Can You Take Viagra or Cialis With Ozempic / Zepbound?

The short answer is yes — sildenafil (Viagra), tadalafil (Cialis), vardenafil, and avanafil are not flagged for any clinically significant pharmacokinetic interaction with semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound) in the FDA labels or the published systematic review of GLP-1 oral drug interactions (Calvarysky 2024^[1]). The only practical consideration is timing: GLP-1s slow gastric emptying, which can delay the onset of on-demand sildenafil or vardenafil by 20–30 minutes. Tadalafil daily and avanafil are largely unaffected. This article walks through the FDA labels, the published interaction evidence, and a clinician-style timing protocol for each of the four PDE5 inhibitors.

The honest summary

• No PK interaction is documented. The Calvarysky 2024 systematic review^[1] (Drug Safety) cataloged every published GLP-1 oral-drug PK interaction and PDE5 inhibitors are not on the list. The Ozempic ^[6], Wegovy^[7], Mounjaro^[9], and Zepbound^[8] FDA labels make no specific mention of sildenafil, tadalafil, vardenafil, or avanafil in their Drug Interactions section.
• Timing matters for sildenafil on tirzepatide. The Zepbound and Mounjaro labels^[8][9] report a 55–66% reduction in Cmax and 20–23% reduction in AUC for an oral contraceptive co-administered with a single 5 mg tirzepatide dose. The mechanism is delayed gastric emptying; the same delay can push sildenafil's onset from 30–60 minutes out to 60–90 minutes. Take sildenafil 60–90 minutes before activity if you are on tirzepatide titration.
• Tadalafil is the cleanest stack. Tadalafil has a 17.5-hour half-life and is typically dosed daily (2.5 or 5 mg, Porst 2006^[3]); peak concentration timing is not therapeutically relevant because steady-state coverage is continuous. No timing adjustment is needed on any GLP-1.
• The nitrate contraindication is unchanged. PDE5 inhibitors plus nitrates remain an absolute contraindication regardless of GLP-1 use. GLP-1 therapy does not modify the nitrate interaction in either direction.

What the FDA labels actually say

We checked all four FDA labels via DailyMed (the NIH-hosted canonical mirror) on 2026-05-28.

Ozempic and Wegovy (semaglutide, SetIDs adec4fd2^[6] and ee06186f^[7]). Section 7 Drug Interactions states that semaglutide delays gastric emptying and has the potential to impact the absorption of concomitantly administered oral medications, but that clinical pharmacology studies “did not show any clinically relevant effect on the rate or extent of absorption” of the oral drugs tested (acetaminophen, oral contraceptive, atorvastatin, digoxin, warfarin, metformin). Sildenafil, tadalafil, vardenafil, and avanafil are not specifically listed but fall into the “no clinically relevant effect” class.

Zepbound and Mounjaro (tirzepatide, SetIDs 487cd7e7^[8] and d2d7da5d^[9]). Section 7 is more cautious. Tirzepatide reduced the Cmax of a single 0.035 mg ethinyl estradiol / 0.25 mg norgestimate oral contraceptive dose by 55% and the AUC by 20% after a single 5 mg tirzepatide dose; for norelgestromin (the active metabolite) the reduction was 41% Cmax and 23% AUC. The label therefore recommends a non-oral or barrier contraceptive method or addition of a barrier method for 4 weeks after initiation and after each dose escalation. The label does not extend this caution to short-acting on-demand oral drugs outside the contraceptive class.

The clinical translation: tirzepatide can blunt and delay peak absorption of orally administered drugs taken alongside a tirzepatide injection or during the days following a dose escalation. For sildenafil this means the onset window (normally 30–60 minutes after a fasted oral dose) can extend to 60–90 minutes. The total exposure (AUC) is less affected, so peak efficacy is preserved — just delayed.

The Calvarysky 2024 systematic review

Calvarysky and colleagues^[1] published the most comprehensive systematic review to date of GLP-1 RA oral drug interactions in Drug Safety (2024). They searched PubMed, Embase, and Web of Science for every published clinical pharmacology study reporting a co-administration PK endpoint between a GLP-1 RA and an oral medication. The review covered exenatide, liraglutide, lixisenatide, semaglutide (oral and subcutaneous), and tirzepatide; the oral drugs covered included acetaminophen, atorvastatin, digoxin, warfarin, metformin, oral contraceptives, statins, antibiotics, and several others.

PDE5 inhibitors do not appear in the Calvarysky systematic review's clinically significant interaction list. The absence is informative because the review's search strategy would have captured any published sildenafil, tadalafil, vardenafil, or avanafil co-administration study; no such study has been published because the manufacturer sponsors did not flag a signal that would have justified one.

The PDE5 pharmacokinetics that matter

Each of the four PDE5 inhibitors has a distinct PK profile, and only two of them are theoretically sensitive to the gastric-emptying delay imposed by a GLP-1.

Sildenafil (Viagra): Cmax at approximately 1 hour post-dose under fasting conditions; terminal half-life ~4 hours; hepatic metabolism via CYP3A4. The pivotal Goldstein 1998 NEJM trial^[2] recommended dosing 1 hour before activity. On a GLP-1, the practical window shifts to 60–90 minutes — the total dose absorbed is preserved, the time to peak is delayed.

Tadalafil (Cialis): Cmax at 2 hours; terminal half-life ~17.5 hours — the longest of the class. Porst 2006^[3] established once-daily 2.5 and 5 mg dosing for both ED and BPH; at steady state the time-to-peak is not therapeutically relevant. No timing adjustment needed on any GLP-1. This is the cleanest stack and our default suggestion for GLP-1 patients with ED who want a daily option.

Vardenafil (Levitra, Staxyn): Cmax at ~45–60 minutes; half-life ~4–5 hours; CYP3A4 metabolism. Same timing consideration as sildenafil — push the dose to 60–90 minutes before activity on a tirzepatide ladder.

Avanafil (Stendra): Cmax at ~30–45 minutes; half-life ~5 hours. The fastest onset of the class. On a GLP-1 the practical onset shifts to 45–60 minutes, still the quickest of the four.

Magnitude: IIEF-EF improvement at week 12

Cardiovascular safety: the SELECT context

The patient population most likely to need both a GLP-1 and a PDE5 inhibitor — men with obesity, type 2 diabetes, or established cardiovascular disease — is the same population studied in the SELECT trial. SELECT (Lincoff 2023 NEJM^[5]) randomized 17,604 adults with established CVD and overweight/obesity (without diabetes) to semaglutide 2.4 mg weekly or placebo. Over a mean 39.8 months of follow-up, semaglutide reduced major adverse cardiovascular events (MACE) by 20% (HR 0.80, 95% CI 0.72–0.90, p < 0.001). The CV-benefit signal means that men with established CVD who are weighing a GLP-1 plus a PDE5 inhibitor are stacking two CV-conditional therapies in a population where the CV math favors both.

PDE5 inhibitors are themselves not contraindicated in stable coronary disease — the absolute contraindication is nitrates (organic nitrates including nitroglycerin, isosorbide mononitrate, and isosorbide dinitrate; also recreational amyl nitrite). That contraindication is unchanged by GLP-1 therapy. Any patient on a nitrate cannot use a PDE5 inhibitor regardless of GLP-1 status.

The practical protocol

1. Sildenafil on-demand: 50–100 mg taken 60–90 minutes before anticipated activity if on tirzepatide (Zepbound or Mounjaro) at 5 mg or higher; 60 minutes is fine on semaglutide (Ozempic or Wegovy) maintenance.
2. Tadalafil daily: 2.5 or 5 mg once daily at the same time every day. Effective for both ED and BPH/LUTS (Porst 2006^[3]). No GLP-1-related timing adjustment. This is the default we recommend for patients who want a low-friction daily option.
3. Tadalafil on-demand: 10 or 20 mg taken 90–120 minutes before activity on any GLP-1. The long half-life makes timing forgiveness inherent.
4. Vardenafil on-demand: 10 or 20 mg taken 60–90 minutes before activity on tirzepatide; 60 minutes on semaglutide.
5. Avanafil on-demand: 100 or 200 mg taken 45–60 minutes before activity on any GLP-1. The shortest onset of the four.
6. Verify no nitrate use. Any nitrate is an absolute contraindication. Confirm with the prescribing clinician at every visit.
7. Skip the alcohol-heavy night. Alcohol plus PDE5 inhibitor plus GLP-1-induced delayed emptying increases nausea and orthostatic risk without adding efficacy.

When weight loss alone is enough

For obesity-linked ED with no underlying vascular or neurogenic component, GLP-1-mediated weight loss alone often reverses the ED within 6–12 months — see our companion article on the Esposito 2004, Pizzol 2020, and Corona 2013 evidence. For men with concomitant hypogonadism, the Endocrine Society testosterone therapy guideline (Bhasin 2018^[4]) recommends confirming symptomatic biochemical hypogonadism on two morning total testosterone measurements before initiating TRT; weight loss alone restores free testosterone in many cases of obesity-induced hypogonadotropic hypogonadism, so the sequencing question (lose weight first, then re-test) is meaningful.

Related research and tools

• Does GLP-1 weight loss reverse ED? — the Esposito 2004 / Pizzol 2020 / Corona 2013 mechanism evidence
• Best ED telehealth providers — sildenafil and tadalafil routes that integrate with GLP-1 prescribing
• TRT and GLP-1 stacking — when low testosterone is part of the ED picture