Duration of action of sildenafil citrate in men with erectile dysfunction.
ABSTRACT Viagra (sildenafil citrate) has a rapid onset of action for the treatment of erectile dysfunction (ED). However, its duration of action has not been thoroughly investigated. Practical knowledge of the time window available for sexual intercourse would be valuable for couples planning sexual activity.
We investigated the duration of action of sildenafil in men with ED.
This was a double-blind, randomized, placebo-controlled, four-way crossover study of 16 men, mean age of 55 years (range, 36-68 years) with ED of no known organic cause. Participants received oral sildenafil (100 mg) or placebo 1, 8, or 12 hours before visual sexual stimulation (VSS). Measurements included the duration of erections of >or= 60% rigidity, assessed by penile plethysmography (RigiScan), and the proportion of sildenafil responders, defined as patients with erections of >or= 60% rigidity for >or= 4 minutes and >or= 50% improvement over erections achieved in their placebo arm. Self-assessed duration of grade 3 (hard enough for penetration) or grade 4 (fully hard) erections was also recorded.
At 1, 8, and 12 hours after dosing with sildenafil, the mean duration of erections with >or= 60% rigidity was 26, 11, and 8 minutes, respectively, compared with only 3 minutes after placebo dosing (P < 0.05). However, the mean duration of self-assessed erections was 33, 23, and 16 minutes, respectively, compared with 7 minutes after placebo dosing (P < 0.05), and was greater than that assessed by RigiScan. Of the 69% sildenafil responders at 1 hour, 82% responded at 8 hours and 45% responded at 12 hours after sildenafil administration.
Sildenafil improved objective and self-assessed erectile function in men with ED, and the duration of action of sildenafil was longer than that previously reported. These data suggest that sildenafil may be effective in a significant proportion of men with ED up to 12 hours after being taken.
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ABSTRACT: The study was to compare treatment preference, efficacy, and tolerability of sildenafil citrate (sildenafil) and tadalafil for treating erectile dysfunction (ED) in Chinese men naοve to phosphodiesterase 5 (PDE5) inhibitor therapies. This multicenter, randomized, open-label, crossover study evaluated whether Chinese men with ED preferred 20-mg tadalafil or 100-mg sildenafil. After a 4 weeks baseline assessment, 383 eligible patients were randomized to sequential 20-mg tadalafil per 100-mg sildenafil or vice versa for 8 weeks respectively and then chose which treatment they preferred to take during the 8 weeks extension. Primary efficacy was measured by Question 1 of the PDE5 Inhibitor Treatment Preference Questionnaire (PITPQ). Secondary efficacy was analyzed by PITPQ Question 2, the International Index of Erectile Function (IIEF) erectile function (EF) domain, sexual encounter profile (SEP) Questions 2 and 3, and the Drug Attributes Questionnaire. Three hundred and fifty men (91%) completed the randomized treatment phase. Two hundred and forty-two per 350 (69.1%) patients preferred 20-mg tadalafil, and 108/350 (30.9%) preferred 100-mg sildenafil (P < 0.001) as their treatment in the 8 weeks extension. Ninety-two per 242 (38%) patients strongly preferred tadalafil and 37/108 (34.3%) strongly the preferred sildenafil. The SEP2 (penetration), SEP3 (successful intercourse), and IIEF-EF domain scores were improved in both tadalafil and sildenafil treatment groups. For patients who preferred tadalafil, getting an erection long after taking the medication was the most reported reason for tadalafil preference. The only treatment-emergent adverse event reported by > 2% of men was headache. After tadalafil and sildenafil treatments, more Chinese men with ED naοve to PDE5 inhibitor preferred tadalafil. Both sildenafil and tadalafil treatments were effective and safe.Asian Journal of Andrology 10/2014; DOI:10.4103/1008-682X.143244 · 2.53 Impact Factor
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ABSTRACT: The treatment modalities of erectile dysfunction range from oral pharmacotherapy to intracavernosal injections, intraurethral pellets, vacuum erectile devices, and the surgical option of penile prosthesis insertion. Oral phosphodiesterase 5 inhibitors still remain the preferred treatment for patients since they are the least invasive, not to mention that they can be prescribed by non-urologists. Due to these factors, there has been development of newer drugs with fewer side effects. This is a review of the second generation phosphodiesterase 5 inhibitor, avanafil, looking into its pharmacology as well as its clinical utility. Avanafil's faster onset and shorter duration of action has made it preferred as compared to other PDE5 inhibitors for patients with multiple comorbidities.Therapeutics and Clinical Risk Management 08/2014; 10:701-11. DOI:10.2147/TCRM.S57610 · 1.34 Impact Factor
Article: Vardenafil dihydrochloride.[Show abstract] [Hide abstract]
ABSTRACT: Vardenafil (VAR) is synthetic, highly selective, and potent inhibitor of phosphodiesterase-5 which competitively inhibits cyclic guanosine monophosphate (cGMP) hydrolysis and thus increases cGMP levels. It is clinically approved for treatment of erectile dysfunction in men, including diabetic and postprostatectomy patients. Several methods of VAR synthesis are included in this review. UV spectroscopy of VAR showed a λmax of approximately 270nm, and IR spectroscopy principal peaks were observed at 3420 (NH), 1724 (CO), 1600 (CC, and CN), 1491 (CHCH) cm(-1). Characteristic carbonyl (CO) carbon was observed in nuclear magnetic resonance spectroscopy at 162.44ppm. The molecular mass was observed at m/z=488.9 (molecular weight=488.2) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of vardenafil are also described in this profile. Pharmacokinetic properties of VAR have great impact on efficacy. VAR is rapidly absorbed and slowly metabolized, with an absolute bioavailability of 15%. It is extensively metabolized by CYP3A4 into several metabolites, the most pharmacologically active of which is N-desethyl VAR (M1). The elimination half-life of VAR and M1 is about 4-5h. VAR is primarily excreted as metabolites in the feces and to a small extent in urine. VAR is generally well tolerated, with a favorable safety profile and few transient side effects, including headache, flushing, dyspepsia, and rhinitis.Profiles of Drug Substances, Excipients and Related Methodology 01/2014; 39:515-44. DOI:10.1016/B978-0-12-800173-8.00009-X