Fasted timing still sets the 50 mg sildenafil clock

Will a high-fat meal delay Viagra 50 mg?

On an empty stomach the usual 50 mg tablet peaks near one hour. After a steak-and-butter plate the same sildenafil (Viagra) 50 mg food delay on the label pushes the peak later - often toward two hours. Plan the meal or plan the attempt, not both at once. This ward card does not take an order.

What a generic sildenafil coupon is quoting

A coupon for AB-rated 50 mg citrate is a licensed fill after a prescription, not brand Viagra cash and not a no-Rx blister. The food-delay line stays on the generic. So does the nitrate stop. HPH lists published bands. We do not sell tablets.

August cash bands at four licensed counters

Walmart, Costco, Kroger, and Walgreens already post coupon or warehouse numbers in public tools. Figures below are August 2026 snapshots. Your ZIP moves the dollar. Confirm at the counter before you drive.

Sildenafil in Clinic: Default Fill, Narrow Job

Sildenafil was the first oral PDE5 inhibitor FDA approved for erectile dysfunction and it remains the economic anchor of the class — not because it outperforms every cousin on rigidity, but because cost, familiarity, and data depth keep it first on the shelf.

Most men who ask for help with erections still leave with sildenafil citrate unless insurance or preference pushes elsewhere. Generic pricing after patent expiry made it the formulary workhorse, and decades of post-marketing exposure give prescribers a comfort level newer agents cannot match.

Label check: what you are actually offering is narrower than the ad campaigns implied. You are not curing vasculopathy or fixing a hostile marriage. You are opening a pharmacologic window where cavernosal smooth muscle can stay relaxed if stimulation releases local nitric oxide. Severe neuropathy, cavernous nerve transection, or untreated hypogonism with absent libido shrinks that window — milligram escalation cannot rewrite upstream biology.

Revatio — sildenafil 20 mg three times daily for pulmonary arterial hypertension — shares the active moiety with Viagra but targets a different exposure profile. Pharmacy confusion between Revatio and Viagra has produced overdoses and hypotensive emergencies. Verify indication and strength on every fill, including silent generic swaps.

Stratify cardiovascular risk even when the patient says the visit is only about sex. Activity stresses the heart like moderate exertion. Stable coronary disease without nitrates is not an automatic stop; unstable angina, recent infarction, and decompensated heart failure mean hold the script until cardiology clears activity.

Trainees sometimes lump PDE5 inhibitors with other lifestyle prescriptions. These are vasodilators with repeatable failure modes: wrong meal timing, no arousal, drug interactions, progressive microvascular disease. Sildenafil remains the teaching reference because its food effect is the loudest in the class and its trial archive is the deepest.

Label check: step therapy often demands a documented sildenafil trial before long-acting branded agents. Annoying, but clinically fair: many men succeed at 50 or 100 mg once timing and expectations are corrected. Chart dose, meal context, and attempt count before you document class failure.

Counterfeit sildenafil from unregulated sellers still shows up in FDA warnings — inactive tablets, supratherapeutic doses, odd adulterants. AB-rated generics from licensed pharmacies are the baseline when cost drives the conversation.

Hypogonadal men with low testosterone and low desire may need restoration before sildenafil shines; rigidity can improve once libido returns. Do not start testosterone solely to rescue sildenafil nonresponse without biochemical deficiency — that path carries treatment risk without evidence.

Pelvic radiation for prostate or rectal cancer produces delayed ED through microvascular and nerve injury. Trial subsets included post-radiation men with lower success than pure vasculogenic cohorts. One failed tablet after radiation is not grounds for immediate escalation.

ED severity correlates with future cardiovascular events in observational data. The first PDE5 visit is a reasonable moment to revisit pressure, lipids, glucose, smoking, and activity — the endothelium is failing in more than one bed.

Primary psychogenic ED and performance anxiety still exist. Sildenafil can help when anxiety blocks arousal; it does not replace brief counseling or referral when spectatoring, trauma, or partner conflict drives the story.

Overnight call rarely starts sildenafil, but it often meets the man with chest pain who took sildenafil earlier. The team needs last PDE5 dose time before anyone reaches for nitroglycerin — document it on admission when you can.

Label check: warehouse and mail-order generics rotate manufacturers without telling you. Proactive counseling when pill appearance changes prevents nocebo dropout that looks like pharmacologic failure in the chart.

Extending cGMP — Not Starting It

Mechanism literacy blocks two errors: expecting spontaneous erections, and missing why nitrates plus PDE5 inhibitors are incompatible at the pathway level.

Label check: penile erection is hemodynamics: inflow rises, venous outflow gets trapped in the corpora. Stimulation activates neuronal and endothelial nitric oxide synthase; nitric oxide hits soluble guanylate cyclase and converts GTP to cyclic GMP.

PDE5 dominates corpus cavernosum tissue and hydrolyzes cGMP back to 5′-GMP, ending the signal. Sildenafil binds the PDE5 catalytic site with high affinity — Ki near 4 nM in biochemical work — slowing hydrolysis while nitric oxide is present.

Bedside line worth repeating: sildenafil extends an existing nitric oxide–cGMP signal. No stimulation, no meaningful cGMP pile-up, no erection. Men who take the pill and wait passively will report failure with intact pharmacology.

Isoform selectivity explains side effects better than brand names. PDE6 in retina gets inhibited at higher exposures — blue-tinted vision, light sensitivity. PDE1 and PDE11 cross-reactivity at higher concentrations is usually subtle at standard ED doses.

Elevated cGMP activates protein kinase G, lowers smooth-muscle calcium, dilates penile arterioles, expands trabeculae, engages veno-occlusive trapping. Systemic pressure falls modestly in normotensive volunteers — single-digit mmHg — dangerous only when other vasodilators stack on the same clock.

Label check: intracavernosal alprostadil skips the nitric oxide requirement via prostaglandin pathways. Refractory cases often combine oral PDE5 with injection or vacuum because each tool hits a different layer of the same hemodynamic goal.

Cavernous nerve injury lowers neuronal nitric oxide; endothelial dysfunction lowers eNOS output. Sildenafil cannot synthesize cGMP upstream — only prolong what was made. That ceiling explains weaker response after radical prostatectomy versus mild vasculogenic ED.

Riociguat stimulates guanylate cyclase while sildenafil blocks degradation — parallel logic to the nitrate ban with a different upstream trigger. Combined use is contraindicated.

Selectivity ratios versus other PDE isoforms predict the side-effect fingerprint: ~10-fold over PDE6 versus PDE5 at therapeutic concentrations, wider margins over PDE2, weaker over PDE1 and PDE11. You will not calculate these at bedside; they explain why visual symptoms cluster here.

Animal work suggests androgen modulation of PDE5 expression in corpus cavernosum. Hypogonadal men with symptomatic deficiency may respond poorly until testosterone is restored — check morning testosterone when libido is absent despite adequate dosing trials.

Label check: structural biology of PDE5 with bound inhibitors shows conformational states affecting dissociation kinetics. For sildenafil, functional duration tracks relatively short plasma half-life versus long-acting class members.

Direct ion channel activity at therapeutic concentrations is negligible. QT language that dominates vardenafil labeling is less prominent here; unstable cardiac disease still contraindicates activity, not just the molecule.

Gut to Cavernosa: PK That Moves Date Night

Oral sildenafil citrate absorbs fast when the stomach is not fighting a high-fat load. Median Tmax ~60 minutes fasting, commonly 30–120 minutes depending on gastric emptying and gut-wall CYP3A4.

Absolute bioavailability ~41% — first-pass gut and liver metabolism eats more than half the dose before systemic circulation. Potent CYP3A4 inhibitors collapse presystemic clearance; ritonavir is the extreme teaching case.

High-fat meals change the curve in ways patients feel. Labeling: ~60-minute Tmax delay, ~18% Cmax drop, ~29% AUC drop when fat supplies ≥57% of calories. Steak does not kill the drug — it often kills the timeline you promised.

Protein binding >96% to albumin and alpha-1-acid glycoprotein. Vd ~105 L. Hemodialysis does not meaningfully remove parent drug; severe renal impairment still warrants dose reduction as clearance shifts.

Major metabolite N-desmethylsildenafil retains ~50% parent PDE5 potency. When CYP3A4 is blocked, parent and metabolite accumulate — functional effect can outlast the 3–5 hour parent half-life on paper.

Terminal t½ 3–5 hours in healthy volunteers. Steady-state math applies to Revatio TID for PAH (~5 days to steady state), not PRN ED where each dose stands alone.

Age ≥65 raises AUC ~84% at the same milligram dose — clearance falls, not absorption. Label 25 mg start in elderly men is PK-driven, not ageism.

CYP2C9 contributes a minor route. Polypharmacy with multiple enzyme inhibitors still deserves conservative dosing when exposure surprises appear.

Population PK in FDA reviews flags weight and creatinine clearance as covariates for inter-individual variability. No routine TDM in ED — titrate by effect and tolerability.

Renal impairment doubled AUC at CrCl <30 mL/min without proportional efficacy gain — dose reduction beats unchanged milligrams. Hemodialysis needs no supplemental PRN dose after sessions for typical ED use.

Label check: pediatric PK exists under Revatio PAH labeling. Adolescent ED extrapolation is off-label — separate household PAH products from adult ED tablets.

Label check: smoking induces CYP modestly; quitting improves ED through vascular recovery more than any PK shift from nicotine. Counsel cessation before chasing higher doses in heavy smokers.

NEJM Endpoints and What They Mean at Follow-Up

Endpoints were patient-reported function and diaries, not surrogate hemodynamics alone — why IIEF and sexual encounter profile questions persist in urology research decades later.

FDA erectile dysfunction approval rested on randomized double-blind placebo-controlled parallel trials in mixed-etiology ED. Goldstein et al. published the landmark 24-week NEJM results in 1998.

Fixed doses 25, 50, or 100 mg or placebo ~1 hour before intended activity. All active doses beat placebo on IIEF erectile function domain and diary-documented successful penetration and intercourse.

Label check: dose response was clear. 100 mg delivered largest IIEF gains and highest intercourse rates — often >70% in mild-to-moderate organic ED — with more headache and flushing. Most of us start 50 mg and adjust after one or two real attempts rather than jump to max.

Vasculogenic ED responds when nitric oxide signaling is partially intact. Post-radical prostatectomy injury attenuates response — upstream signal is reduced. Diabetes sits mid-pack: still beats placebo, absolute success trails nondiabetic cohorts because microvascular and neuropathic damage coexist.

Onset in practice mirrors PK: 30–60 minutes fasted typical. Usable erectogenic window aligns with half-life plus metabolite contribution — commonly up to 4–5 hours. Shorter than tadalafil; enough when couples plan one encounter.

Open-label extensions to 2–3 years showed sustained benefit in responders without PDE5 downregulation tachyphylaxis. Apparent loss tracks worsening diabetes, new beta-blocker, depression, relationship stress more than receptor desensitization.

Meta-analyses at equipotent exposures show overlapping odds ratios for successful intercourse across PDE5 agents. Agent choice follows duration, food independence, side-effect timing, cost — not categorical sildenafil inferiority.

Secondary endpoints — intercourse satisfaction, orgasmic function, overall treatment satisfaction — favored active drug at 50 and 100 mg. Debated MCID on IIEF-EF often centers near 4–5 points; trial means exceeded that at effective doses.

Label check: sSRI-treated men entered trials with blunted baseline response. Sildenafil still beat placebo in those subsets; 100 mg was more often needed than in unmedicated cohorts.

Spinal cord injury with preserved reflexogenic erections sometimes responds when psychogenic pathways remain partially intact. Autonomic dysreflexia risk in high lesions needs rehab input separate from dosing.

FDA statistical reviews required penetration and completion for success — partial rigidity without penetration counted as failure, stricter than casual patient language.

Placebo response 20–30% on diary endpoints; psychogenic components and regression matter. Sildenafil separated consistently at 50 and 100 mg across programs enrolling >4000 randomized men.

Label check: avanafil and newer entrants used non-inferiority versus sildenafil — regulatory acceptance that class efficacy ceiling was largely set by 1998 data.

Milligrams, Meals, and the Once-Daily Ceiling

Standard starting dose for erectile dysfunction is 50 mg orally as needed once per 24 hours maximum. Increase to 100 mg if tolerated and insufficient; decrease to 25 mg if headache, flushing, or hypotension dominate the experience.

Label check: label-directed special populations start at 25 mg: age 65 and older, mild-to-moderate hepatic impairment (Child-Pugh class B), creatinine clearance below 30 mL/min, and co-administration with potent CYP3A4 inhibitors such as ketoconazole, itraconazole, or ritonavir.

Child-Pugh class C hepatic impairment lacks robust ED dose-finding data. Labeling recommends against routine ED use because exposure is unpredictable and hypotension risk rises without reliable benefit. Specialist acceptance of risk with close monitoring is not the same as standard outpatient prescribing.

Timing flexibility is official: 30 minutes to 4 hours before sexual activity. In practice, tell fasted patients to plan for about an hour; tell restaurant patients to plan for two hours or choose a lighter meal if spontaneity matters within the evening.

Daily sildenafil for ED is off-label. Some research protocols explored endothelial biomarkers with daily low dose, but standard care remains PRN. Doubling up after a failed attempt the same day is unsafe and ineffective — maximum frequency is once per 24 hours.

Never interchange Revatio 20 mg three times daily with Viagra 50–100 mg PRN. A man who swallows a 100 mg Viagra tablet believing it is his pulmonary dose receives five times the PAH unit dose in one swallow.

Splitting scored 100 mg generics to economize is common patient behavior. Counsel that halving for 50 mg trials is reasonable when tablets are scored; quartering for 25 mg pieces is imprecise and not label-endorsed.

Alcohol in moderation is not contraindicated, but intoxication impairs erectile performance independent of sildenafil and worsens orthostatic dizziness when combined with vasodilation.

Storage at controlled room temperature protects citrate salt stability. Bathroom humidity degrades tablets over months — a practical detail for men who keep pills above the shower.

Fixed-dose trials informed labeling ranges; flexible titration in clinic often outperforms rigid 50 mg initiation in men with partial response at first attempt. Re-trial on at least eight separate occasions at optimized dose is guideline-concordant before declaring oral therapy inadequate.

Pediatric accidental ingestion of a single adult tablet rarely causes prolonged priapism in prepubertal children but warrants poison control contact — distinct from therapeutic adolescent PAH use under specialist supervision.

Combinations That Can Kill or Spike Levels

Dangerous pairs are predictable from mechanism and metabolism — nitrates, strong CYP3A4 inhibitors, and riociguat belong on every med rec for men receiving PDE5 therapy.

Organic nitrates — nitroglycerin sublingual, isosorbide mononitrate, isosorbide dinitrate — are contraindicated. PDE5 inhibition prevents cGMP breakdown while nitrates drive cGMP synthesis through nitric oxide. Combined use can produce profound hypotension, syncope, myocardial ischemia, and death.

Label check: recreational nitrites, often called poppers, obey the same pharmacology with faster and less predictable kinetics. Ask directly during intake; men rarely volunteer inhalant use unprompted.

Label check: potent CYP3A4 inhibitors raise sildenafil AUC dramatically. Ritonavir-boosted regimens increased sildenafil AUC about 11-fold in interaction studies; maximum recommended ED dose with ritonavir is 25 mg no more than every 48 hours per label. Ketoconazole and itraconazole also require the 25 mg cap.

Label check: moderate inhibitors such as erythromycin or cimetidine warrant dose reduction and delayed side-effect counseling. Inducers including rifampin, carbamazepine, and St. John's wort may shorten the effective window by accelerating clearance — men on TB therapy sometimes report sudden treatment failure until rifampin stops.

Label check: alpha-1 blockers for benign prostatic hyperplasia or hypertension add orthostatic blood pressure reductions. Initiate sildenafil only after alpha-blocker dose is stable; start sildenafil at 25 mg when combining, especially with non-selective agents.

Label check: riociguat is contraindicated for parallel cGMP pathway elevation. Moderate alcohol may worsen vasodilation and orthostatic symptoms; heavy drinking impairs performance independent of drug pharmacokinetics.

HIV protease inhibitors beyond ritonavir vary in CYP3A4 inhibition potency — review each new antiretroviral against the sildenafil interaction table when treating men in HIV clinic.

Immunosuppressants tacrolimus and cyclosporine are CYP3A4 substrates with bidirectional interaction potential; transplant recipients needing sildenafil deserve pharmacist-led review of both drug levels and ED dose.

Isosorbide mononitrate for angina prophylaxis is contraindicated regardless of dosing schedule — sustained nitric oxide donor effect overlaps with sildenafil for the entire nitrate interval, not only the hour after a sublingual nitroglycerin tablet.

Doxazosin 4 mg daily plus sildenafil 50 mg produced greater standing blood pressure reductions than either alone in interaction studies. Tamsulosin 0.4 mg was somewhat better tolerated but still warrants 25 mg sildenafil start when combining.

Label check: antihypertensives generally add small mean blood pressure reductions that are clinically insignificant in most men but relevant in borderline hypotensive patients or those with autonomic neuropathy.

Vasodilation You Will Actually See

Headache, flushing, dyspepsia, nasal congestion, and dizziness head the phase III adverse event list. They correlate with peak plasma concentration and usually self-resolve within a few hours. Headache incidence rises from roughly 16% at 50 mg toward 28% at 100 mg in pooled data.

Visual changes — blue hue, increased light sensitivity, blurred vision — link to PDE6 inhibition in retina. They are typically transient. Sudden unilateral vision loss suggesting non-arteritic anterior ischemic optic neuropathy is rare but mandates immediate stop and urgent ophthalmology evaluation.

Sudden hearing decrease or tinnitus appears in post-marketing reports across PDE5 inhibitors as a class signal. Document onset timing; discontinue and refer to ENT for audiometry when symptoms are acute.

Priapism — painful erection beyond four hours — is uncommon, under 0.1% in trials, but urologic emergency. Sickle cell disease, multiple myeloma, and leukemia carry higher risk. Treat with aspiration, intracavernosal phenylephrine, and surgery if refractory.

Serious cardiovascular events in ED trials matched placebo among men cleared for sexual activity. Do not prescribe when sexual activity itself is contraindicated — severe unstable heart failure, recent stroke, uncontrolled hypertension.

Cutaneous serious reactions including Stevens-Johnson syndrome appear in FAERS databases. Stop the drug for progressive rash with mucosal involvement.

Facial flushing often peaks with Cmax and habituates in some men after three to five doses without dose change — distinguish tolerance from pharmacologic tachyphylaxis.

Dyspepsia may reflect lower esophageal sphincter relaxation; taking sildenafil with a small non-fatty snack sometimes helps men who get heartburn on empty stomach.

Syncope reports usually involve nitrates, alpha-blockers, or dehydration — reconstruct the timeline before blaming the PDE5 inhibitor alone.

Phase III pooled analysis reported dyspepsia in roughly 13% at 50 mg and 17% at 100 mg. Antacids do not prevent mechanism-based reflux symptoms; dose reduction often works better than acid suppression alone.

Non-arteritic anterior ischemic optic neuropathy post-marketing incidence remains debated; FDA added class warning without proving agent-specific causality — document visual acuity baseline if the patient has crowded optic disc.

Who Starts Lower and Why

Healthy elderly men aged 65 and older show about 84% higher plasma AUC at the same dose compared with younger volunteers because clearance falls. Starting at 25 mg reduces orthostatic symptoms while preserving efficacy in many.

Child-Pugh class B hepatic impairment: begin 25 mg. Class C: avoid routine ED dosing unless specialist accepts risk with close monitoring — label does not support standard use.

Creatinine clearance below 30 mL/min doubles AUC; 25 mg starting dose is mandated. Hemodialysis does not remove drug meaningfully; no supplemental dose after sessions for PRN use.

Diabetes mellitus is the most common comorbidity in ED clinics. Sildenafil remains statistically superior to placebo in diabetic subgroups, but nerve and microvascular damage lower absolute success rates. Optimize A1c, blood pressure, and lipids alongside the pill.

Post-prostatectomy patients use sildenafil in penile rehabilitation protocols to encourage perfusion during neuropraxia recovery. Expect lower rigidity scores than in pure vasculogenic ED; combination with devices or intracavernosal alprostadil is common in refractory cases.

Retinitis pigmentosa involves PDE6 pathway mutations; labeling lists relative contraindication. Shared decision-making with ophthalmology is reasonable when vision is already compromised.

Heart failure with preserved ejection fraction and borderline hypotension: start 25 mg and measure seated blood pressure before and two hours after first dose in clinic when feasible.

Kidney transplant recipients on sirolimus or everolimus need mTOR and CYP3A4 review; sildenafil is not contraindicated but exposure shifts warrant low starting dose.

Obesity correlates with ED severity and may alter distribution; efficacy trials included wide BMI ranges with dose titration still effective at 100 mg in many obese men.

Label check: sickle cell trait carries lower priapism risk than HbSS but is not zero — counsel all men with hemoglobinopathy before first prescription regardless of agent.

Chronic kidney disease stage 4–5 without dialysis: 25 mg start applies; men on nocturnal home dialysis have same protein binding considerations as in-center hemodialysis.

Scripts That Cut Callbacks

Most primary-care failures are timing, food, or expectation — not true pharmacologic nonresponse after adequate optimized trials.

Will it work if I am not in the mood? No — say it plainly on the after-visit summary so partners hear the same rule.

After dinner? Yes for sildenafil, but heavy fat pushes onset toward two hours. Light meal or empty stomach for the sixty-minute plan.

Nothing happened once? Retry four to eight separate attempts at optimized dose before class failure — one alcohol-heavy night does not count.

Chest pain after dose — EMS and ED must know PDE5 use within 24 hours before nitroglycerin. Wallet med lists with last dose time help.

Generic shape change? AB-rated, same rules — proactive mention when pharmacy rotates supplier prevents nocebo.

Partner thinks hours of constant erection? Clarify stimulation is required; priapism instructions in the same breath.

Generic as good as brand? Yes for AB-rated U.S. products — same meals, same nitrates, same stimulation requirement.

Can my partner take it? No FDA female indication — do not share prescription.

Admission for chest pain — ED meds vanish from hospital lists unless you document last dose.

Young men with performance anxiety may need brief CBT alongside pill — spectatoring does not dissolve at 100 mg alone.

Public formulary defaults to sildenafil — know Revatio/Viagra confusion when both NDCs share a contract.

Prescribing Checklist Before You Sign

Sildenafil remains a first-line PDE5 inhibitor with the deepest generic pricing and the most familiar patient name. Registration trial efficacy was dose-dependent on IIEF and intercourse success endpoints.

Mechanism requires sexual stimulation; the drug extends cGMP, it does not create erections de novo. High-fat meals delay absorption in a clinically obvious way that is unique within the class at this magnitude.

Contraindications are absolute for nitrates, nitrites, and riociguat. Strong CYP3A4 inhibitors cap dose at 25 mg. Alpha-blocker combinations need stable baseline dosing and cautious titration.

Start 50 mg PRN for most men; 25 mg for elderly, hepatic, renal, or interacting regimens; maximum 100 mg once daily. Duration of action roughly 4–5 hours — plan accordingly.

Side effects are vasodilatory and dose-related: headache, flushing, dyspepsia, visual symptoms. Priapism, sudden vision loss, and sudden hearing loss require urgent action though they are rare.

When sildenafil fails after adequate trials, switch agents or add second-line options — do not assume class failure until another PDE5 inhibitor is tested under appropriate conditions.

Label check: revatio and Viagra product confusion remains a medication safety priority — separate inventory in pharmacy and explicit indication documentation in e-prescribing.

Generic pricing makes sildenafil the cost-effective anchor; duration-limited window is acceptable when couples plan timing and avoid high-fat pre-coital meals.

The 1998 label established the template subsequent PDE5 inhibitors followed: IIEF-EF domain change, diary successful intercourse percentage, and safety monitoring for hypotension, vision, and priapism.

Label check: when a man asks whether sildenafil still works compared with newer agents, trial math says yes for most mild-to-moderate ED — differences show up in planning convenience and side-effect flavor, not a magic rigidity jump for the average patient.

Sildenafil citrate dissociates in gastric acid; film coating protects from light and moisture. Chewing tablets bypasses coating without improving absorption enough to matter — swallow whole with water.

Ritonavir 600 mg twice daily with sildenafil 25 mg produced Cmax and AUC increases consistent with near-complete loss of presystemic extraction — HIV clinic workflows should stock 25 mg sildenafil or defer elective ED treatment when boosted protease inhibitors cannot change.

Successful intercourse rates at 100 mg in pooled phase III analyses approached 80% in mild ED and 60% in moderate ED using strict diary definitions — numbers decline when patients remember only sometimes works without structured attempts.

N-desmethylsildenafil AUC increases disproportionately when CYP3A4 is blocked — effective functional half-life extends beyond parent 3–5 hours when the patient takes clarithromycin for COPD exacerbation.

Label check: exercise treadmill testing at 5–6 METs without angina remains practical standard before first PDE5 prescription in men with coronary disease risk factors — sildenafil does not substitute for that assessment.