Article

RP-HPLC method development and validation for determination of dissolution and assay of sildenafil citrate tablets

Journal of Pharmacy Research 01/2010;
Source: DOAJ

ABSTRACT The aim of this study is to development and validation of a stability indicating RP-HPLC method for the determination of dissolution and assay of Sildenafil citrate tablets 50mg and 100mg using RP-HPLC with UV detector. Sildenafil citrate and related substances were baseline separated and quantitated on a C18 reverse phase column (4.6mm × 250mm, 5.0µm), using a mobile phase composed of a phosphate buffer-acetonitrile (40:60v/v,) delivered at a flow rate of 1.0mL/min, and with UV detection (lexcitation = 225nm). The method was proven to be linear over a Sildenafil citrate concentration range of 13 to 83µg/mL with a mean correlation coefficient of 0.9999.

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    ABSTRACT: Sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), is a well-tolerated and highly effective treatment for erectile dysfunction. The mechanism of action of sildenafil depends on activation of the nitric oxide (NO)-cGMP pathway during sexual stimulation, which results in corpus cavernosal smooth muscle relaxation and penile erection. Endogenously derived NO is also involved in blood pressure regulation through its effect on basal vascular tone, which is mediated by cGMP levels. Organic nitrates and NO donors exert their therapeutic effects on blood pressure and vascular smooth muscle by the same mechanism as endogenous NO. Since both sildenafil and organic nitrates exert their pharmacologic effects via increases in cGMP concentrations, a double-blind, placebo-controlled, crossover study was undertaken to investigate the effects of sildenafil coadministered with glyceryl trinitrate on blood pressure and heart rate in healthy male subjects. The hemodynamic effects of sildenafil were also evaluated in a second placebo-controlled crossover study in men with hypertension who were taking the calcium antagonist amlodipine, which has a mechanism of action that does not involve the cGMP pathway. In the first crossover study, subjects were treated with oral sildenafil (25 mg, 3 times a day for 4 days) or placebo and then challenged on day 4 with a 40-minute, stepwise, intravenous infusion of glyceryl trinitrate (0.5 mg/mL in 5% dextrose at an initial infusion rate of 2.5 microg/min and doubling every 5 minutes to a maximum rate of 40 microg/min) 1 hour after taking sildenafil or placebo. On day 5, subjects received a sublingual glyceryl trinitrate tablet (500 microg) 1 hour after taking 25 mg of sildenafil or placebo. During sildenafil treatment, the subjects were significantly less tolerant of intravenously administered glyceryl trinitrate than during placebo treatment, based on the occurrence of a >25 mm Hg decrease in blood pressure or the incidence of symptomatic hypotension (p <0.01). When a sublingual glyceryl trinitrate tablet was administered on day 5, a 4-fold greater decrease in systolic blood pressure was observed for the subjects during the sildenafil treatment period than during the placebo treatment period. The changes in heart rate were negligible during both glyceryl trinitrate challenges. In conclusion, sildenafil potentiated the hypotensive effects of glyceryl trinitrate, an organic nitrate. Thus, sildenafil administration to patients who are using organic nitrates, either regularly and/or intermittently, in any form is contraindicated. In the second crossover study, men with hypertension, who were taking 5 or 10 mg/day of amlodipine, received a single oral dose of 100 mg sildenafil or placebo. Coadministration of sildenafil did not significantly affect the pharmacokinetics of amlodipine. In the 4 hours after dosing, differences in the mean maximum change from baseline in supine systolic and diastolic blood pressures between the sildenafil plus amlodipine and the placebo plus amlodipine treatment periods were -8 mm Hg and -7 mm Hg, respectively (p < or =0.002). The mean maximum supine heart rate increased 2.1 beats/min during sildenafil plus amlodipine treatment and decreased 1.5 beats/min during placebo plus amlodipine treatment (p <0.02). The adverse events in this study were predominantly mild or moderate and did not cause discontinuation of treatment. Adverse events considered to be related to sildenafil treatment included headache, nausea, and dyspepsia. In patients with hypertension who were taking amlodipine therapy, sildenafil produced additive, but not synergistic, reductions in blood pressure. The difference in the mean maximum change from baseline in blood pressure between sildenafil plus amlodipine and placebo plus amlodipine was comparable to the decrease in blood pressure reported for healthy men taking sildenafil alone. (ABSTRACT TRUNCATED)
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    ABSTRACT: Results In an intention-to-treat analysis, women treated with sildenafil had a mean Clinical Global Impression-sexual function score of 1.9 (95% confidence interval (CI), 1.6-2.3) compared with those taking placebo (1.1; 95% CI, 0.8-1.5), with a mean end point difference of 0.8 (95% CI, 0.6-1.0; P=.001). Assigning baseline values car- ried forward to the 22% of patients who prematurely discontinued resulted in a mean end point in the sexual function score of 1.5 (95% CI, 1.1-1.9) among women taking sildenafil compared with 0.9 (95% CI, 0.6-1.3) among women taking placebo with a mean end point difference of 0.6 (95% CI, 0.3-0.8; P=.03). Baseline endocrine levels were within normal limits and did not differ between groups. The mean (SD) Hamil- ton scores for depression remained consistent with remission in both groups (4.0 (3.6); P=.90). Headache, flushing, and dyspepsia were reported frequently during treat- ment, but no patients withdrew because of serious adverse effects. Conclusion In this study population, sildenafil treatment of sexual dysfunction in women taking SRIs was associated with a reduction in adverse sexual effects.
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    ABSTRACT: Erectile dysfunction is a common multi-factorial complication of diabetes mellitus. Numerous strategies have been tried to overcome this diabetic complication. In recent years, phosphodiesterase type 5 (PDE-5) inhibitors have been introduced in the management of erectile dysfunction. The objective of this review was to assess the effect of PDE-5 inhibitors on the management of erectile dysfunction in diabetic men. Studies were obtained from computerised searches of MEDLINE, EMBASE and The Cochrane Library. Randomised controlled trials, in which treatment with PDE-5 inhibitors was compared to control, in diabetic patients with erectile dysfunction. Two reviewers independently extracted data and assessed trial quality. Eight randomised controlled trials were identified. A total 976 men were allocated to receive a PDE-5 inhibitor and 741 were randomised to the control groups. Overall, 80% of the participants suffered from type 2 diabetes mellitus. The weighted mean difference (WMD) for the International Index of Erectile Function (IIEF) questions 3 and 4 (frequency of penetration during and maintaining erection to completion of intercourse) was 0.9 (95% CI 0.8 to 1.1) and 1.1 (95% CI 1.0 to 1.2) at the end of the study period, in favour of the intervention group. The WMD for the IIEF erectile dysfunction domain at the end of the study period was 6.6 (95% CI 5.2 to 7.9) in favour of the PDE-5 inhibitors arm. The relative risk (RR) for answering "yes" to a global efficacy question ( "did the treatment improve your erections?") was 3.8 (CI 95% 3.1 to 4.5) in the PDE-5 inhibitors compared with the control arm. The WMD between the percentage of successful attempts in the PDE-5 inhibitors and in the control arm was 26.7 (95% CI 23.1 to 30.3). Mortality was not reported in any of the included trials. Adverse cardiovascular effects were reported in one study. Headache was the most frequent adverse event reported, flushing was the second most common event, with upper respiratory tract complaints and flu like syndromes, dyspepsia, myalgia, abnormal vision and back pain also reported in a descending order of frequency. The overall risk ratio for developing any adverse reaction was 4.8 (CI 95% 3.74 to 6.16) in the PDE-5 inhibitors arm as compared to the control. Sufficient evidence exists that PDE-5 inhibitors form a care that improves erectile dysfunction in diabetic men.
    Cochrane database of systematic reviews (Online) 02/2007; · 5.70 Impact Factor

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