Hair Analysis for Pharmaceutical Drugs. II. Effective Extraction and Determination of Sildenafil (Viagra) and Its N-Desmethyl Metabolite in Rat and Human Hair by GC-MS.

Off-line HPLC method combined to LC–MS for the determination of sildenafil and its active metabolite in post-mortem human blood according to confirmation criteria

“…Lewis and Johnson [10] reported the detection of both sildenafil and N-desmethylsildenafil in post-mortem fluids and tissues, while Weinmann et al [11] reported their detection in urine and tissue samples using liquid chromatography tandem mass spectrometry (LC-MS/MS) system. Al-Ghazawi et al [12] developed a method for the determination of both analytes in plasma using electrochemical detection, Cooper et al [13] in plasma using UV-vis detector and Saisho et al [14] in human hair by GC-MS. Although most of these methods are sensitive and accurate, none of them describe how to overcome the inadequate LC-MS fragmentation of both sildenafil and its active metabolite in human blood.…”

Does glimepiride alter the pharmacokinetics of sildenafil citrate in diabetic nephropathy animals: investigating mechanism of interaction by molecular modeling studies

“…[16], while nondiabetic rats (control group, n=8) received 2.5 mL kg −1 citrate buffer. Diabetes was confirmed by measuring blood glucose level 72 h after injection of STZ.…”

Determination of the PDE-5 Inhibitors and Their Analogues by GC-MS and TMS Derivatization

“…Among the generally used silylation reagents, BSTFA and MTBSTFA were employed for derivatization of the hydroxylated analogues as they showed better derivatizing efficiency than TMSI. Referring to the previous report 8 , the derivatization process was established as follows: 30 µL of derivatizing reagent (BSTFA or MTBSTFA) was added to a 10 mL test tube containing 30 µL of the standard solution (100 mg/L, in ethyl acetate). The test tube was capped and derivatized at 90 o C for 40 min.…”