess the degradation rate and nature, the concentration of the target analytes, pH, specific gravity and nitrites levels were measured every day for 7 days in short-term stability protocol, and every three days for three months in long-term stability protocol. Results were compared with those obtained in aliquots stored at -80°C, since at this temperature thermal/microbial degradation is totally inhibited. Concerning short-term stability, data showed that, in normal conditions, although all studied substances underwent extensive degradation after 7 days at 37°C and moderate degradation at 25 and 55°C, their levels did not decrease remarkably for at least 4 days; besides, degradation kinetics appeared to be pH-dependent, being slower at pH 5.0 and 9.0 than at pH 7.0; additionally, since degradation at 37°C was more pronounced than 55°C, it can be assessed that both microbiological and thermal factors affect substances stability and the increase of pH values and nitrites concentration at 37 and 25°C confirms this evidence. Long-term stability results showed that investigated substances were stable at -20°C for 91 days and at 4°C for at least 30 days. Finally, no marked differences were observed in degradation rate between female and male urine. Verf.-Referat