Analysis Of Sildenafil Research Articles

Optimization and Validation of HPLC-UV Method for the Determination of Vardenafil, Sildenafil, and Tadalafil in Honey-Mixed Herbal Sachets Using a Design of Experiment

A method was developed for the simultaneous determination and analysis of sildenafil, vardenafil, and tadalafil in honey-mixed herbal sachets using high-performance liquid chromatography with a UV detector (HPLC–UV). This method eliminates the employment of complex procedures and abolishes time-consuming and labour-intensive pre-treatment processes. In ten minutes, the separation process (at 25oC) of sildenafil, vardenafil, and tadalafil using a C18 150 mm × 4.6 mm x 5 μm column (Shim-pack GIST) was successful with high selectivity and sensitivity. The mobile phase was a 60:40 (v/v) mixture of 0.1 percent formic acid in water and 0.1 percent formic acid in acetonitrile. Using the mobile phase as an extraction mixture, it gave recoveries in the range of 93.0-103.3% at spike levels of 50–150 mg/kg with relative standard deviations (RSDs) lower than 10%. The intra-day and inter-day precision results were in the range of 0.4–0.8% and 1.0–1.7%. Furthermore, the retention times for sildenafil acid, vardenafil acid, and tadalafil were 1.93, 2.47, and 9.62 minutes, respectively, and the limits of detection (LOD) were 1.70, 2.16, and 1.03 mg/L, while the limits of quantification (LOQ) were 5.65, 7.21, and 3.42 mg/L.

Investigation of the Presence of Sildenafil in Herbal Dietary Supplements by Validated HPLC Method.

As the first FDA-approved phosphodiesterase type 5 inhibitor, sildenafil (SDF) is widely used in the treatment of erectile dysfunction due to its strong pharmacodynamic activity. Since many food supplements are now involved in illegal adulteration, the presence of SDF in food supplements is very important because of their toxicological risks. In this study a simple fast, reliable high-performance liquid chromatography method with ultraviolet (UV) detector has been developed and validated for SDF analysis in herbal dietary supplements (HDSs). 10 mM phosphate buffer containing 0.1% triethylamine (pH 3.5) and acetonitrile (65:35, v/v), as mobile phase was applied isocratically to a reverse phase C18 analytical (4.6×250 mm, 5 μm) column. Chromatographic separation was achieved by a C18 reverse-phase analytical column 4.6×250 mm, 5 μm particle size, using acetonitrile, with 10 mM phosphate buffer containing 0.1% triethylamine (65:35, v/v, pH 3.5) as a mobile phase. The mobile phase flow rate was 1 mL min-1 and the column temperature was 35°C. The UV detector was set at 293 nm. The liquid-liquid extraction method used in the study provided a simple and practical method for the recovery of SDF in HDSs and their obtained values ranged from 87.6 to 111.7%. The method showed linearity with an excellent correlation coefficient (r2>0.999). Moreover, it was specific and sensitive with the limit of quantification, 6.5 ng mL-1. Intraday and interday method precision was ≤8.2 (relative standard deviation %). Intraday and interday method accuracy was between -4.0 and 7.1 (RE%). The method was strong according to the robustness test results obtained from UV detection, mobile phase buffer pH, column temperature, and flow rate changes. The described procedure was simple, fast, precise, and feasible for routine adulteration analysis of SDF, especially in food control or toxicology laboratories. This method was successfully applied to 50 individual solid and liquid form HDSs. The results showed that 37 out of 50 samples of HDSs (represented 74.0%) examined contained SDF between 0.01 and 465.47 mg/g, 150.87±127.48 (mean ± standard deviation), which could lead to serious health problems and might even be fatal for consumers. The described procedure was found to be simple, rapid, precise and feasible for routine adulteration analysis of SDF, especially in food control or toxicology laboratories.

Analysis of Sildenafil in Liquor and Health Wine Using Surface Enhanced Raman Spectroscopy.

The illegal adulteration of sildenafil in herbal food supplements and alcoholic drinks immensely threatens human health due to its harmful side-effects. Therefore, it is important to accurately detect and identify the presence of sildenafil in alcoholic drinks. In this study, Opto Trace Raman 202 (OTR 202) was used as surface enhanced Raman spectroscopy (SERS) active colloids to detect sildenafil. The results demonstrated that the Raman enhancement factor (EF) of OTR 202 colloids reached 1.84 × 107 and the limits of detection (LODs) of sildenafil in health wine and liquor were found to be as low as 0.1 mg/L. Moreover, the SERS peaks of 645, 814, 1235, 1401, 1530 and 1584 cm−1 could be qualitatively determined as sildenafil characteristic peaks and the relationship between Raman peak intensity and sildenafil concentration in health wine and liquor were different. There was a good linear correlation between Raman peak intensity, and sildenafil concentration in health wine ranged 0.1–1 mg/L (0.9687< R2 < 0.9891) and 1–10 mg/L (0.9701 < R2 < 0.9840), and in liquor ranged 0.1–1 mg/L (0.9662 < R2 < 0.9944) and 1–20 mg/L (0.9625 < R2 < 0.9922). The relative standard deviations (RSD) were less than 5.90% (sildenafil in health wine) and 9.16% (sildenafil in liquor). The recovery ranged 88.92–104.42% (sildenafil in health wine) and 90.09–104.55% (sildenafil in liquor). In general, the sildenafil in health wine and liquor could be rapidly and quantitatively determined using SERS technique, which offered a simple and accurate alternative for the determination of sildenafil in alcoholic drinks.

Rapid Resolution RP-HPLC-DAD Method for Simultaneous Determination of Sildenafil, Vardenafil, and Tadalafil in Pharmaceutical Preparations and Counterfeit Drugs

A novel and Rapid Resolution Reversed-Phase High-Performance Liquid Chromatography-Diode Array Detector method has been developed and validated for the simultaneous determination of sildenafil, vardenafil, and tadalafil in pharmaceutical preparations and counterfeit drugs. An Agilent Zorbax SB C8 column (50 × 4.6 mm i.d., 1.8 μm particle size) was used. The mobile phase consisted of a mixture of 0.030 M of ammonium formate (adjusted to pH 3.0 with formic acid) and acetonitrile in the ratio 70:30. Ultraviolet (UV) detection was performed at 230 nm. Total run time was 7 min; these three drugs were eluted at the retention times of 1.654, 2.032, and 5.067 min for vardenafil, sildenafil, and tadalafil, respectively. The method was validated for accuracy, precision, linearity, specificity, and sensitivity. From the validation study, it was found that the method is specific, rapid, accurate, precise, and reproducible. Calibration curves were linear over the concentration ranges of 0.2–200 μg ml−1 for sildenafil, vardenafil, and tadalafil. The limits of detection (LOD) values were 1.0, 1.1, and 1.0 ng and the limit of quantification (LOQ) values were 2.0, 2.1, and 2.0 ng for sildenafil, vardenafil, and tadalafil, respectively. The method is rapid both for routine quantitative analysis of sildenafil, vardenafil, and tadalafil in pharmaceutical preparations and screening their suspected counterfeit drugs.

Development of a liquid chromatographic method for bioanalytical applications with sildenafil

An improved HPLC method was developed for the determination of sildenafil concentrations in plasma. Analysis of sildenafil in plasma samples was simplified by utilizing a one-step liquid–liquid extraction after alkaline treatment of only 1 ml of plasma. The lower limit of quantitation was 10 ng/ml with a coefficient of variation of less than 20%. A linear range was found to exist from 10 to 1000 ng/ml. This HPLC method was validated with precisions (coefficient of variation, C.V.) for inter- and intra-day runs of 0.41–11.15% and 0.36–8.05%, respectively, and accuracies (the relative error of the mean, REM) for inter- and intra-day runs of −8.72–6.81% and 0.41–11.15%, respectively. A bioavailability study of sildenafil was performed on one normal healthy male volunteer by analyzing sildenafil plasma concentrations with this validated HPLC method. Results demonstrated that this HPLC method is appropriate for applications to bioavailability studies of sildenafil. In addition, an example of the influence of the co-administration of grapefruit juice on sildenafil pharmacokinetics in a healthy volunteer is presented.

Tough Choices: The Cost-Effectiveness of Sildenafil

Smith and colleagues' cost-effectiveness analysis of sildenafil (Viagra) raises a fundamental and challenging issue associated with this therapeutic advance: Should health insurance pay for the tre...