LC-MS/MS determination of avanafil and its metabolites in rat plasma and brain: pharmacokinetic study after oral administration and transdermal film application

Avanafil (AVA) has been FDA approved in 2012 as a phosphodiesterase-type five inhibitor drug (PDE-5), for the treatment of erectile dysfunction (ED). It was necessary to study the pharmacokinetics and bioavailability parameters of AVA since it exhibits side effects, a long time from drug administration. As a result of this, we described a sensitive high-performance-liquid chromatography-triple quad-mass spectrometric method (LC-QqQ-MS) for the analysis of AVA in rat plasma and brain. Furthermore, the concentrations of AVA and its primary metabolites were determined in rat brain since it is known that PDE-5 inhibitor drugs are capable of crossing the blood–brain barrier (BBB). The liquid–liquid extraction method was developed, optimized, and applied for maximum recovery of AVA from plasma and brain homogenates. The percentage of recovery was 96.60 ± 2.44% and 94.50 ± 1.86%, in rat plasma and brain homogenate, respectively. The separation was performed on a Nucleodur C18 column, with mobile phase composed of 0.1% formic acid and acetonitrile (29 : 71, v/v), at flow rate 0.5 mL min−1, and monitored with QqQ-MS applying positive multiple reaction monitoring (MRM) mode. The calculated pharmacokinetic parameters, noncompartmental model, were: Cmax 1503.82 ± 354.11 ng mL−1 with a t1/2 value of 4.87 ± 0.42 h and Cmax 141.94 ± 22.57 ng mL−1 with a t1/2 value of 7.05 ± 1.59 h, for oral AVA suspension and transdermal film, respectively. The average percentage of total metabolites in plasma and brain was 27.1 ± 2.2% and 7.0 ± 1.0%, respectively.