Does food stop Viagra from working?

No label says so, and all four permit food outright — "VIAGRA may be taken with or without food." What the sildenafil label reports is a change in absorption rather than in effect: "When VIAGRA is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%." That moves the median time to peak concentration from 1 hr to 2 hr and lowers the peak by 29%. The label's own patient leaflet puts it as "VIAGRA can be taken with or without food. If you take VIAGRA after a high fat meal (such as a cheeseburger and french fries), VIAGRA may take a little longer to start working" — qualitatively, with no number, which is as far as the label goes and as far as this page goes.

Which ED medication is not affected by food?

Tadalafil, and it is the only one of the four. Its label states it flatly: "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food." The other three all report something. Sildenafil: a mean delay in Tmax of 60 minutes and a 29% fall in peak concentration with a high-fat meal. Avanafil: a delay of 1.12 to 1.25 hours and a 39% fall at 200 mg, which its label calls "of minimal clinical significance". Vardenafil: a fall in peak concentration of 18% to 50%, with no delay to the peak stated at all.

How long before eating should I take an ED tablet?

No label answers this, and the honest answer is that the question does not have a labelled form. Each of the four gives exactly one food figure — for a high-fat meal taken with the dose — and none of them models what happens if the tablet is swallowed two hours after eating, or four. A curve between "with a meal" and "fasted" would be invented rather than sourced, so this page gives the two states the labels give and nothing between them. What the labels do say, all four of them, is that the tablet may be taken with or without food.

Can I drink alcohol with Viagra or Cialis?

The labels do not agree, which is itself the answer. Tadalafil warns at 5 units or greater — "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., 5 units or greater) in combination with CIALIS can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" — and tells patients "Do not drink too much alcohol when taking CIALIS (for example, 5 glasses of wine or 5 shots of whiskey)." Avanafil warns two units lower and tells patients "Do not drink too much alcohol when taking STENDRA (for example, 3 glasses of wine, or 3 shots of whiskey)." The sildenafil and vardenafil labels name no threshold and say nothing about alcohol to the patient; each reports one interaction study at 0.5 g/kg finding no potentiation of the hypotensive effect. Two of the four labels name a number of units and two name none. A label that says nothing about how much alcohol is too much is not saying that any amount is safe — it is a label whose sponsor ran one interaction study at one alcohol dose and reported the result. The sildenafil label attaches its own caveat to that result: the 100 mg dose, its own maximum, was not the dose tested. These are prescription medicines and the question belongs with the clinician who prescribed one.

How much alcohol is too much with tadalafil?

The CIALIS label names a figure and this page will quote it rather than interpret it: "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., 5 units or greater) in combination with CIALIS can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" Its pharmacology section shows the effect is dose-dependent. At 0.7 g/kg — about 6 ounces of 80-proof vodka in an 80 kg man — "In these two studies, more patients had clinically significant decreases in blood pressure on the combination of tadalafil and alcohol as compared to alcohol alone. Some subjects reported postural dizziness, and orthostatic hypotension was observed in some subjects." At 0.6 g/kg, roughly 4 ounces, "When tadalafil 20 mg was administered with a lower dose of alcohol (0.6 g/kg, which is equivalent to approximately 4 ounces of 80-proof vodka, administered in less than 10 minutes), orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated." So the label describes a threshold effect around a specific quantity, not a linear one, and it describes it in healthy volunteers rather than in men on blood pressure medication.

Does grapefruit juice interact with ED medication?

Three of the four labels say it probably does and not one of them says by how much. Tadalafil: "Although specific interactions have not been studied, other CYP3A4 inhibitors, such as erythromycin, itraconazole, and grapefruit juice, would likely increase tadalafil exposure." Vardenafil and avanafil carry the same construction in their own section 7.2. The sildenafil label does not mention grapefruit anywhere. All three of the sentences hedge identically — the interaction "has not been studied" and would "likely" increase exposure — so no percentage, no dose cap and no avoidance instruction exists on any of them to quote. The pharmaceutical CYP3A4 inhibitors named in the same sentences do come with caps; grapefruit does not.

Is a delay in Tmax the same as a delay in when it starts working?

No, and conflating the two is the commonest error on this subject. Tmax is the time at which plasma concentration is highest. A drug is generally doing something well before its peak and continues after it — sildenafil's own label documents an effect out to 4 hours while its median Tmax is 1 hour. No US PDE5 label states an onset of action as a time at all. Three of them give a lead time in the dosage section — approximately 1 hour, approximately 60 minutes, as early as approximately 15 minutes — and those are instructions about when to swallow the tablet, not measurements of when it begins to act. Tadalafil gives no lead time whatsoever, only "prior to anticipated sexual activity".

Did the trials these drugs were approved on control for food and alcohol?

Two of the four labels say in terms that they did not. Section 14 of the tadalafil label, describing both the as-needed and the once-daily programmes: "Food and alcohol intake were not restricted." Section 14 of the avanafil label, describing its four pivotal studies: "Food and alcohol intake was not restricted." That cuts both ways and the page states both. The efficacy those two drugs are licensed on was produced by men eating and drinking normally, which is reassuring. It also means the trials were not designed to measure what food or alcohol did, so they cannot be cited as evidence that neither matters.

ED medication, food and alcohol

Why “can be taken with food” answers a different question

Every one of the four labels has a short section headed Use with Food, and every one of them says the same thing. Sildenafil: "VIAGRA may be taken with or without food." Vardenafil: "Vardenafil tablets can be taken with or without food." Avanafil: "STENDRA may be taken with or without food." Tadalafil: "CIALIS may be taken without regard to food." Four labels, one instruction, and it is an instruction about permission — whether the tablet may be given with a meal. It is not a statement about what a meal does to the absorption, and those are different questions with four different answers.

Read the pharmacokinetics sections and they separate. Sildenafil is the most affected: "When VIAGRA is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%." Avanafil's peak is pushed back further still but its label calls the change trivial: "When STENDRA (200 mg) is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 1.12 to 1.25 hours and a mean reduction in Cmax of 39% (200 mg). There was an approximate 3.8% decrease in AUC. The small changes in avanafil Cmax and AUC are considered of minimal clinical significance; therefore, STENDRA may be administered with or without food." Vardenafil publishes a fall in peak concentration and, unusually, no delay at all: "Two food-effect studies were conducted which showed that high-fat meals caused a reduction in Cmax by 18% to 50%." And tadalafil is the exception in the other direction: "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food." So the ranking a reader wants — which one does dinner ruin — is sildenafil and avanafil at the top, vardenafil somewhere unmeasured in the middle, tadalafil not at all.

Here is the part that has to be said before any of those numbers is used, and it is the reason this page exists rather than a simple table. No US PDE5 label states an onset of action as a time. Three of the four give a lead time in the dosage section — "approximately 1 hour", "approximately 60 minutes", "as early as approximately 15 minutes" — and those are instructions about when to swallow the tablet, not measurements of when it starts working. Tadalafil gives no lead time at all, only "prior to anticipated sexual activity". Every time-to-peak figure on this page is a Tmax: the moment plasma concentration is highest, which is a different quantity and usually a later one. A high-fat meal moving sildenafil's median Tmax from 1 hr to 2 hr does not mean the tablet "starts working an hour later". It means the blood level peaks an hour later. The only translation of that into patient language on any of the four labels is on the sildenafil leaflet, and it is deliberately vague: "VIAGRA can be taken with or without food. If you take VIAGRA after a high fat meal (such as a cheeseburger and french fries), VIAGRA may take a little longer to start working". "A little longer" is as precise as an FDA-approved patient leaflet is prepared to be, and this page is not going to be more precise than the label.

One refinement while we are being careful about onset. The avanafil label does contain the phrase — section 14 describes a trial in which "Subjects were encouraged to attempt intercourse approximately 15 minutes after dosing and used a stopwatch for measurement of time to onset of effect, defined as the time to the first occurrence of an erection sufficient for sexual intercourse." It is still not an onset figure: the label reports the percentage of attempts that succeeded at about fifteen minutes, not a time. So the accurate version of the claim is that no label states an onset as a time, and one label studied the question and answered it as a success rate.

Alcohol is the other half of what people actually want to know, and here the four labels genuinely disagree rather than merely differing in emphasis. Tadalafil has a warnings section of its own: "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., 5 units or greater) in combination with CIALIS can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" Avanafil has one too, with a different number: "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., greater than 3 units) in combination with STENDRA may increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" Two labels, 3 units and 5 units, for the same kind of statement. The sildenafil and vardenafil labels have no warnings-section entry on alcohol at all, no unit threshold, and nothing about alcohol in their patient leaflets; what they have is an interaction study each, both finding no potentiation at 0.5 g/kg. Two of the four labels name a number of units and two name none. A label that says nothing about how much alcohol is too much is not saying that any amount is safe — it is a label whose sponsor ran one interaction study at one alcohol dose and reported the result. The sildenafil label attaches its own caveat to that result: the 100 mg dose, its own maximum, was not the dose tested.

Two sentences stop that becoming a simple ranking. The tadalafil finding is dose-dependent, not absolute — at 0.7 g/kg orthostatic hypotension was observed, and "When tadalafil 20 mg was administered with a lower dose of alcohol (0.6 g/kg, which is equivalent to approximately 4 ounces of 80-proof vodka, administered in less than 10 minutes), orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated." And the sildenafil label undercuts its own reassurance in the same paragraph: "The maximum recommended dose of 100 mg sildenafil was not evaluated in this study". The study used 50 mg. The label's maximum is 100 mg. Finally, grapefruit juice: avanafil, vardenafil and tadalafil all name it as a likely CYP3A4 inhibitor and the sildenafil label does not mention it at all — and not one of the three attaches a figure to it.

The formula

fasted peak window = the label’s own time-to-peak range

fed peak window = fasted window + the label’s stated mean

delay in Tmax with a high-fat meal

where the label states no delay → no fed window is computed

where the label states no effect → fed window = fasted window

Tmax ≠ onset. No term above is a time the drug starts working,

because no label states one.

There is deliberately no term for hours since the meal. Each label gives one figure, for a high-fat meal taken with the dose; none of the four models how that effect decays if the tablet is swallowed two or four hours after eating. A curve fitted between "with a meal" and "fasted" would be an invention, so this page gives two states and refuses the continuum between them.

Worked example

Sildenafil 50 mg, planned for an evening that includes dinner:

Fasted, the label puts the peak at 30 min – 2 hr, median 1 hr: "Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state."
With a high-fat meal the label adds 1 hr and takes peak concentration down 29% off the peak.
So the fed peak window is 1 hr 30 min – 3 hr, median 2 hr — the arithmetic is addition and nothing more.
What that does NOT say: that the tablet starts working an hour later, or that it works less well. The label's own patient translation is "VIAGRA can be taken with or without food. If you take VIAGRA after a high fat meal (such as a cheeseburger and french fries), VIAGRA may take a little longer to start working", and its dosage section still permits the meal outright.
The same evening on tadalafil changes nothing at all — "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food." — and on vardenafil the peak is cut by 18% to 50% with no delay stated, so there is no fed window to compute.
On avanafil the fasted peak is 30 min – 45 min and the fed peak 1 hr 42 min – 1 hr 57 min, a change its own label calls "of minimal clinical significance". And if the dinner comes with 5 or more drinks, the relevant sentence is no longer the food one — it is the alcohol section, which differs by drug and by 2 units between the two labels that give a number.

All four labels permit food — and all four report something different

The left column is the dosage instruction, which is effectively identical across the four. The right column is what the same label then says in its pharmacokinetics section.

Drug	What the dosage section says	Section	What the pharmacokinetics section then reports
avanafilStendra	“STENDRA may be taken with or without food.”	2.2	A high-fat meal delays the peak by about 1 hour; the label calls the change clinically minimal.
sildenafilViagra	“VIAGRA may be taken with or without food.”	2.2	A high-fat meal pushes the peak back a full hour and cuts it by 29% — the largest food effect of the four.
vardenafilLevitra	“Vardenafil tablets can be taken with or without food.”	2.2	A high-fat meal cuts the peak by 18–50%. No delay to the peak is stated.
tadalafilCialis	“CIALIS may be taken without regard to food.”	2.5	Absorption not influenced by food at all

Permission and pharmacokinetics are two different statements and only one of them is about your evening. Tadalafil is the only drug of the four for which they agree completely: "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food." For the other three the dosage section says food is allowed and the pharmacokinetics section says food changes the absorption — which is not a contradiction, because a change in absorption is not the same as a change in whether the drug may be given.

Time to peak concentration — fasted against after a high-fat meal

Computed by adding each label’s own stated delay to its own fasted range. This is a peak plasma concentration, not a time the drug starts working — no label states one of those.

Drug	Fastedlabel range	Medianwhere the label gives one	Delay with a high-fat meal	After a high-fat mealcomputed	Peak concentration change
avanafilStendra	30 min – 45 min	Given as a range	+ 1 hr 12 min	1 hr 42 min – 1 hr 57 min	peak concentration down 39% at 200 mg
sildenafilViagra	30 min – 2 hr	1 hr	+ 1 hr	1 hr 30 min – 3 hr	peak concentration down 29%
tadalafilCialis	30 min – 6 hr	2 hr	None — statedlabel says absorption is unaffected	30 min – 6 hr	No change stated
vardenafilLevitra	30 min – 2 hr	1 hr	Not statedlabel reports no Tmax delay	Not statedcannot be computed	peak concentration down 18–50%

The vardenafil row is the one worth pausing on. Its label reports a reduction in peak concentration of 18% to 50% with high-fat meals and states no delay to the peak at all, so the fed column is empty rather than filled with a figure borrowed from one of the other three. Avanafil's label gives its delay as a range — "a mean delay in Tmax of 1.12 to 1.25 hours" — and the 1 hr 12 min used in the arithmetic above sits inside it. The same avanafil label calls its own food effect "of minimal clinical significance".

Alcohol — what each label actually says

Two of the four warn at a named number of units and the two numbers are not the same. The other two name none, which is not the same as saying there is no limit.

Drug	Warns at	Warnings section	What the label’s own study found	What the patient leaflet says
avanafilStendra	3 units	5.7 Alcohol	Warns above 3 units; an extra 3.5/4.5 mmHg fall at 0.5 g/kg.12.2 Pharmacodynamics	“Do not drink too much alcohol when taking STENDRA (for example, 3 glasses of wine, or 3 shots of whiskey).”
sildenafilViagra	No threshold namedsilence, not permission	None	No potentiation at 0.5 g/kg. No threshold named, no leaflet line.7.5 Alcohol	Nothing about alcohol
vardenafilLevitra	No threshold namedsilence, not permission	None	No potentiation at 0.5 g/kg, over a 4-hour observation only.7.1 Potential for Pharmacodynamic Interactions with Vardenafil	Nothing about alcohol
tadalafilCialis	5 units	5.9 Alcohol	Warns at 5 units or more; orthostatic hypotension seen at 0.7 g/kg, not at 0.6.12.2 Pharmacodynamics	“Do not drink too much alcohol when taking CIALIS (for example, 5 glasses of wine or 5 shots of whiskey).”

The two labels that name a number disagree by 2 units — 3 on the avanafil label against 5 on the tadalafil label — for the same kind of statement about the same class of drug. Two of the four labels name a number of units and two name none. A label that says nothing about how much alcohol is too much is not saying that any amount is safe — it is a label whose sponsor ran one interaction study at one alcohol dose and reported the result. The sildenafil label attaches its own caveat to that result: the 100 mg dose, its own maximum, was not the dose tested. Two further sentences belong beside this table. The tadalafil effect is dose-dependent rather than absolute: "When tadalafil 20 mg was administered with a lower dose of alcohol (0.6 g/kg, which is equivalent to approximately 4 ounces of 80-proof vodka, administered in less than 10 minutes), orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated." And the reassuring sildenafil result carries the label's own caveat: "The maximum recommended dose of 100 mg sildenafil was not evaluated in this study" — the dose tested was 50 mg, not the 100 mg maximum.

Grapefruit juice — named on three labels, measured on none

The only food other than a high-fat meal that any of the four labels names. Every one of the three that names it hedges in the same way.

Drug	Named on the label?	What it says	How much it changes exposure
avanafilStendra	Yes — 7.2	“Although specific interactions have not been studied, other CYP3A4 inhibitors, including grapefruit juice are likely to increase avanafil exposure.”	No figure given
sildenafilViagra	No — not mentioned at all	The label does not name grapefruit anywhere	No figure given
vardenafilLevitra	Yes — 7.2	“Although specific interactions have not been studied, other CYP3A4 inhibitors, including grapefruit juice would likely increase vardenafil exposure.”	No figure given
tadalafilCialis	Yes — 7.2	“Although specific interactions have not been studied, other CYP3A4 inhibitors, such as erythromycin, itraconazole, and grapefruit juice, would likely increase tadalafil exposure.”	No figure given

Three of the four labels name grapefruit juice, and all three name it in the same hedged sentence: interactions with it "have not been studied" and it "would likely" increase exposure. Not one of them gives a figure — no percentage change in Cmax, no change in AUC, no dose adjustment. The sildenafil label does not mention grapefruit at all. So this page states how much grapefruit juice changes a PDE5 dose nowhere, because no label states it. What the same labels DO quantify is the effect of the pharmaceutical CYP3A4 inhibitors they name alongside it — ketoconazole, ritonavir, erythromycin — and those come with dose caps. Grapefruit juice comes with neither a figure nor a cap on any of the four, so the only honest instruction this page can give is to raise it with the prescriber rather than to estimate it here.

Figures this tool will not give you

Printed rather than omitted. A number that is missing and a number that was never obtainable look identical on a page.

The figure	Why	Status
How long after a meal it is “safe” to take one	No label models a decaying food effecteach gives one figure for a high-fat meal taken with the dose, and nothing for two or four hours after one	Not stated
An onset of action, for any of the four	No label states one as a timethe lead times in the dosage sections are instructions about when to swallow it, and Tmax is a concentration peak	Not stated
A delay to vardenafil’s peak with food	Its label reports noneit publishes the fall in peak concentration and no Tmax delay; the other three labels’ figures are not transferable	Not computed
How much grapefruit juice raises exposure	Three labels name it, none measures itall three say interactions with it "have not been studied" and that it "would likely" increase exposure	Not stated
A safe number of drinks	The labels disagree and two are silent3 units on one label, 5 on another, and no number at all on the remaining two	Not stated
Whether food changes whether it works	Different question, no trialthe food figures are pharmacokinetic; the efficacy trials for tadalafil and avanafil explicitly did not restrict food or alcohol at all	Not stated

The last row is the most useful one. Section 14 of both the tadalafil and the avanafil labels records that in the pivotal efficacy trials "Food and alcohol intake were not restricted." So the results those drugs are licensed on were produced by men who ate and drank normally. That is not a statement that food and alcohol make no difference — it is a statement that the trials were not designed to find out.

Frequently asked questions

Does food stop Viagra from working?: No label says so, and all four permit food outright — "VIAGRA may be taken with or without food." What the sildenafil label reports is a change in absorption rather than in effect: "When VIAGRA is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%." That moves the median time to peak concentration from 1 hr to 2 hr and lowers the peak by 29%. The label's own patient leaflet puts it as "VIAGRA can be taken with or without food. If you take VIAGRA after a high fat meal (such as a cheeseburger and french fries), VIAGRA may take a little longer to start working" — qualitatively, with no number, which is as far as the label goes and as far as this page goes.
Which ED medication is not affected by food?: Tadalafil, and it is the only one of the four. Its label states it flatly: "The rate and extent of absorption of tadalafil are not influenced by food; thus CIALIS may be taken with or without food." The other three all report something. Sildenafil: a mean delay in Tmax of 60 minutes and a 29% fall in peak concentration with a high-fat meal. Avanafil: a delay of 1.12 to 1.25 hours and a 39% fall at 200 mg, which its label calls "of minimal clinical significance". Vardenafil: a fall in peak concentration of 18% to 50%, with no delay to the peak stated at all.
How long before eating should I take an ED tablet?: No label answers this, and the honest answer is that the question does not have a labelled form. Each of the four gives exactly one food figure — for a high-fat meal taken with the dose — and none of them models what happens if the tablet is swallowed two hours after eating, or four. A curve between "with a meal" and "fasted" would be invented rather than sourced, so this page gives the two states the labels give and nothing between them. What the labels do say, all four of them, is that the tablet may be taken with or without food.
Can I drink alcohol with Viagra or Cialis?: The labels do not agree, which is itself the answer. Tadalafil warns at 5 units or greater — "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., 5 units or greater) in combination with CIALIS can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" — and tells patients "Do not drink too much alcohol when taking CIALIS (for example, 5 glasses of wine or 5 shots of whiskey)." Avanafil warns two units lower and tells patients "Do not drink too much alcohol when taking STENDRA (for example, 3 glasses of wine, or 3 shots of whiskey)." The sildenafil and vardenafil labels name no threshold and say nothing about alcohol to the patient; each reports one interaction study at 0.5 g/kg finding no potentiation of the hypotensive effect. Two of the four labels name a number of units and two name none. A label that says nothing about how much alcohol is too much is not saying that any amount is safe — it is a label whose sponsor ran one interaction study at one alcohol dose and reported the result. The sildenafil label attaches its own caveat to that result: the 100 mg dose, its own maximum, was not the dose tested. These are prescription medicines and the question belongs with the clinician who prescribed one.
How much alcohol is too much with tadalafil?: The CIALIS label names a figure and this page will quote it rather than interpret it: "Therefore, physicians should inform patients that substantial consumption of alcohol (e.g., 5 units or greater) in combination with CIALIS can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache" Its pharmacology section shows the effect is dose-dependent. At 0.7 g/kg — about 6 ounces of 80-proof vodka in an 80 kg man — "In these two studies, more patients had clinically significant decreases in blood pressure on the combination of tadalafil and alcohol as compared to alcohol alone. Some subjects reported postural dizziness, and orthostatic hypotension was observed in some subjects." At 0.6 g/kg, roughly 4 ounces, "When tadalafil 20 mg was administered with a lower dose of alcohol (0.6 g/kg, which is equivalent to approximately 4 ounces of 80-proof vodka, administered in less than 10 minutes), orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated." So the label describes a threshold effect around a specific quantity, not a linear one, and it describes it in healthy volunteers rather than in men on blood pressure medication.
Does grapefruit juice interact with ED medication?: Three of the four labels say it probably does and not one of them says by how much. Tadalafil: "Although specific interactions have not been studied, other CYP3A4 inhibitors, such as erythromycin, itraconazole, and grapefruit juice, would likely increase tadalafil exposure." Vardenafil and avanafil carry the same construction in their own section 7.2. The sildenafil label does not mention grapefruit anywhere. All three of the sentences hedge identically — the interaction "has not been studied" and would "likely" increase exposure — so no percentage, no dose cap and no avoidance instruction exists on any of them to quote. The pharmaceutical CYP3A4 inhibitors named in the same sentences do come with caps; grapefruit does not.
Is a delay in Tmax the same as a delay in when it starts working?: No, and conflating the two is the commonest error on this subject. Tmax is the time at which plasma concentration is highest. A drug is generally doing something well before its peak and continues after it — sildenafil's own label documents an effect out to 4 hours while its median Tmax is 1 hour. No US PDE5 label states an onset of action as a time at all. Three of them give a lead time in the dosage section — approximately 1 hour, approximately 60 minutes, as early as approximately 15 minutes — and those are instructions about when to swallow the tablet, not measurements of when it begins to act. Tadalafil gives no lead time whatsoever, only "prior to anticipated sexual activity".
Did the trials these drugs were approved on control for food and alcohol?: Two of the four labels say in terms that they did not. Section 14 of the tadalafil label, describing both the as-needed and the once-daily programmes: "Food and alcohol intake were not restricted." Section 14 of the avanafil label, describing its four pivotal studies: "Food and alcohol intake was not restricted." That cuts both ways and the page states both. The efficacy those two drugs are licensed on was produced by men eating and drinking normally, which is reassuring. It also means the trials were not designed to measure what food or alcohol did, so they cannot be cited as evidence that neither matters.

Sources

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Next steps

Compare online ED providersAll four are prescription-only, and the food and alcohol questions belong in the consultation. These are the platforms that run one.Work out when to take itOnce you know what dinner does, the other half is the clock — dose time for a planned evening, on the same four labels.