Sildenafil Pivotal Trial
Oral Sildenafil in the Treatment of Erectile Dysfunction (Goldstein et al., NEJM 1998)
Evidence grade 5 of 5, Settled. Read how the Atlas grades evidence.
2 human trials, about 2 studies, ~861 participants men across two pivotal trials. The written rationale for this grade is still being prepared.
- FDA
- Pivotal trial supporting Viagra approval (1998)
Reference only. Not medical advice.
What can go wrong
Sildenafil is absolutely contraindicated with nitrates due to risk of severe hypotension; caution with alpha-blockers and unstable cardiovascular disease. The pivotal trials reported headache, flushing, dyspepsia, and transient visual disturbances as the most common adverse effects, generally mild to moderate.
This is something to take to a clinician. The Atlas can tell you what is known about sildenafil pivotal trial in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
Goldstein and colleagues' 1998 NEJM paper reported the two pivotal randomized trials of oral sildenafil that supported Viagra's FDA approval: a dose-response study and a flexible-dose study in men with erectile dysfunction of mostly organic, psychogenic, or mixed cause. Sildenafil dramatically improved erectile function, intercourse success, and patient-reported outcomes versus placebo, with a favorable tolerability profile. It established the first effective, well-tolerated ORAL treatment for ED and inaugurated the PDE5-inhibitor era that transformed men's sexual medicine.
The trial that launched the oral-ED era and made Viagra a household name.
What people take it for
What it is taken for. Approval, where it exists, covers only some of these.
How it works
Sildenafil inhibits PDE5, the enzyme that breaks down cyclic GMP in penile smooth muscle. With cGMP preserved, nitric-oxide signaling from sexual stimulation produces sustained smooth-muscle relaxation and engorgement of the corpora cavernosa - an erection enabled by, but dependent on, arousal.
What the registration trials did not settle
These were efficacy/registration trials in selected populations and used questionnaire and diary surrogates over weeks to months. They under-represented men with severe diabetic or post-prostatectomy ED (who respond less well), did not establish long-term or rare-harm safety, and - being industry-sponsored - launched a drug whose later real-world use, including recreational and non-prescribed use, went well beyond the trial population.
What people get wrong
Often saidViagra was invented as a sex drug
ActuallySildenafil was developed as a candidate ANGINA drug; its erectile effect was discovered incidentally, and the Goldstein trials formalized that observation into an approved indication.
Often saidThe trials showed Viagra works for everyone
ActuallyResponse rates were high but not universal, and the pivotal populations under-represented diabetic and post-surgical ED, where efficacy is lower.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
How we got here
Sildenafil emerged from Pfizer's UK angina program when trial volunteers reported erections. The Goldstein-led pivotal trials, published in NEJM in May 1998, supported the same-year FDA approval of Viagra, which became one of the fastest-adopted drugs in history and reframed ED as a common, treatable, openly discussed medical condition.
- Early 1990sSildenafil's erectile effect noted incidentally in angina trials
- 1996-1997Pivotal ED trials conducted
- 1998Goldstein NEJM publication; FDA approves Viagra
- 2017-2018Generic sildenafil arrives, broadening access
What the trials could not show
Limits of the studies themselves, as distinct from limits of the treatment.
- Industry-sponsored registration trials; surrogate questionnaire/diary endpoints rather than long-term outcomes; selected populations under-representing severe organic ED; short duration; limited power for rare adverse events such as NAION; men with significant cardiovascular instability were excluded.
What we do not know
- What is the true very-long-term safety record now visible at population scale?
- How should non-responders and severe organic ED be managed beyond PDE5 inhibitors?
At a glance
- Design
- Two RCTs: 24-week dose-response + 12-week flexible-dose, double-blind, placebo-controlled
- N
- ~532 (dose-response) + ~329 (flexible-dose)
- Doses
- 25, 50, 100 mg as needed
- Primary measures
- IIEF questions 3 & 4; diary success rates; global efficacy question
- Key result
- ~69-74% of attempts successful on sildenafil vs ~22% placebo (100 mg)
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Sildenafil Pivotal Trial. A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
- Where we land. We have not taken a position on this yet.
Sources
The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.
The studies that matter
Goldstein et al. (NEJM)1998
In the dose-response trial, mean IIEF erectile-function scores and the proportion of successful intercourse attempts rose dose-dependently; at 100 mg roughly 69-74% of attempts succeeded vs ~22% on placebo, with ~69-88% of men reporting improved erections by global assessment