This review demonstrated that considerable amounts of useful information are available in clinical trial reports submitted for marketing authorisation (licensing). That information adequately describes research methods used, though could be improved, perhaps using the updated CONSORT criteria. If these guidelines are becoming necessary for publication of randomised trials in our major medical journals, then they should be minimum criteria for clinical trials reports required by licensing authorities. We did not check the reports against each CONSORT criterion because the reports were from 1997 soon after the publication of the original CONSORT statement.
The efficacy results closest to the prior definition of efficacy of a man with the consistent three part outcome, consisting of an erection, sufficiently rigid for penetration, and followed by successful intercourse were the number of men in whom at least 60% or at least 40% of attempts at sexual intercourse were successful. The results for at least 60% of attempts successful are shown in Table 1 and Figure1. All doses were significantly better than placebo. In three studies 48% of men had this outcome with dose optimisation compared with 11% with placebo; the number needed to treat was 2.7 (95% CI 2.3 to 3.2). Dose-optimisation produced a significantly lower (better) NNT than a 25 mg fixed dose. …click here to read more
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.
No search strategy was required because this review was of material made available by Pfizer UK Ltd in the form of clinical trial reports used in a marketing authorisation application for sildenafil (Viagra) in September 1997. QUORUM guidelines were otherwise followed. The prior intention was to use studies that were relevant to the use of sildenafil in clinical practice. This required the setting to be the home, not the clinic, use of sildenafil as required, rather than fixed dosing schedules (such as daily tablets), and studies of a minimum duration, which we set arbitrarily as four weeks.
Excluded were studies with laboratory measures of penile tumescence or rigidity with single doses of sildenafil, studies that only investigated erectile function in a clinic setting, studies that used fixed daily dosing rather than as required, and studies that were shorter than four weeks. Included were randomised trials that investigated canadian sildenafil, with efficacy or safety data, were longer than four weeks, conducted in the home setting, and with doses in the licensed range of 25 mg to 100 mg as required, although lower and higher doses would be analysed if there were sufficient information. Clinical trials in men with erectile dysfunction caused specifically by single causes like spinal cord trauma or diabetes were not included because, taken with the other data, they would constitute clinical heterogeneity.
Meta-analyses that include otherwise unpublished randomised trials are uncommon, but are welcome, and can inform in circumstances where information is contradictory. The example of generic tramadol in acute pain, where information on 3,500 patients was made available, explained the results of two studies, one showing that tramadol was a highly efficacious analgesic, the other showing it to be no different from placebo. The truth was somewhere between. Despite the fact that canadian tramadol had been in common use in some European countries for many years, fulfilling regulatory requirements for the United States required studies to be conducted to contemporary requirements, and meta-analysis brought useful results to light.
Meta-analysis of randomised studies before a new technology has become commercially available is even more rare, though there is at least two examples. Meta-analyses are usually performed some years after first commercial availability because the publication of randomised trials performed for efficacy and/or safety reasons takes time. The importance of meta-analysis in drug development and regulatory procedures is increasingly recognised.
Viagra (sildenafil citrate) is good not only for treating male erectile dysfunction. Israeli and Australian researchers have discovered that small concentrations of the drug dissolved in a vase of water can also double the shelf life of cut flowers, making them stand up straight for as long as a week beyond their natural life span.
Viagra (Sildenafil) has been approved in over 50 countries. As of November 1998, 6.4 million prescriptions had been filled within the United States, representing over 50 million tablets dispensed. This equates to over 3.5 million men and corresponds to a cumulative exposure of 25 million man-weeks since the drug was launched in April 1998. To help track potentially important adverse events following the release of new drugs, the Spontaneous Reporting System has been developed. Spontaneous reports are based on a worldwide reporting system. Initially, reports are made to a manufacturer, a regulatory body, or both. They are received from multiple sources, including healthcare providers, consumers, media registries, the literature, and lawyers. Reports are received that may be duplicates, may be poorly detailed, or may even be spurious. Despite these limitations, the system is important to both manufacturers and regulators worldwide and is a necessary part of monitoring drug safety. Spontaneous reporting is the primary method of signal detection for events that occur at a very low incidence rate.
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