Desenvolvimento de método analítico indicativo de estabilidade para análise de tadalafila e sildenafila associados, cinética de fotodegradação e estudo toxicológico

Abstract

Nowadays, tadalafil (TAD) and sildenafil (SIL) are counterfeit medicines with the highest incidence in the illegal market. Associations of these drugs are available in different concentrations from those authorized by regulatory agencies, without any pharmacological study or compliance with Good Manufacturing Practices (GMP) during their production. Likewise, inadequate environmental conditions in transportation and storage can lead to the formation of toxic degradation products. Thus, this work aims to develop and validate a stability-indicating method for TAD and SIL simultaneous determination, to evaluate the photodegradation kinetics and the biological safety of the associated drugs, degraded and not degraded. Chromatographic separation used C18 column (250 x 4.6 mm, 5μm) and the mobile phase was performed using Solution A and Solution B (30:70, v/v). The solution A contains acetonitrile:water (80:20, v/v) and solution B methanol:0.3% triethylamine pH 7.5, adjusted with o-phosphoric acid (57:43, v/v). The elution was isocratic with flow rate of 1.0 mL min-1, injection volume of 20 μL and temperature at 25 °C. Detection was achieved at 284 nm for TAD and 292 nm for SIL. The method was validated according to international guidelines. The photodegradation kinetics were evaluated using the solvents methanol and methanol:acetonitrile (50:50, v/v), in a photostability chamber equipped with a UVA lamp, for 275 min. Toxicity studies of photodegraded and non-degraded drugs were performed by in vitro cytotoxicity, mutagenicity and genotoxicity tests. The method was considered specific, linear, precise, accurate, robust and sensitive. The drugs presented first-order photodegradation kinetics when isolated and zero-order when associated. Toxicological tests demonstrated that the photodegraded drugs decreased cell viability in compared to non- degraded drugs, suggesting cytotoxic activity. It was not observed mutagenic activity under the conditions tested. Photodegraded drugs when associated showed DNA damage index, suggesting genotoxic effects. The studies developed can collaborate with forensic analysis and bring information to raise the awareness of the population about the risks of consuming counterfeit products.