Alcohol and Tadalafil: What the Cialis FDA Label Says

Almost every article about alcohol and tadalafil paraphrases the same source: the FDA-approved prescribing information.

Very few quote it.

That is a shame, because the label is more specific than the summaries built on top of it. It names a figure. It describes the studies that produced that figure, including how much alcohol participants were given, how quickly they drank it, and what happened to their blood pressure. And it says something about the two drugs' behaviour together that most coverage leaves out entirely.

Here is what the label says, in its own words.

The Short Answer

The CIALIS label describes alcohol and tadalafil as both being mild vasodilators, and states that combining mild vasodilators may increase the blood-pressure-lowering effect of each.

It gives “5 units or greater” as an example of substantial alcohol consumption associated with an increased potential for orthostatic signs and symptoms — including increased heart rate, decreased standing blood pressure, dizziness and headache.

That figure is an example the label uses, not a boundary it establishes. Nothing in the underlying studies shows that four units is safe and five is not.

The label also reports that tadalafil and alcohol do not affect each other's plasma concentrations. The interaction it describes is about combined blood-pressure effects, not about one drug changing the levels of the other.

What the Label Says, Word for Word

Alcohol appears in five separate places in the current CIALIS prescribing information: the Highlights summary, Warnings and Precautions, Drug Interactions, Clinical Pharmacology, and Patient Counseling Information.

Highlights of Prescribing Information

“Use of CIALIS with alpha-blockers, antihypertensives or substantial amounts of alcohol (≥5 units) may lead to hypotension.”

Section 5.9, Warnings and Precautions — Alcohol

“Patients should be made aware that both alcohol and CIALIS, a PDE5 inhibitor, act as mild vasodilators.”

“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.”

Note the construction: e.g. — for example. The label is illustrating what it means by substantial, not drawing a line.

Section 7.1, Drug Interactions

“Both alcohol and tadalafil, a PDE5 inhibitor, act as mild vasodilators. When mild vasodilators are taken in combination, blood-pressure-lowering effects of each individual compound may be increased.”

And a sentence that rarely appears in secondary coverage:

“Tadalafil did not affect alcohol plasma concentrations and alcohol did not affect tadalafil plasma concentrations.”

Section 17.9, Patient Counseling Information — Alcohol

The same example is repeated in the section describing what patients should be told: substantial consumption of alcohol, given as 5 units or greater, in combination with CIALIS can increase the potential for orthostatic signs and symptoms.

Read the current CIALIS prescribing information on DailyMed.

The Studies Behind That Figure

Section 12.2 of the label describes what was actually tested, and the detail is worth having in full.

The label states that “the interaction of tadalafil with alcohol was evaluated in 3 clinical pharmacology studies.”

In two of them, alcohol was given at a dose of 0.7 g/kg — which the label describes as “equivalent to approximately 6 ounces of 80-proof vodka in an 80-kg male.” Tadalafil was given at 10 mg in one study and 20 mg in the other. The label adds two details that matter: “all patients imbibed the entire alcohol dose within 10 minutes of starting,” and in one of the two studies, blood alcohol levels of 0.08% were confirmed.

The findings, quoted in full: “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.”

A lower alcohol dose was also tested. When tadalafil 20 mg was given with alcohol at 0.6 g/kg — “approximately 4 ounces of 80-proof vodka, administered in less than 10 minutes” — the label reports that “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 is not describing a uniform effect. It reports different findings at two alcohol doses roughly 17% apart, both consumed rapidly, under study conditions — which is a different thing from establishing where the safe amount ends.

What “5 Units” Does and Does Not Mean

The figure comes from the label, and it is the label's own illustration of “substantial” consumption. It is worth being precise about what that is, because it is frequently reported as a limit.

It is an example used in prescribing information to describe where the potential for orthostatic effects increases. It is not a finding that any amount below it is safe for a particular person, and it is not a recommendation about how much anyone should drink. The studies behind it compared two specific doses in healthy volunteers; they were not designed to locate a cutoff, and they did not find one.

A unit is also not a universal measure. Standard drink definitions differ between countries, and the volumes described in the label's own studies — 6 ounces and 4 ounces of 80-proof spirits, consumed within ten minutes — are more specific than the word “units” conveys on its own.

Individual factors the studies were not designed to capture include body weight, what else a person takes, blood pressure, cardiovascular health, whether food was eaten, and how quickly the alcohol was consumed.

Why Tadalafil's Label Reads Differently From Sildenafil's

People often assume the PDE5 inhibitors carry identical alcohol warnings. The labels do not read the same way, and the difference is structural as well as verbal.

In the CIALIS label, alcohol appears in the Highlights summary, in Warnings and Precautions, and in Patient Counseling Information. In the VIAGRA label, alcohol appears only under Drug Interactions and in the pharmacodynamics section — there is no alcohol subsection in its Warnings and Precautions.

What VIAGRA's label reports is a single drug interaction study: sildenafil 50 mg given with alcohol at 0.5 g/kg, producing mean maximum blood alcohol levels of 0.08%. Its finding is that sildenafil “did not potentiate the hypotensive effect of alcohol in healthy volunteers.”

The label gives the numbers. The maximum observed decrease in systolic blood pressure was −18.5 mmHg with sildenafil plus alcohol, versus −17.4 mmHg with alcohol alone. For diastolic pressure the figures were −17.2 mmHg versus −11.1 mmHg. It adds: “There were no reports of postural dizziness or orthostatic hypotension.” Read the current VIAGRA prescribing information on DailyMed.

An important caveat about comparing them. These were not head-to-head studies. The alcohol doses differ — 0.5 g/kg in the sildenafil study, 0.6 and 0.7 g/kg in the tadalafil studies. The drug doses differ, and the VIAGRA label notes that “the maximum recommended dose of 100 mg sildenafil was not evaluated in this study.” The designs and populations differ. A difference in how two labels describe alcohol does not establish that one medication is safer with alcohol than the other; it reflects what each manufacturer studied and what each study found.

It is worth noting that at a comparable measured blood alcohol level of 0.08%, the tadalafil studies reported orthostatic hypotension in some subjects and the sildenafil study reported none. That is a real difference in reported outcomes — but across separate studies with different drug doses, alcohol doses and designs, it is not evidence of a difference between the drugs.

Timing, and What the Label Does Not Say About It

Where the labels are directly comparable is pharmacokinetics.

The CIALIS label states that “the mean oral clearance for tadalafil is 2.5 L/hr and the mean terminal half-life is 17.5 hours in healthy subjects,” and that CIALIS used as needed was shown to improve erectile function compared to placebo up to 36 hours following dosing.

That long window is the feature tadalafil is known for.

What follows is a pharmacokinetic inference, not label guidance. A longer half-life means the period during which tadalafil and alcohol may both be present in the body is wider than for a shorter-acting medication. Someone who takes tadalafil on a Friday afternoon and drinks on Saturday evening is therefore in a different situation from someone taking a shorter-acting medication an hour before activity — not because the interaction is stronger, but because the overlap can last longer.

The label does not study that scenario, does not comment on it, and gives no waiting period between a tadalafil dose and alcohol. The inference is reasonable; it is not an instruction, and it is not a substitute for asking the person who prescribed the medication. Related reading: Daily Tadalafil vs. As Needed: 5 mg vs 10–20 mg Explained.

Compounded Tadalafil Is Not the Labelled Product

Everything above describes CIALIS, the FDA-approved tadalafil product, and the studies submitted in support of it.

Tadalafil's basic pharmacology does not change when it is compounded. It is the same active ingredient, acting on the same enzyme, and the mechanism described above — mild vasodilation, additive with alcohol's — remains relevant.

What does not automatically transfer are the specific findings. Absorption, peak concentration, half-life, and the interaction data generated for a 10 mg or 20 mg CIALIS tablet were produced with that product, at those doses, by that route. A compounded preparation — a different formulation, a different dose, a sublingual film rather than a swallowed tablet, or a combination containing other active ingredients — has not been studied that way, and compounded medications are not reviewed by the FDA before marketing for safety, effectiveness or quality.

So the label remains the best available guide to how tadalafil behaves, and it remains an imperfect guide to how any particular compounded preparation behaves. Anyone prescribed one should raise questions about alcohol with the clinician who prescribed it, rather than reasoning from the CIALIS label alone.

What This Does and Does Not Answer

The label describes what was studied and what the manufacturer is required to communicate. Read carefully, it is clear about its own limits.

It does not establish a universally safe number of drinks. It does not give a waiting period between taking tadalafil and drinking, in either direction. And it does not show that amounts below 5 units are safe for everyone — the studies compared two doses in healthy volunteers and were never designed to locate a threshold.

Blood pressure, cardiovascular history, other medications — the label lists interactions considerably more serious than alcohol, including contraindications — age, body weight and other health conditions all bear on those questions, and none of them are addressed by an example in prescribing information.

That assessment belongs to a licensed provider who can see the whole picture. Related reading: Does Alcohol Cause Erectile Dysfunction? What the Research Actually Shows and Why Viagra or Cialis Sometimes Doesn't Work.

Frequently Asked Questions

What does the Cialis label say about alcohol?

It states that both alcohol and CIALIS act as mild vasodilators, and that when mild vasodilators are combined the blood-pressure-lowering effect of each may be increased. It gives “5 units or greater” as an example of substantial alcohol consumption that increases the potential for orthostatic signs and symptoms, including increased heart rate, decreased standing blood pressure, dizziness and headache.

Is 5 units a safe limit for drinking on Cialis?

No. It is an example the label uses to illustrate what it means by substantial consumption — signalled by “e.g.” in the label's own wording. It is not a finding that less is safe for any particular person, and not a recommendation about drinking. Standard drink definitions also vary between countries.

How much alcohol was used in the label's studies?

The label reports three clinical pharmacology studies. Two used alcohol at 0.7 g/kg, described as approximately 6 ounces of 80-proof vodka in an 80-kg male, with tadalafil at 10 mg and 20 mg; all participants drank the full dose within 10 minutes, and blood alcohol of 0.08% was confirmed in one. A separate test used alcohol at 0.6 g/kg, approximately 4 ounces of 80-proof vodka in under 10 minutes, with tadalafil 20 mg.

What happened in those studies?

At 0.7 g/kg, the label reports that more patients had clinically significant decreases in blood pressure on the combination than on alcohol alone, that some subjects reported postural dizziness, and that orthostatic hypotension was observed in some subjects. At 0.6 g/kg with tadalafil 20 mg, orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated.

How long after taking Cialis can you drink alcohol?

The label gives no waiting period, in either direction. It reports a mean terminal half-life of 17.5 hours in healthy subjects and efficacy up to 36 hours after dosing, but it does not translate those figures into timing guidance about alcohol. That question is one for the prescribing clinician.

Does alcohol make tadalafil less effective?

The label does not report a change in drug levels. It states that tadalafil did not affect alcohol plasma concentrations and alcohol did not affect tadalafil plasma concentrations. The interaction described concerns combined effects on blood pressure, not effectiveness.

Do sildenafil and tadalafil have the same alcohol warning?

No. The CIALIS label carries alcohol in its Highlights, its Warnings and Precautions and its Patient Counseling Information; the VIAGRA label addresses it only under Drug Interactions and pharmacodynamics. VIAGRA's label reports that sildenafil 50 mg did not potentiate the hypotensive effect of alcohol at 0.5 g/kg, and notes that the maximum 100 mg dose was not evaluated in that study. The studies were not head-to-head and used different alcohol and drug doses, so the difference in labelling does not establish that one interacts more strongly than the other.

How long does tadalafil stay in the body?

The CIALIS label gives a mean terminal half-life of 17.5 hours in healthy subjects, and states that as-needed CIALIS improved erectile function compared to placebo up to 36 hours after dosing.

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References

1. CIALIS® (tadalafil) tablets — U.S. Prescribing Information. DailyMed, U.S. National Library of Medicine. Highlights, and sections 2.1, 5.9, 7.1, 12.2, 12.3 and 17.9.
2. VIAGRA® (sildenafil citrate) tablets — U.S. Prescribing Information. DailyMed, U.S. National Library of Medicine. Sections 7.5 and 12.2.
3. Compounding and the FDA: Questions and Answers. U.S. Food and Drug Administration.

This article is provided for general educational purposes only and is not a substitute for individualized medical advice, diagnosis or treatment. It reports the contents of FDA-approved prescribing information and does not recommend any level of alcohol consumption. Prescription medications should be used only as prescribed, and questions about alcohol, interactions and dosing should be discussed with a qualified healthcare professional. AmalfiDuo Journal articles are written by AmalfiDuo Editorial and are not medically reviewed — see our Editorial Policy.

CIALIS® and VIAGRA® are trademarks of their respective owners. AmalfiDuo is not affiliated with or endorsed by the owners or manufacturers of these brands.