Simultaneous determination of sildenafil and N-desmethyl sildenafil in human plasma by high-performance liquid chromatography method using electrochemical detection with application to a pharmacokinetic study.
A method which employed high-performance liquid chromatography coupled with electrochemical detection was developed for the simultaneous determination of sildenafil and its metabolite, N-desmethyl sildenafil, in human plasma has. The method was developed and validated for purposes of its application to a pharmacokinetic study in healthy volunteers after an oral dose of 50mg/tablet under fasting conditions. High precision and accuracy were demonstrated. A one-step liquid-liquid extraction further provides a simple and practical way to process plasma samples containing sildenafil with good quantitative recovery. Sampling lasted for 24h after dosing; consequently a limit of quantitation (LOQ) of 7.858 ng/mL was achieved for sildenafil whereas a LOQ of 8.675 ng/mL was obtained for N-desmethyl sildenafil. The mobile phase consisted of acetonitrile, methanol and phosphate buffer (0.05 M) (18.5:34.5:47.0, v/v/v) pH 7.68. The stationary phase was a C(8) (150 mm x 4.6 mm), 5 microm particle size operated at 27 degrees C. All analytes were stable at the pH of the supernatant, and during the analytical time window. At the applied potential of +1.20 V versus Ag/AgCl, no interferences from endogenous plasma compounds were recorded at the retention times of sildenafil, N-desmethyl sildenafil. High resolution was obtained between the analytes and the employed internal standards.
Al-Ghazawi
M
M
Department of Clinical Pharmacy, Faculty of Pharmacy, The University of Jordan, Amman, Jordan. alghazam@ju.edu.jo
Tutunji
M
M
Aburuz
S
S
D000097:Acetonitriles / Q000737:chemistry; D000284:Administration, Oral; D002021:Buffers; D002851:Chromatography, High Pressure Liquid / Q000379:methods* / Q000592:standards; D004563:Electrochemistry / Q000379:methods* / Q000592:standards; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D008297:Male; D000432:Methanol / Q000737:chemistry; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D010879:Piperazines / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D011687:Purines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D012015:Reference Standards; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000068677:Sildenafil Citrate; D012997:Solvents / Q000737:chemistry; D013450:Sulfones / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics
D000097:Acetonitriles; D002021:Buffers; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D012997:Solvents; D013450:Sulfones; D000068677:Sildenafil Citrate; D000432:Methanol; C032159:acetonitrile