RESUMO
Phosphodiesterase inhibitors (PDE5i) are considered the first line therapy for erectile dysfunction. All PDE5i available on the market are structurally related; their main differences relate to their pharmacokinetic parameters. For these treatments to be effective and safe, it is necessary that these drugs are in the appropriate doses and that they reach adequate concentrations in the plasma. For this purpose, it is essential to perform therapeutic monitoring using bioanalytical methods. In this way, the present work aimed to develop and validate a new bioanalytical method, based on LC-MS/MS, for the simultaneous quantification of six commercially available PDE5i (avanafil, lodenafil, sildenafil, tadalafil, udenafil, and vardenafil). For this purpose, the human plasma was extracted with diethyl ether and sulfaquinoxaline was established as an internal standard. Separation was achieved using an Xbridge C18 column at 40 °C as the stationary phase, using water and acetonitrile as the mobile phase (both with formic acid and ammonium formate) in gradient mode. The method was validated according to the current guidelines and was found to be selective, linear (from 1 to 200 ng.mL-1 for all drugs except for tadalafil which is from 5 to 200 ng.mL-1), precise, accurate, and free of residual and matrix effects. The drugs were considered stable in plasma and in solution under different conditions. The method was applied to volunteerssamples, demonstrating that the method can be used routinely and may be useful in future studies on pharmacokinetics and therapeutic monitoring.
Assuntos
Cromatografia Líquida/métodos , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/sangue , Espectrometria de Massas em Tandem/métodos , Adulto , Monitoramento de Medicamentos , Humanos , Limite de Detecção , Modelos Lineares , Masculino , Reprodutibilidade dos TestesRESUMO
OBJECTIVES: We investigated the influence of sildenafil on cardiac contractility and diastolic relaxation and examined the distribution of phosphodiesterase-5 in the hearts of hypertensive rats that were treated with by NG-nitro-L-arginine methyl ester (L-NAME). METHODS: Male Wistar rats were treated with L-NAME and/or sildenafil for eight weeks. The Langendorff method was used to examine the effects of sildenafil on cardiac contractility and diastolic relaxation. The presence and location of phosphodiesterase-5 and phosphodiesterase-3 were assessed by immunohistochemistry, and cGMP plasma levels were measured by ELISA. RESULTS: In isolated hearts, sildenafil prevented the reduction of diastolic relaxation (dP/dt) that was induced by L-NAME. In addition, phosphodiesterase-5 immunoreactivity was localized in the intercalated discs between the myocardial cells. The staining intensity was reduced by L-NAME, and sildenafil treatment abolished this reduction. Consistent with these results, the plasma levels of cGMP were decreased in the L-NAME-treated rats but not in rats that were treated with L-NAME + sildenafil. CONCLUSION: The sildenafil-induced attenuation of the deleterious hemodynamic and cardiac morphological effects of L-NAME in cardiac myocytes is mediated (at least in part) by the inhibition of phosphodiesterase-5.
Assuntos
Inibidores Enzimáticos/uso terapêutico , Coração/efeitos dos fármacos , Hipertensão/tratamento farmacológico , NG-Nitroarginina Metil Éster/uso terapêutico , Inibidores da Fosfodiesterase 5/farmacologia , Piperazinas/farmacologia , Sulfonas/farmacologia , Animais , Arteríolas/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/sangue , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/metabolismo , Diástole , Ensaio de Imunoadsorção Enzimática , Coração/fisiopatologia , Hipertensão/enzimologia , Hipertensão/fisiopatologia , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/enzimologia , Purinas/farmacologia , Ratos , Ratos Wistar , Citrato de Sildenafila , Fatores de TempoRESUMO
BACKGROUND AND PURPOSE: Oncocalyxone A (OncoA) has a concentration-dependent anti-platelet activity. The present study aimed to further understand the mechanisms related to this effect. EXPERIMENTAL APPROACH: Human platelet aggregation was measured by means of a turbidimetric method. OncoA (32-256 microM) was tested against several platelet-aggregating agents, such as adenosine diphosphate (ADP), collagen, arachidonic acid (AA), ristocetin and thrombin. KEY RESULTS: OncoA completely inhibited platelet aggregation with a calculated mean inhibitory concentration (IC50-microM) of 122 for ADP, 161 for collagen, 159 for AA, 169 for ristocetin and 85 for thrombin. The anti-aggregatory activity of OncoA was not inhibited by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). OncoA, at a concentration that caused no significant anti-aggregatory activity, potentiated sodium nitroprusside (SNP) anti-aggregatory activity (18.8+/-2.9%-SNP vs 85.0+/-8.2%-SNP+OncoA). The levels of nitric oxide (NO) or cAMP were not altered by OncoA while cGMP levels were increased more than 10-fold by OncoA in resting or ADP-activated platelets. Flow cytometry revealed that OncoA does not interact with receptors for fibrinogen, collagen or P-selectin. Nevertheless, OncoA decreased the binding of antibodies to GP Ibalpha, a glycoprotein that is related both to von Willebrand factor and to thrombin-induced platelet aggregation. CONCLUSION AND IMPLICATIONS: OncoA showed anti-aggregatory activity in platelets that was associated with increased cGMP levels, not dependent on NO and with blocking GP Ibalpha glycoprotein. This new mechanism has the prospect of leading to new anti-thrombotic drugs.