Sildenafil
Also known as: Viagra, Revatio, Sildenafil citrate, Sildenafil
Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
Sildenafil is an FDA-approved PDE5 inhibitor for erectile dysfunction (Viagra) and pulmonary arterial hypertension (Revatio). It is not anabolic and does not raise testosterone. On cycle it is used as a support medication for erectile function, blood flow / 'pumps', and endothelial/BP support. It is not on the WADA Prohibited List. Rated 1 (basically natty) because it does nothing to move the muscular/physique/performance ceiling beyond natural. It is a vasodilating libido/erectile-function drug, not a muscle-building, fat-burning, or hormone-raising one.
Overview
A short-acting phosphodiesterase type-5 (PDE5) inhibitor, the drug in Viagra (erectile dysfunction) and Revatio (pulmonary arterial hypertension). It relaxes vascular smooth muscle and enhances blood flow, most famously to the penis. Its ~4-hour half-life makes it a fast-on, as-needed drug rather than a low-dose daily one like tadalafil. On cycle it is used for erectile function, 'pumps' and vascular/blood-pressure support.
Important Warnings
- •NEVER combine with nitrates (nitroglycerin, isosorbide, 'poppers'/amyl nitrite). The combination can cause catastrophic, life-threatening hypotension. Nitrates should not be given within 24 hours of a sildenafil dose.
- •Do not combine with soluble guanylate cyclase stimulators such as riociguat.
- •Caution with alpha-blockers and other blood-pressure medications, additive hypotension (separate dosing where advised).
- •Do not stack with another PDE5 inhibitor (e.g. tadalafil): additive hypotension and side effects.
- •An erection lasting more than 4 hours (priapism) is a medical emergency. Seek care immediately.
- •Stop and seek urgent care for sudden vision or hearing loss.
- •It does not raise testosterone or treat the hormonal causes of low libido. It is a blood-flow drug.
Purpose & Use Cases
Erectile Dysfunction (FDA-approved)
The original Viagra indication: improves blood-flow-dependent erectile function. Taken as-needed, typically about an hour before activity.
Erectile Function On Cycle
Counters cycle-related ED: from suppressive compounds ('deca dick' from nandrolone/trenbolone) or from crashed estrogen. A go-to support med, taken as-needed rather than daily.
Pulmonary Arterial Hypertension (FDA-approved)
As Revatio, it lowers pulmonary arterial pressure and improves exercise tolerance in PAH, dosed on a fixed thrice-daily schedule (distinct from the as-needed ED use).
Pumps / Blood Flow
Enhanced vasodilation gives fuller 'pumps'; some athletes use it hoping better muscle blood flow aids training, though efficacy is unclear and the effect is non-anabolic.
Benefits
- Reliable, fast-acting erectile-function support, including cycle-induced ED
- Fast onset (roughly 20-30 minutes)
- Improves blood flow / 'pumps'
- FDA-approved and, since patent expiry, cheap as a generic
- Non-hormonal; does not affect the HPTA
Good to Know
The as-needed PDE5 inhibitor
Sildenafil (Viagra) has a ~4-hour half-life and fast ~20-30 minute onset, so it is taken as-needed before sex rather than low-dose daily. If you want a continuous on-cycle "always-on" PDE5 effect for erectile/BP/pump support, tadalafil's ~17.5h half-life fits that better; sildenafil is the punchier, shorter-acting option.
Never combine with nitrates
PDE5 inhibitors plus nitrates (nitroglycerin, isosorbide, 'poppers'/amyl nitrite) or guanylate cyclase stimulators (riociguat) can cause catastrophic, life-threatening hypotension. This is the one hard rule with any PDE5 inhibitor.
Not prohibited by WADA
Sildenafil is not on the WADA Prohibited List, so it is a freely usable support compound for tested athletes, unlike most of what it is stacked with. It has even been studied for exercise performance at high altitude, though efficacy there is unclear.
Dosage Guidelines
| Experience Level | Dosage Range |
|---|---|
| Beginner | 25 – 50 mg/day |
| Intermediate | 50 – 100 mg/day |
| Advanced | 100 – 100 mg/day |
ED tablets come in 25, 50 and 100mg; 50mg is the usual starting dose, taken about an hour before sex, no more than once per day. Lower 25mg starting doses are advised for older users, hepatic/severe renal impairment, or those on CYP3A4 inhibitors (e.g. one 25mg dose per 48h with HIV protease inhibitors). The PAH use is different: a fixed 20mg three-times-daily schedule under the brand Revatio. Because its half-life is only ~4h, sildenafil suits as-needed use rather than the low-dose-daily approach common with tadalafil.
Terminal half-life of sildenafil and its active metabolite, much shorter than tadalafil (~17.5h), which is why sildenafil is dosed as-needed rather than daily.
Side Effects
Headache
commonThe most common side effect, from vasodilation.
Lower the dose; hydration helps.
Flushing / Nasal Congestion
commonFacial flushing and a stuffy nose from vasodilation.
Generally mild and transient.
Dyspepsia / Indigestion
commonHeartburn or stomach upset.
Take with food; lower the dose.
Visual Disturbance (Cyanopsia)
uncommonA transient blue tint to vision, hazy vision, or altered light perception, attributed to cross-inhibition of retinal PDE6. More associated with sildenafil than tadalafil.
Transient and dose-related; usually resolves as the drug clears.
Priapism
rareA painful erection lasting more than 4 hours: a medical emergency that can permanently damage tissue if untreated.
Seek emergency care immediately for an erection lasting >4 hours.
Sudden Vision / Hearing Loss (NAION)
rareRare reports of sudden decreased vision (non-arteritic anterior ischemic optic neuropathy, NAION) or sudden hearing loss.
Stop and seek urgent care if sudden vision or hearing changes occur.
General Mitigation Strategies
Most side effects (headache, flushing, indigestion, nasal congestion, blue-tinted vision) are mild, dose-dependent and transient, start at 25-50mg. The non-negotiable safety issue is the nitrate interaction (see warnings). Priapism and sudden vision/hearing loss are rare but emergencies. Because it lowers blood pressure, be careful stacking it with other antihypertensives, alpha-blockers, or alcohol.
Post Cycle Therapy (PCT)
Not hormonal. No PCT required. It supports erectile function via blood flow but does not restore testosterone or fix the hormonal causes of low libido.
How It Works
Sexual stimulation releases nitric oxide, which activates guanylate cyclase and raises cyclic GMP (cGMP), relaxing smooth muscle. PDE5 is the enzyme that breaks cGMP down; sildenafil inhibits PDE5, so cGMP persists and smooth-muscle relaxation / vasodilation is enhanced and prolonged. In the penis this improves blood flow and erections; in the pulmonary vasculature it lowers pulmonary arterial pressure (the basis for the PAH indication). It has no hormonal or anabolic action whatsoever. Some cross-affinity for retinal PDE6 explains the transient blue-tinted vision (cyanopsia) users occasionally report.
Fundamentals
Reference on the practices relevant to Sildenafil: how they are done and where they go wrong. Not a recommendation to use it.
Legal Status
FDA-approved for erectile dysfunction (Viagra, 1998) and pulmonary arterial hypertension (Revatio). US patent expired 2020; generics widely available. OTC as Viagra Connect in the UK since 2018.
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
Sildenafil (like PDE5 inhibitors generally) is not on the WADA Prohibited List and is permitted in and out of competition. Some athletes have used it off-label believing it enhances muscle blood flow / performance, but this is not a doping-control concern for this drug.