What a 100 mg sildenafil tablet is used for
The uses question for Viagra is narrower than Cialis: one licensed ED claim on this brand, three tablet strengths, and a ceiling this page keeps in the title.
A 100 mg sildenafil tablet treats erectile dysfunction. That is the Viagra indication. It is not a daily prostate drug, and it is not the Revatio pulmonary brand even though the INN is the same. The ceiling dose exists because some men do not get a useful erection at 50 mg after a fair, fasted trial.
Pfizer's usual start is 50 mg, taken as needed about one hour before sexual activity, with a legal window from 30 minutes to 4 hours. The dose may rise to 100 mg or fall to 25 mg. Once per day is the frequency cap. See the dose overlay markup for the ladder and the meal markup for dinner timing.
Men who buy 100 mg as the first cheap generic strip because the number looks decisive skip the start that the label wrote for most patients. Side effects also rise at 100 mg in the fixed-dose tables - headache, flushing, dyspepsia, colour-tinge vision.
Medicines that force a 25 mg conversation
Alpha-blockers: the man should be stable on the blocker first; Viagra starts at 25 mg. In an early 100 mg plus doxazosin cohort, postural hypotension was ugly enough that the protocol dropped to 25 mg.
Erythromycin raised sildenafil Cmax 160% and AUC 182%. Saquinavir raised Cmax 140% and AUC 210%. Ketoconazole and itraconazole are expected to do at least as much. Consider 25 mg.
Ritonavir: 25 mg, and not again inside 48 hours. That sentence is stronger than 'consider.'
Amlodipine and other antihypertensives can add a small extra drop. The labelled drama is nitrates and alpha-blockers, not every blood-pressure tablet. Still list them all at the window.
Hearing, vision, and the four-hour rule
Stop sildenafil and get medical care if vision vanishes in one or both eyes. NAION is rare. A history of NAION in one eye raises the chance in the other. A crowded optic disc is the anatomic footnote the label keeps repeating.
Sudden hearing decrease belongs in the same stop list. Do not take the leftover 100 mg 'to see if it happens again.'
Four hours is the erection clock. Six hours is the painful-priapism language. Neither is a home experiment. Tell emergency staff the milligram and the clock time. If you also took a nitrate or a second PDE5, say that first.
Erectile use, not the pulmonary brand
Revatio sildenafil for pulmonary arterial hypertension uses a different dose rhythm - typically 20 mg three times daily in the PAH label world - and a different clinic. Do not swallow three Viagra 100 mg tablets to invent a pulmonary regimen, and do not treat a 20 mg Revatio tablet as a low-dose ED starter without the prescriber saying so.
The chemistry is sildenafil citrate either way. The use is not. Filing both brands on one home blister is how double-dosing happens.
Female sexual dysfunction is not a Viagra indication. Off-label curiosity does not belong on this uses sheet.
Who must not take this use
Organic nitrates and organic nitrites in any form. Sildenafil was shown to potentiate their hypotensive effect. The label does not give a safe hour when nitrates can be added after a dose, even though plasma at 24 hours is far below peak.
Riociguat. Known hypersensitivity to sildenafil or a tablet excipient.
Sexual activity that is already unsafe because of cardiovascular status. The tablet treats the erection, not the ischaemic risk of the encounter.
Prior NAION, a crowded disc, and anatomical or haematological priapism risk need a named benefit-risk talk. Sudden vision or hearing loss after a dose is a stop-and-seek-care event, not a 'maybe the next 100 mg.'
Stops on a 100 mg evening
- Nitrates, nitrites, poppers - contraindication
- Riociguat - contraindication
- Unstable cardiac status for sex - do not use the tablet to override it
- Erection >4 hours - emergency (144 if collapsing)
- Second PDE5 the same day - not a use, a stack
The 25-50-100 ladder and this ceiling lock
25 mg is the start this label wants in older men, in severe renal impairment (CrCl under 30 mL/min), in hepatic impairment, with alpha-blockers, and with several CYP3A4 inhibitors. It is also the step-down when 50 mg works but hurts.
50 mg is the recommended dose for most patients. Skipping it because a website sold only 100 mg strips is a procurement habit, not pharmacology.
100 mg is the maximum recommended dose and the lock on this page. It is once daily. It is not a second tablet at midnight after the first 100 mg disappointed you at 22:00.
Ritonavir is the extreme interaction: sildenafil AUC rose 11-fold. The labelled maximum is then 25 mg in a 48-hour period. A 100 mg ceiling lock does not apply to that man.
| Patient | Usual labelled start | Ceiling |
|---|---|---|
| Most adults | 50 mg PRN | 100 mg once daily |
| Age over 65, severe renal, hepatic impairment | Consider 25 mg | Prescriber call |
| On an alpha-blocker, already stable | 25 mg | Titrate if watched |
| Erythromycin or strong CYP3A4 inhibitor | Consider 25 mg | Not automatic 100 |
| Ritonavir | 25 mg; max 25 mg / 48 h | 100 mg forbidden by the cap |
What the 100 mg studies actually measured
Eight double-blind crossover studies used RigiScan hardness and duration after sexual stimulation. Most looks sat near 60 minutes. Effect ran to 4 hours and was already weaker at 4 hours than at 2 hours. That is the short-evening use in a number, not a slogan.
A single 100 mg dose in healthy volunteers dropped sitting blood pressure by a mean maximum of 8.3/5.3 mm Hg, clearest at 1-2 hours, gone versus placebo by 8 hours. Inside 25-100 mg the pressure effect did not climb with the milligram. Nitrate co-administration is the exception that makes the drop dangerous.
Peak plasma after 100 mg in healthy men is about 440 ng/mL. At 24 hours the same story is about 2 ng/mL. Older men, hepatic impairment, CrCl under 30 mL/min, and strong CYP3A4 inhibitors keep 3 to 8 times more drug at that 24-hour mark. The label still will not name a safe hour for a nitrate.
Common trial events at or above 2% include headache, flushing, dyspepsia, abnormal vision, nasal congestion, back pain, myalgia, nausea, dizziness, and rash. Colour-tinge vision is the row patients remember at 100 mg. It is not NAION. Sudden field loss is.
Age, kidney, liver, and why 25 mg keeps coming back
Age over 65, any studied hepatic impairment, and CrCl under 30 mL/min all raise sildenafil exposure. The labelled move is to consider 25 mg first. Mild and moderate renal impairment (CrCl 30-80) do not get an automatic cut.
Child-Pugh A and B volunteers showed about 47% higher Cmax and 85% higher AUC. Child-Pugh C was not studied. 'A bit of cirrhosis' is still a 25 mg conversation.
Severe renal impairment roughly doubled Cmax and AUC. That man is not a casual 100 mg ceiling candidate on night one.
Counterfeit blue diamonds in travel retail are not Pfizer VGR100 stock. A cheap online 100 mg that arrived without a batch story is not this uses sheet. Geneva windows can name a generic with an MA. Airport kiosks cannot.
The once-a-day cap and the midnight second tablet
The frequency cap is once per day. A 100 mg tablet at 20:00 that disappointed at 23:00 does not become a 200 mg night. The short half-life tempts that error because the man feels 'empty' while plasma is still there.
If the first 100 mg was swallowed after a heavy meal, the honest retry is another evening, fasted or at least not after fondue - not a second tablet after midnight. See the meal markup.
Grapefruit and erythromycin are milder than ritonavir and still reason to stay off a casual 100 mg ceiling. List the antibiotics. List the azoles. The 25 mg start exists for those lists.
A man who needs two encounters in one calendar day is looking at tadalafil's labelled window or at daily 5 mg, not at two sildenafil ceilings. That is a switch conversation on the overlay, after a gap.
Why dinner moves the 100 mg peak
In the fasted state, maximum plasma levels arrive between 30 and 120 minutes, median 60 minutes. That is why the counselling line is 'about an hour,' not 'with the first course.'
When Viagra is taken with a high-fat meal, Tmax slips by a mean of 60 minutes and Cmax falls by a mean of 29%. The label still permits food. The practical uses note is that a fondue-heavy evening makes a 100 mg tablet look like a late, weaker tablet.
Men who declare 100 mg a failure after a steak-and-wine night have often tested the meal, not the molecule. Repeat the same milligram fasted before you escalate folklore or hop to another PDE5 column on the overlay.
Absolute bioavailability is 41% (range 25-63%). That number is about first-pass metabolism, not about whether you ate bread.
Effects that show up more at 100 mg
In the fixed-dose Phase II/III tables, headache, flushing, dyspepsia, nasal congestion, and abnormal vision were more common on sildenafil than placebo, and several of those rows climb from 25 to 100 mg. Colour-tinge vision is the PDE6 fingerprint patients remember.
Dizziness and a faint feeling after a large wine pour plus 100 mg is a vasodilation stack, not an allergy. Lie flat. If the man is unresponsive or chest pain starts, 144.
Priapism is infrequent in post-marketing counts and still sits in counselling because delay costs tissue. Hearing drop is uncommon and still a same-day stop.
A 100 mg tablet does not cause a 36-hour hangover the way tadalafil PRN can. The short half-life is why some men prefer this use and why others call it a timer pill.
Where a 100 mg fill is quoted
The quote block below is a dated GoodRx pair for generic sildenafil 100 mg, ten tablets - the ceiling lock - not a 25 mg or 50 mg board. Yvessa does not dispense. Each pharmacy name is that chain's page.
Food still pushes the peak after you pay. A cheap fill that is swallowed after a heavy dinner is a late fill.
Corrections: [email protected]. Prescriptions: your clinician. Swiss emergency: 144.
Generic sildenafil 100 mg, ten tablets, is the Yvessa Viagra ceiling lock, 21 August 2026. GoodRx lists 100 mg x 10 at $201.93 / $10.62. Food still pushes the peak. Twenty-five and fifty milligram boards live on other plans. Yvessa does not dispense.
How sildenafil holds cGMP for a short evening
The mechanism is the class mechanism: NO, guanylate cyclase, cGMP, cavernosal relaxation. Sildenafil blocks PDE5 so cGMP lasts longer. Arousal still has to open the NO tap.
Parent drug and the N-desmethyl metabolite both have terminal half-lives of about 4 hours. The metabolite keeps roughly half the PDE5 potency of the parent. The useful erectile window in RigiScan work ran to 4 hours and was already weaker at 4 hours than at 2 hours.
PDE6 in the retina is the reason colour-tinge reports are more familiar with sildenafil than with tadalafil at usual ED doses. Class NAION language still sits on the label.
A single 100 mg dose in healthy volunteers dropped sitting blood pressure by a mean maximum of 8.3/5.3 mm Hg, most notable at 1-2 hours, gone versus placebo by 8 hours. Inside 25-100 mg the pressure effect did not climb with the milligram. Nitrate co-administration is the exception that makes the drop dangerous.
| Absorption | Oral bioavailability 41% (25-63%). Fasted Tmax 30-120 min, median 60. High-fat: Tmax +60 min, Cmax -29%. |
|---|---|
| Distribution | Vss 105 L; sildenafil and N-desmethyl metabolite ~96% protein bound. |
| Metabolism | Hepatic, mainly CYP3A4, minor CYP2C9, to an active N-desmethyl metabolite (~50% PDE5 potency). |
| Excretion | T1/2 about 4 h for parent and metabolite. Feces ~80%, urine ~13%. |
What this ceiling-use sheet leaves open
The locked use is 100 mg sildenafil as the labelled ED ceiling, taken once a day, with food allowed and a high-fat meal still delaying the peak. Most men should have a 50 mg chapter first unless a labelled special population says 25 mg.
Revatio is a different use. Daily tadalafil is a different clock - see the tadalafil uses plan. Vardenafil 10 mg is a different potency number - see the vardenafil uses plan.
Dose changes go through a prescriber or pharmacist. 144 for collapse, chest pain, priapism past four hours, or sudden vision or hearing loss. Reviewed 21 August 2026.
Sources
- DailyMed Viagra (sildenafil citrate) - indication, 50 mg start, 100 mg ceiling, food, ritonavir 25 mg / 48 h.
- Pfizer Viagra US PI clinical pharmacology - bioavailability 41%, high-fat Tmax +60 min / Cmax -29%, t1/2 ~4 h, 100 mg BP 8.3/5.3 mm Hg.
- Yvessa PDE5 overlay - meal and clock compare.
- Meal markup and dose overlay markup.
Checked against the current label and reviewed by Dr. Amélie Laurent. See Survey, Draft, Peer-check, Stamp.
