Sildenafil (Viagra) for male erectile dysfunction: Results

Results

Twenty-seven clinical trial reports were made available, all prepared for a marketing authorisation application, and dated September 1997. Some of these were single dose use in laboratory setting with penile plethysmography as an outcome. Others were open extensions of randomised studies. These were not useful, and 17 were excluded; details of excluded studies and reasons for exclusions are given in Additional File 1. There were no details of any ongoing studies.

Ten studies could be included (study report numbers 101, 102, 103, 106, 355, 356, 359, 361, 363, 364) with 1846 men given sildenafil (25 mg to 100 mg) and 1131 given placebo. An additional 277 men were given canadian sildenafil at 5 mg or 200 mg. Details of trial design for the included studies is given in Additional File 2. Nine were parallel group and one had a crossover design, with fixed doses of sildenafil, or dose-optimised generic sildenafil, or both, and all had a placebo comparator group. Study duration was a minimum of six weeks and a maximum of six months.

Description of included studies
The number or percentage of men with various efficacy (more than 60% or 40% success, global rating, number erections and successful attempts at intercourse)(including treatment related adverse events and discontinuations) and adverse event outcomes are shown for individual trials in Additional File 3. These outcomes were taken at 12 weeks, or at a time as close to 12 weeks as possible.

All ten of the included clinical trial reports had a quality score of 3 (two) or 4 (eight) out of 5. All were randomised but only two stated how randomisation was achieved. All stated that they were double blind, and six explained how blinding was achieved (double-dummy, identical placebo). All studies described withdrawals clearly and were performed on an intention-to-treat basis incorporating patients with unsuccessful attempts for reasons not associated with sildenafil drug.

For inclusion in a study a man typically had to have a minimum six-month history of erectile dysfunction, be 18 years or older, be in a heterosexual relationship for at least six months and be able to give written consent. There was typically a long (21 point) list of exclusions that included anatomical deformities, other sexual disorders, diabetes with poor control and/or untreated proliferative retinopathy, recent (six month) history of heart attack or stroke, significant cardiovascular disease, active peptic ulceration or bleeding, use of other treatments for erectile dysfunction and known history of retinitis pigmentosa. All of the clinical exclusions were sensible and would form part of clinical advice regarding advisability of any new treatment. Nine of the ten studies described men as having erectile dysfunction of organic, mixed and psychogenic aetiology; a small number of men in the trials also had diabetes.

Typically men would attend for a screening visit to record medical information and to have a physical examination. Treatments were to be taken as required before anticipated sexual activity on an outpatient basis over periods up to 12 weeks. No more than one treatment was to be taken on any one day.

Efficacy was determined using the 15 questions of the IIEF questionnaire, plus a global efficacy assessment (“Has the treatment you have been taking over the past four weeks improved your erections?”), plus a log or erectile function recording details of erections, their hardness, its duration, and whether or not erection was maintained long enough to complete the sexual activity. The main reported outcomes were responses to IIEF questions 3 (“Over the past four weeks, when you attempted sexual intercourse, how often were you able to penetrate your partner?”) and question 4 (“Over the past four weeks, during sexual intercourse, how often were you able to maintain your erection after you had penetrated your partner?”).

Adverse events, observed or volunteered, were recorded, and investigators were to pursue all adverse events. Serious adverse events were defined as fatal, life-threatening, permanently disabling, requiring hospital admission, congenital abnormality, cancer or overdose, or considered serious enough for immediate reporting.

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