Sildenafil, sold as Viagra, was the first oral phosphodiesterase type 5 (PDE5) inhibitor. It strengthens the nitric oxide signal that relaxes smooth muscle in the penis and in the blood vessels of the lungs. The FDA approved Viagra for erectile dysfunction (ED) in March 1998. Under the brand Revatio, the same molecule is approved for pulmonary arterial hypertension (PAH), dosed three times a day.
What sets sildenafil apart from tadalafil (Cialis) is its short half-life of about 4 hours. It is taken as needed about an hour before sex, and a high-fat meal slows it down. It is also less selective against PDE6, the retinal enzyme behind its typical blue-tinged vision side effect. Outside medicine, sildenafil is the drug most often found hidden in sexual enhancement supplements flagged by the FDA, and anabolic steroid users report misusing it more often than other gym-goers.
This page summarizes what the FDA labels, clinical trials and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Phosphodiesterase type 5 (PDE5) inhibitor |
| Brands / approval | Viagra (Pfizer, now Viatris): FDA March 27, 1998 (NDA 020895); EU September 14, 1998. Revatio for PAH: FDA June 3, 2005 (NDA 021845). Generics available |
| Route | Oral tablet; Revatio also as oral suspension and intravenous injection |
| Strengths | Viagra 25, 50 and 100 mg; Revatio 20 mg tablets, 10 mg/mL suspension, 10 mg/12.5 mL injection |
| Labeled doses | ED: 50 mg as needed about 1 h before sex (range 25–100 mg), at most once a day. PAH: 20 mg three times a day (up to 80 mg three times a day) |
| Time to peak | 30–120 min, median 60 min (fasted) |
| Half-life (label) | About 4 h, for both sildenafil and its active metabolite |
| Metabolism | Mainly CYP3A4, partly CYP2C9, in the liver |
| US status | Prescription only (Rx). In the UK, a 50 mg product (Viagra Connect) is a pharmacy medicine |
| WADA status | Not on the 2026 Prohibited List |
What it is
Sildenafil has the formula C₂₂H₃₀N₆O₄S and a molecular weight of 474.6 g/mol (PubChem). Tablets contain it as the citrate salt (molecular weight 666.7), in amounts equivalent to 25, 50 or 100 mg of sildenafil base (Viagra label).
It was made at Pfizer’s research center in Sandwich, UK, under the code UK-92,480. It was first developed as a possible treatment for angina, then redirected to ED, and later to pulmonary hypertension (Ghofrani et al., Nat Rev Drug Discov 2006). The first published pharmacology reported a PDE5 IC50 (the concentration that blocks half the enzyme’s activity) of 0.0039 µM, or 3.9 nM. In 12 men with ED without an established physical cause, it improved the duration and rigidity of erections in response to visual sexual stimulation (Boolell et al., Int J Impot Res 1996).
Mechanism
During sexual stimulation, nerves release nitric oxide in the erectile tissue. Nitric oxide raises cyclic GMP (cGMP) in smooth muscle cells, the muscle relaxes, and blood flows in. PDE5 is the enzyme that breaks cGMP down. Sildenafil blocks PDE5, so cGMP stays high for longer.
The label is explicit on two points: sildenafil has no direct relaxing effect on isolated human erectile tissue, and at recommended doses it has no effect without sexual stimulation. PDE5 is also found in platelets, vascular smooth muscle, skeletal muscle, the lungs and other organs. Its role in the lung’s blood vessels is the basis of the PAH use.
Selectivity
Sildenafil’s in-vitro selectivity for PDE5 over other phosphodiesterases, from the label:
| Enzyme | Main relevance | Selectivity for PDE5 over it |
|---|---|---|
| PDE6 | Retina (light signaling) | About 10-fold |
| PDE1 | Brain, heart, blood vessels | More than 80-fold |
| PDE3 | Heart muscle contraction | About 4,000-fold |
| PDE2, PDE4, PDE7–PDE11 | Various | More than 700-fold |
The low margin over PDE6 is thought to explain the transient color-vision changes seen at higher doses.
Sildenafil vs tadalafil
The two drugs share a mechanism and most warnings. They differ mainly in timing and selectivity (Viagra label; Cialis label):
| Feature | Sildenafil (Viagra) | Tadalafil (Cialis) |
|---|---|---|
| Terminal half-life | About 4 h | 17.5 h |
| Labeled window of effect | RigiScan effect up to 4 h, smaller than at 2 h | Improved erectile function up to 36 h |
| Effect of a high-fat meal | Peak delayed ≈ 60 min, peak level 29% lower | None |
| Selectivity over PDE6 (retina) | About 10-fold | 700-fold |
| Selectivity over PDE11 | More than 700-fold | 14- to 40-fold |
| Labeled ED regimens | As needed only | As needed, or 2.5–5 mg once daily |
| Other labeled uses | PAH (as Revatio) | BPH; PAH (as Adcirca) |
| Nitrates after a dose | Label says a safe interval is unknown | At least 48 h, under close supervision |
Pharmacokinetics
From the Viagra and Revatio labels (Viagra label; Revatio label):
| Parameter | Value |
|---|---|
| Absolute oral bioavailability | 41% on average (range 25–63%) |
| Time to peak (fasted) | 30–120 min, median 60 min |
| High-fat meal | Peak delayed ≈ 60 min; peak level 29% lower |
| Dose proportionality | Yes, over the 25–100 mg range |
| Volume of distribution | ≈ 105 L |
| Plasma protein binding | ≈ 96% (sildenafil and its main metabolite) |
| Metabolism | CYP3A4 (major) and CYP2C9 (minor), to N-desmethyl sildenafil |
| Active metabolite | About 50% of the parent’s PDE5 potency at ≈ 40% of its plasma level; accounts for ≈ 20% of the effect |
| Terminal half-life | About 4 h (sildenafil and metabolite) |
| Excretion | ≈ 80% in feces, ≈ 13% in urine, as metabolites |
| Plasma level after 100 mg | Peak ≈ 440 ng/mL; ≈ 2 ng/mL at 24 h |
Exposure is higher in several groups, which is why the label suggests considering a 25 mg starting dose for them:
| Group | Change in sildenafil exposure |
|---|---|
| Healthy men 65 and older | Total AUC +84% (unbound drug +45%) |
| Mild to moderate liver impairment (Child-Pugh A–B) | AUC +85%, peak +47% |
| Severe kidney impairment (creatinine clearance under 30 mL/min) | AUC and peak roughly doubled |
| Mild or moderate kidney impairment | Unchanged |
Less than 0.001% of a dose was estimated to appear in semen 90 minutes after dosing.
Approved medical use
Viagra is approved only for erectile dysfunction. It is not indicated for women or for anyone under 18 (Drugs@FDA, NDA 020895). The European Commission authorized it on September 14, 1998 (EMA).
Revatio is approved for PAH (WHO Group I) in adults, to improve exercise ability and delay clinical worsening, and in children aged 1–17 (Drugs@FDA, NDA 021845).
| Use | Labeled dose |
|---|---|
| ED (Viagra) | 50 mg about 1 h before sex (taken anywhere from 30 min to 4 h before); adjust to 25 or 100 mg. Not more than once per day |
| ED with an alpha-blocker, ritonavir or strong CYP3A4 inhibitors | Start at 25 mg; with ritonavir, no more than 25 mg in 48 h |
| PAH, adults (Revatio tablets or suspension) | 20 mg three times a day; may be raised to a maximum of 80 mg three times a day |
| PAH, adults (Revatio injection) | 10 mg intravenous bolus three times a day |
| PAH, children | 10 mg three times a day up to 20 kg; 20 mg three times a day above 20 kg; up to 40 mg three times a day above 45 kg |
In November 2017 the UK medicines regulator reclassified Viagra Connect (sildenafil 50 mg) from prescription-only to a pharmacy medicine for men over 18 with ED. It is sold after a discussion with a pharmacist and is not to be sold to men with severe cardiovascular disorders, high cardiovascular risk, liver failure, severe kidney failure or certain interacting medicines (MHRA 2017).
What the research shows
Erectile dysfunction
Sildenafil was evaluated in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in more than 3,000 men aged 19–87, and it beat placebo in all 21 (Viagra label).
The pivotal publication combined two trials (Goldstein et al., NEJM 1998):
- Dose-response trial (532 men, 24 weeks). Erectile function improved as the dose rose from 25 to 100 mg. On 100 mg, the mean score for achieving erections doubled, from 2.0 to 4.0 out of 5.
- Flexible-dose trial (329 men, 12 weeks). In the last 4 weeks, 69% of intercourse attempts succeeded on sildenafil vs 22% on placebo, or 5.9 vs 1.5 successful attempts per month.
- Open-label extension. 92% of the 225 men who entered it completed 32 more weeks.
In four fixed-dose trials (1,797 men, 12–24 weeks), the share reporting improved erections was:
| Arm | Reported improved erections |
|---|---|
| Placebo | 24% |
| Sildenafil 25 mg | 63% |
| Sildenafil 50 mg | 74% |
| Sildenafil 100 mg | 82% |
Diaries from about 1,600 men showed no change in how often men attempted sex (about twice a week). What changed was success: about 66% of attempts on sildenafil vs about 20% on placebo.
The label also reports results in harder-to-treat groups:
| Population | Improved erections, sildenafil vs placebo | Successful attempts, sildenafil vs placebo |
|---|---|---|
| Diabetes (n = 268) | 57% vs 10% | 48% vs 12% |
| Spinal cord injury (n = 178, crossover) | 83% vs 12% | 59% vs 13% |
| After radical prostatectomy (all trials) | 43% vs 15% | — |
| Psychogenic ED (subgroups, n = 328) | 84% vs 26% | 70% vs 29% (n = 178) |
How it compares with other PDE5 inhibitors
A network meta-analysis of 82 randomized trials (47,626 patients) compared the usual starting doses (Chen et al., Eur Urol 2015):
- sildenafil 50 mg had the greatest efficacy but also the highest overall rate of adverse events;
- tadalafil 10 mg had intermediate efficacy and the lowest overall rate of adverse events.
The choice between them is a trade-off between strength of effect, side effects and duration. The tadalafil page covers the long-acting alternative in detail.
Pulmonary arterial hypertension
The SUPER trial randomized 278 patients with symptomatic PAH to placebo or sildenafil 20, 40 or 80 mg three times a day for 12 weeks (Galiè et al., NEJM 2005):
| Dose (three times a day) | Placebo-corrected gain in 6-minute walk distance |
|---|---|
| 20 mg | 45 m (+13.0%) |
| 40 mg | 46 m (+13.3%) |
| 80 mg | 50 m (+14.7%) |
All three doses lowered pulmonary artery pressure and improved functional class, but clinical worsening did not differ from placebo over 12 weeks. The doses did not differ from each other, and the Revatio label notes no added benefit from doses above 20 mg three times a day in this trial.
In the PACES-1 trial, 267 patients already on intravenous epoprostenol received added sildenafil or placebo for 16 weeks. Walk distance improved by 26 m more on sildenafil (95% CI 10.8–41.2), and placebo patients were about 3 times more likely to have a clinical worsening event (Revatio label).
Exercise at altitude and at sea level
Because sildenafil dilates the lung’s blood vessels, it has been tested against the pulmonary hypertension caused by low oxygen:
| Study | Design | Main finding |
|---|---|---|
| Ghofrani et al., Ann Intern Med 2004 | 14 healthy mountaineers, 50 mg vs placebo, crossover; breathing 10% oxygen at low altitude, and at Mount Everest base camp | In hypoxia at low altitude, maximum workload 172.5 W vs 130.6 W. At base camp, higher maximum workload and cardiac output, lower lung artery pressure. Did not test normal oxygen |
| Hsu et al., J Appl Physiol 2006 | 10 trained men, 50 mg, 100 mg or placebo, cycling at sea level and at simulated 3,874 m | No effect on any measure at sea level. At simulated altitude, a 6-km time trial was 15% faster, driven by some “responders” |
About “pumps” and muscle growth. Sildenafil is sometimes promoted for muscle blood flow, “pumps” or performance. The one controlled trial in trained men at sea level found no effect on any cardiovascular or performance measure. The benefits seen were limited to low-oxygen conditions. No controlled human trial has shown that sildenafil increases muscle mass or strength.
A failed use in pregnancy
Sildenafil was tested as a way to improve placental blood flow in severe early-onset fetal growth restriction. The Dutch STRIDER trial randomized 216 pregnant women to 25 mg three times a day or placebo and was stopped early in 2018 (Pels et al., JAMA Netw Open 2020):
- the primary outcome (perinatal death or major neonatal illness) occurred in 60.2% on sildenafil vs 54.2% on placebo (RR 1.11, 95% CI 0.88–1.40);
- pulmonary hypertension in the newborn occurred in 18.8% vs 5.1% (RR 3.67, 95% CI 1.28–10.51).
The authors concluded that sildenafil did not help and may increase the risk of neonatal pulmonary hypertension.
Fertility
Single 100 mg doses had no effect on sperm motility or shape in healthy volunteers. In rats, doses producing more than 25 times human exposure did not impair fertility (Viagra label).
Side effects and risks
Common side effects
From the label’s fixed-dose phase II/III trials:
| Side effect | Placebo (n = 607) | 25 mg (n = 312) | 50 mg (n = 511) | 100 mg (n = 506) |
|---|---|---|---|---|
| Headache | 7% | 16% | 21% | 28% |
| Flushing | 2% | 10% | 19% | 18% |
| Dyspepsia (indigestion) | 2% | 3% | 9% | 17% |
| Abnormal vision | 1% | 1% | 2% | 11% |
| Nasal congestion | 2% | 4% | 4% | 9% |
| Back pain | 2% | 3% | 4% | 4% |
| Myalgia (muscle pain) | 1% | 2% | 2% | 4% |
| Dizziness | 2% | 3% | 4% | 3% |
Most side effects rise with dose. Even so, in placebo-controlled trials only 2.5% stopped sildenafil because of side effects, compared with 2.3% on placebo. In PAH patients, nosebleeds occurred in 13% of those whose PAH was linked to connective tissue disease.
Vision
The “abnormal vision” in trials was mostly a mild, transient color tinge, with some light sensitivity or blurring. At single doses of 100 and 200 mg, color discrimination (especially blue/green) was briefly impaired around the time of peak levels, consistent with PDE6 inhibition. Doses up to twice the maximum had no effect on visual acuity or eye pressure.
Sudden vision loss. Non-arteritic anterior ischemic optic neuropathy (NAION), a stroke of the optic nerve, has been reported rarely with all PDE5 inhibitors. Its background rate is 2.5–11.8 cases per 100,000 men aged 50 and older per year. Two observational studies cited on the label found roughly double the risk shortly after PDE5 inhibitor use (2.15, 95% CI 1.06–4.34; and 2.27, 95% CI 0.99–5.20), but the label states that a causal link has not been established. There are no controlled data in men with retinitis pigmentosa.
Nitrates and “poppers”: a dangerous combination
Sildenafil is contraindicated with any nitric oxide donor, regular or occasional. This includes nitroglycerin and other nitrates for angina, and the recreational “poppers” (such as amyl nitrite) named in the patient leaflet. The combination can drop blood pressure to unsafe levels.
Unlike the tadalafil label, the Viagra label does not give a safe waiting period. Plasma levels 24 hours after 100 mg are about 2 ng/mL, compared with a peak of about 440 ng/mL, but they are 3 to 8 times higher in older men, people with liver or severe kidney impairment, and those on CYP3A4 inhibitors. The label states that it is unknown whether nitrates can be given safely at 24 hours. Guanylate cyclase stimulators such as riociguat are also contraindicated.
Blood pressure, alpha-blockers and alcohol
On its own, a single 100 mg dose lowered sitting blood pressure by 8.3/5.3 mm Hg at most in healthy volunteers, with the largest drop 1–2 hours after dosing. The effect was similar at 25, 50 and 100 mg.
With the alpha-blocker doxazosin, three crossover studies in men with BPH found these placebo-subtracted maximum drops in systolic pressure:
| Sildenafil dose with doxazosin | Supine (95% CI) | Standing (95% CI) |
|---|---|---|
| 25 mg (n = 17) | 7.4 mm Hg (−0.9 to 15.7) | 6.0 mm Hg (−0.8 to 12.8) |
| 50 mg (n = 19) | 9.1 mm Hg (5.5–12.7) | 11.6 mm Hg (7.3–15.9) |
| 100 mg (n = 20) | 7.9 mm Hg (4.6–11.1) | 4.3 mm Hg (−1.8 to 10.3) |
Some men had symptomatic low blood pressure. In a first group of 4 men given 100 mg with doxazosin, one had postural hypotension lasting 8 hours, and the protocol dose was cut to 25 mg. The label therefore requires men to be stable on the alpha-blocker first and to start sildenafil at the lowest dose.
Other combinations from the label:
- Amlodipine (blood pressure drug) plus sildenafil 100 mg: an extra drop of 8/7 mm Hg.
- Alcohol (0.5 g/kg, blood alcohol ≈ 0.08%) plus sildenafil 50 mg: no added drop in blood pressure compared with alcohol alone. The 100 mg dose was not tested.
Heart conditions
Sexual activity carries some cardiac risk, and the label says sildenafil should not generally be used by men for whom sex is inadvisable. There are no controlled data in men with a heart attack, stroke or life-threatening arrhythmia in the past 6 months, resting blood pressure under 90/50 or over 170/110 mm Hg, heart failure, or unstable angina. Caution is advised with aortic stenosis and other outflow obstruction.
In a trial of 144 men with ED and exercise-limited stable angina, a single 100 mg dose did not shorten the time to limiting angina (423.6 vs 403.7 seconds on placebo). After marketing, heart attacks, sudden cardiac death, strokes and arrhythmias have been reported in temporal association with use, mostly in men with existing risk factors. The label states it is not possible to tell whether these were caused by sildenafil, by sexual activity or by underlying disease.
Priapism and hearing loss
- Priapism. Erections lasting more than 4 hours, and priapism (painful erections over 6 hours), have been reported infrequently. Untreated priapism can permanently damage erectile tissue. Caution is advised with penile deformities (including Peyronie’s disease) and with sickle cell anemia, multiple myeloma or leukemia.
- Sudden hearing loss, sometimes with tinnitus and dizziness, has been reported in temporal association with PDE5 inhibitors.
Interactions through CYP3A4
| Co-administered drug | Effect on sildenafil exposure |
|---|---|
| Ritonavir 500 mg twice daily | AUC about 11-fold higher; peak 4-fold higher; ≈ 200 ng/mL still present at 24 h |
| Saquinavir 1,200 mg three times daily | AUC +210%, peak +140% |
| Erythromycin 500 mg twice daily | AUC +182%, peak +160% |
| Cimetidine 800 mg | Plasma level +56% |
| Bosentan 125 mg twice daily (inducer) | AUC −63%, peak −55% |
Ketoconazole and itraconazole are expected to act at least as strongly as saquinavir, and strong inducers such as rifampin to lower levels further. Sildenafil itself is only a weak inhibitor of CYP enzymes and did not affect warfarin or tolbutamide. It did not add to aspirin’s effect on bleeding time.
High doses and overdose
Healthy volunteers given single doses up to 800 mg had the same kinds of side effects as at lower doses, but more often and more severely. Low blood pressure, fainting and prolonged erections were reported at 200–800 mg. Dialysis is not expected to help, because sildenafil is highly protein-bound.
Children with PAH
In the pediatric Revatio trials, deaths were more common at higher doses: 9.1% (5/55), 13.5% (10/74) and 22% (22/100) in the low-, medium- and high-dose groups. Deaths were attributed to PAH progression, and an adult study did not confirm the signal. The label caps the dose at 40 mg three times a day for children over 45 kg (Revatio label).
Who should not use it
The label contraindicates sildenafil in people who:
- use any nitric oxide donor (organic nitrates or nitrites), regularly or occasionally;
- use a guanylate cyclase stimulator such as riociguat;
- have a known hypersensitivity to sildenafil.
Combining Viagra with Revatio, another PDE5 inhibitor such as tadalafil, or other ED treatments has not been studied and is not recommended. Sildenafil offers no protection against sexually transmitted infections.
Use outside medicine
In a survey of 219 gym members in San Francisco, the 40 anabolic steroid users took far more performance drugs than non-users (8.7 vs 3.7 on average). Erectile dysfunction drugs, specifically tadalafil and sildenafil, were among the prescription drugs they were more likely to misuse (Ip et al., Res Social Adm Pharm 2019).
Sildenafil is not named on the WADA anti-doping list, so it is not prohibited in sport (WADA 2026 Prohibited List).
Sildenafil obtained outside a pharmacy carries its own risks:
- Hidden in supplements. Of 776 adulterated supplements flagged in FDA warnings from 2007 to 2016, 353 were marketed for sexual enhancement. Sildenafil was the most common hidden drug in that group, found in 166 of them (47.0%) (Tucker et al., JAMA Netw Open 2018).
- Counterfeits. ED drugs are a major target for counterfeiters. The UK regulator reported seizing more than £50 million of unlicensed and counterfeit ED medicines over five years (MHRA 2017).
- Unknown dose and hidden interactions. A man who does not know he is taking sildenafil cannot avoid the nitrate interaction, and the dose is not controlled.
Key takeaways
- A short-acting PDE5 inhibitor. The half-life is about 4 hours, so it is taken as needed about an hour before sex. Tadalafil lasts far longer.
- Works only with sexual stimulation. It amplifies the nitric oxide signal and does not cause erections on its own.
- Effective across many causes of ED. In fixed-dose trials, 63–82% reported improved erections vs 24% on placebo, including in men with diabetes and spinal cord injury.
- No proven performance or muscle benefit at sea level. Gains in trained men appeared only in low-oxygen conditions.
- Never combine with nitrates or poppers. The label gives no safe waiting interval. Alpha-blockers, other blood-pressure drugs and strong CYP3A4 inhibitors such as ritonavir also raise the risk.
- Headache, flushing and indigestion are typical. A transient color-vision change is far more common than with tadalafil (11% at 100 mg vs under 0.1% across tadalafil trials). Rare but serious events include priapism, sudden vision loss and sudden hearing loss.
Sources
- Pfizer / Viatris. Viagra (sildenafil citrate) tablets, prescribing information. DailyMed; Drugs@FDA, NDA 020895.
- Pfizer / Viatris. Revatio (sildenafil) tablets, oral suspension and injection, prescribing information. DailyMed; Drugs@FDA, NDA 021845.
- Eli Lilly and Company. Cialis (tadalafil) tablets, prescribing information. DailyMed.
- European Medicines Agency. Viagra: EPAR, marketing authorisation granted 14 September 1998. EMA.
- Medicines and Healthcare products Regulatory Agency. MHRA reclassifies Viagra Connect tablets to a Pharmacy medicine. November 28, 2017. GOV.UK.
- National Center for Biotechnology Information. Sildenafil, PubChem CID 135398744. PubChem.
- Boolell M, Allen MJ, Ballard SA, et al. Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction. Int J Impot Res. 1996;8(2):47–52. PubMed.
- Ghofrani HA, Osterloh IH, Grimminger F. Sildenafil: from angina to erectile dysfunction to pulmonary hypertension and beyond. Nat Rev Drug Discov. 2006;5(8):689–702. PubMed.
- Goldstein I, Lue TF, Padma-Nathan H, et al. Oral sildenafil in the treatment of erectile dysfunction. Sildenafil Study Group. N Engl J Med. 1998;338(20):1397–1404. PubMed.
- Chen L, Staubli SE, Schneider MP, et al. Phosphodiesterase 5 inhibitors for the treatment of erectile dysfunction: a trade-off network meta-analysis. Eur Urol. 2015;68(4):674–680. PubMed.
- Galiè N, Ghofrani HA, Torbicki A, et al. Sildenafil citrate therapy for pulmonary arterial hypertension. N Engl J Med. 2005;353(20):2148–2157. PubMed.
- Ghofrani HA, Reichenberger F, Kohstall MG, et al. Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest base camp: a randomized, double-blind, placebo-controlled crossover trial. Ann Intern Med. 2004;141(3):169–177. PubMed.
- Hsu AR, Barnholt KE, Grundmann NK, et al. Sildenafil improves cardiac output and exercise performance during acute hypoxia, but not normoxia. J Appl Physiol. 2006;100(6):2031–2040. PubMed.
- Pels A, Derks J, Elvan-Taspinar A, et al. Maternal sildenafil vs placebo in pregnant women with severe early-onset fetal growth restriction: a randomized clinical trial. JAMA Netw Open. 2020;3(6):e205323. PubMed.
- Ip EJ, Doroudgar S, Lau B, Barnett MJ. Anabolic steroid users’ misuse of non-traditional prescription drugs. Res Social Adm Pharm. 2019;15(8):949–952. PubMed.
- Tucker J, Fischer T, Upjohn L, et al. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open. 2018;1(6):e183337. PubMed.
- World Anti-Doping Agency. World Anti-Doping Code International Standard: Prohibited List 2026. WADA 2026 Prohibited List.