Validated UPLC-MS/MS assay for the determination of synthetic phosphodiesterase type-5 inhibitors in postmortem blood samples

Abstract

The use of synthetic phosphodiesterase type 5 (PDE-5) inhibitors for the treatment of erectile dysfunction: sildenafil citrate (Viagra®), tadalafil (Cialis®) and vardenafil hydrochloride (Levitra®) has increased dramatically over the past 2 years. These substances are prescription drugs and must be used under medical supervision. However, they can easily be obtained over the internet from illegal sites, being a potential for a threat to public health.The development of an electrospray ionisation (ESI) ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) procedure for the simultaneous identification and quantification of three PDE5 inhibitors in blood samples was desired.Samples were prepared using Oasis® HLB solid-phase cartridges (3 cc, 60 mg) and chromatographic separation was achieved on an Acquity UPLC® HSS T3 (100 × 2.1 mm i.d., 1.8 μm particles) column with a gradient mobile phase of 0.1% formic acid and acetonitrile at a 0.5 mL/min flow rate.Quantification was achieved by multiple reaction monitoring (MRM) of two transitions per compound: m/z 475.1 > 58 e m/z 475.1 > 311.1 for sildenafil; m/z 389.9 > 267.9 e m/z 389.9 > 134.8 for tadalafil and m/z 489 > 71.9 e m/z 489 > 150.9 for vardenafil. Zolpidem-d6 (m/z 314.5 > 235.3) was used as the internal standard.Calibration curves were linear over the concentration range of 5–1000 ng/mL, with a coefficient of determination better than 0.997. The lower limits of detection and quantification for these substances were ≤3 ng/mL and ≤8 ng/mL, respectively. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.A rapid, selective and sensitive UPLC-MS/MS method using solid-phase extraction was developed for the simultaneous determination and quantification of sildenafil, vardenafil and tadalafil in blood samples.