Quattro Side Effects and Safety: What to Know Before a Consult
Quattro's side effects are, in practice, the side effects of its four ingredients. Here is what the FDA labels and published trials say about each, and which medications rule a combination out entirely.
The short version
- Quattro combines sildenafil, tadalafil, vardenafil and apomorphine.1 Its side-effect profile comes from those four drugs.
- Headache and flushing are the most common side effects of PDE5 inhibitors.2,3
- Nausea is the most common side effect of sublingual apomorphine.4
- Nitrates and riociguat are an absolute no with any PDE5 inhibitor.2
- The four-drug combination has not been studied as a whole, so a clinician's review matters.2,5
No clinical trial has tested Quattro's exact formula, so there is no Quattro-specific list of side effects. What does exist is a large body of evidence on each of its ingredients, including the FDA prescribing information for sildenafil, tadalafil and vardenafil and a controlled trial of sublingual apomorphine.2,3,6,4 This guide pulls that evidence together.
Common side effects, by ingredient
| Ingredient | Most commonly reported |
|---|---|
| Sildenafil | Headache, flushing, indigestion, nasal congestion, changes in color vision2,7 |
| Tadalafil | Headache, indigestion, back pain, muscle aches, flushing, nasal congestion3,8 |
| Vardenafil | Headache, flushing, nasal congestion, indigestion6 |
| Apomorphine (sublingual) | Nausea, more frequent at higher doses4 |
The three PDE5 inhibitors share a mechanism, so their common side effects overlap heavily. Tadalafil is the one most associated with back pain and muscle aches, which can appear 12 to 24 hours after a dose.3
Medications that rule it out
- Nitrates in any form, including nitroglycerin tablets, sprays and patches, and recreational "poppers." Combined with a PDE5 inhibitor they can cause a dangerous drop in blood pressure.2
- Guanylate cyclase stimulators such as riociguat, used for pulmonary hypertension.2
Medications that need a careful review
- Alpha-blockers (often prescribed for blood pressure or an enlarged prostate) also lower blood pressure.2
- Strong CYP3A4 inhibitors, including some antifungals, HIV medications and antibiotics, raise PDE5 inhibitor levels in the blood.2,3
- Other ED treatments. The sildenafil label says combining it with other ED treatments has not been studied and is not recommended.2 A compounded combination is a clinician's decision to make for an individual patient.
- Heavy alcohol use together with a PDE5 inhibitor can lower blood pressure and cause dizziness or fainting.3
Rare but serious
The FDA labels for PDE5 inhibitors describe a small number of serious events that need immediate care: an erection lasting more than four hours (priapism), sudden loss of vision in one or both eyes, and sudden decrease or loss of hearing.2,3 These are uncommon, but they are the reason every PDE5 prescription comes with the same warning.
Why a combination needs more care, not less
Quattro's ingredients are each familiar to prescribers, but taking four drugs at once is different from taking one. Because the combination has not been studied, and because compounded drugs are not FDA-approved,2,5 the honest framing is that a clinician is weighing known single-drug risks against an individual's health history. That is why the intake asks about heart health, blood pressure and every current medication, and why the clinician can decline to prescribe.
Questions worth asking the clinician
- Given my medications, is any ingredient in this combination a problem for me?
- What dose of each ingredient are you prescribing, and why?
- What should I do if I get nausea, a headache or dizziness after a dose?
- Would a single medication be a better place to start for me?
Have questions about safety?
Every Quattro prescription starts with a health questionnaire reviewed by a licensed clinician, who can ask follow-up questions or decline to prescribe. You are not charged unless a clinician approves.
See if Quattro is right for you →Sponsored. Quattro is compounded by a state-licensed 503A pharmacy for an individual patient. Compounded drugs are not FDA-approved and have not been reviewed by the FDA for safety or effectiveness. Prescription required; subject to clinician approval.
Frequently asked questions
What are the side effects of Quattro?
Quattro's side effects come from its four ingredients. Headache and flushing are most common with sildenafil, tadalafil and vardenafil, and nausea is most common with sublingual apomorphine.
Can I take Quattro with nitroglycerin?
No. Nitrates in any form, including nitroglycerin, must not be taken with any PDE5 inhibitor, and Quattro contains three of them.
Can I drink alcohol with Quattro?
Heavy drinking with a PDE5 inhibitor can lower blood pressure and cause dizziness or fainting. Ask the prescribing clinician what is safe for you.
When should I get emergency care?
Get emergency care for an erection lasting more than four hours, sudden vision loss, sudden hearing loss, or chest pain.
Keep reading
Sources
- Vea Health. Quattro. Accessed October 9, 2026.
- Pfizer. VIAGRA (sildenafil citrate) prescribing information. DailyMed, U.S. National Library of Medicine.
- Eli Lilly. CIALIS (tadalafil) prescribing information. DailyMed, U.S. National Library of Medicine.
- Dula E, et al. Double-blind, crossover comparison of 3 mg apomorphine SL with placebo and with 4 mg apomorphine SL in male erectile dysfunction. Eur Urol. 2001. PubMed 11464037.
- U.S. Food and Drug Administration. Compounding and the FDA: Questions and Answers.
- Vardenafil hydrochloride prescribing information. DailyMed, U.S. National Library of Medicine.
- Sildenafil. MedlinePlus Drug Information, U.S. National Library of Medicine.
- Tadalafil. MedlinePlus Drug Information, U.S. National Library of Medicine.
Advertising disclosure. Men's Health Insider is published in partnership with Vea Health, which makes Quattro, the product covered on this page. We may earn compensation when readers buy through links here. Nothing on this site is medical advice; a licensed clinician should decide what is right for you.