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Key facts at a glance
- Cialis as needed
- Dyspepsia in 4% / 8% / 10% at 5 / 10 / 20 mg vs 1% on placeboCialis (tadalafil) label · DailyMed
- Viagra fixed dose
- Dyspepsia in 3% / 9% / 17% at 25 / 50 / 100 mg vs 2% on placeboViagra (sildenafil) label · DailyMed
- Chest pain during sex
- Stop sexual activity and get medical help right awayCialis (tadalafil) patient information · DailyMed
- Compounded status
- The Mendoxa compounded tablet is not FDA-approvedFDA compounding Q&A
Cialis and Viagra heartburn: label rates by dose
The label term is dyspepsia, not a confirmed diagnosis of acid reflux. The Cialis (tadalafil) label patient leaflet calls it indigestion; the Viagra (sildenafil) label calls it upset stomach. The table keeps dyspepsia and gastroesophageal reflux disease (GERD) separate so you can find the result that matches your question.
| Drug · dose · trial type | Dyspepsia on drug | Dyspepsia on placebo | GERD on drug vs placebo | Source |
|---|---|---|---|---|
| Viagra (sildenafil) 25 mg · fixed-dose trials | 3% | 2% | Not in table | Viagra (sildenafil) label |
| Viagra (sildenafil) 50 mg · fixed-dose trials | 9% | 2% | Not in table | Viagra (sildenafil) label |
| Viagra (sildenafil) 100 mg · fixed-dose trials | 17% | 2% | Not in table | Viagra (sildenafil) label |
| Cialis (tadalafil) 5 mg as needed | 4% | 1% | Not in table | Cialis (tadalafil) label |
| Cialis (tadalafil) 10 mg as needed | 8% | 1% | Not in table | Cialis (tadalafil) label |
| Cialis (tadalafil) 20 mg as needed | 10% | 1% | Not in table | Cialis (tadalafil) label |
| Cialis (tadalafil) 2.5 mg once daily · 12 weeks | 4% | 2% | 2% vs 0% | Cialis (tadalafil) label |
| Cialis (tadalafil) 5 mg once daily · 12 weeks | 5% | 2% | 1% vs 0% | Cialis (tadalafil) label |
| Cialis (tadalafil) 2.5 mg once daily · 24 weeks | 4% | 1% | 3% vs 0% | Cialis (tadalafil) label |
| Cialis (tadalafil) 5 mg once daily · 24 weeks | 1% | 1% | 2% vs 0% | Cialis (tadalafil) label |
Sources: Viagra (sildenafil) label, adverse reaction Tables 1–2 (label revised 12/2017); Cialis (tadalafil) label, adverse reaction Tables 1–4 (label revised 3/2026). “Not in table” means the label table for that trial set has no GERD row. Accessed Oct 31, 2026.
These are separate trials, not a ranking of the two drugs. The Viagra (sildenafil) label cautions against comparing adverse-reaction rates across drugs’ trials. Higher doses had higher dyspepsia rates in its fixed-dose trials and in the as-needed Cialis (tadalafil) label table; that pattern does not consistently hold across the daily-use rows.
For the full side-effect picture, see Viagra side effects and our tadalafil guide; the Cialis (tadalafil) label and Viagra (sildenafil) label remain the primary sources.
Why PDE5 pills can cause heartburn
Relaxation of the lower esophageal sphincter is a plausible explanation, rather than proof of reflux in every user. This ring of muscle helps keep stomach contents out of the esophagus; NIDDK explains the reflux mechanism. Both the Viagra (sildenafil) label and Cialis (tadalafil) label list dyspepsia, but the labels do not establish this as its cause.
In Bortolotti’s 2001 study of 16 healthy adults, sildenafil reduced sphincter pressure compared with placebo. A later study of eight healthy volunteers also found lower pressure, yet no change in measured reflux. These small sildenafil studies support a possible mechanism; they do not measure the chance of heartburn from tadalafil or the compounded tablet. For approved-product adverse reactions, see the Viagra (sildenafil) label and Cialis (tadalafil) label.
How long it lasts, and daily versus as-needed use
The labels give no heartburn-specific duration. The Cialis (tadalafil) label patient leaflet says its most common side effects, including indigestion, “usually go away after a few hours.” The Viagra (sildenafil) label gives no duration for upset stomach.
For a daily schedule, use the daily-use rows above rather than the as-needed percentages: the Cialis (tadalafil) label reports GERD separately in those trials. For timing questions, see daily tadalafil and how long Cialis lasts.
What may help, according to the labels
Ask about the symptom before changing the prescription. The Cialis (tadalafil) label tells patients to contact their provider for a side effect that bothers them or does not go away; the Viagra (sildenafil) label gives the same instruction.
- Food: Sildenafil can be taken with or without food; a high-fat meal can delay its effect (Viagra (sildenafil) label). Tadalafil can be taken with or without food (Cialis (tadalafil) label).
- Antacids with sildenafil: “Single doses of antacid (magnesium hydroxide/aluminum hydroxide) did not affect the bioavailability of VIAGRA” (Viagra (sildenafil) label).
- Antacids with tadalafil: taking that antacid at the same time “reduced the apparent rate of absorption of tadalafil without altering exposure (AUC)” (Cialis (tadalafil) label).
- Other acid reducers: for H2 blockers and PPIs, FDA advises: “ask your doctor or pharmacist before use if you are taking a prescription drug” (FDA: OTC heartburn treatment).
These antacid findings measure drug absorption, not heartburn relief. The Viagra (sildenafil) label and Cialis (tadalafil) label report studies with magnesium hydroxide/aluminum hydroxide; those results do not establish that every antacid has the same effect. Ask your pharmacist about your exact product and ask the prescriber whether your dose or medicine needs review. See sildenafil vs tadalafil for the broader comparison.
When heartburn is not heartburn
Chest pain during sex is a stop sign, not an antacid moment. Both patient leaflets say: “Stop sexual activity and get medical help right away if you get symptoms such as chest pain, dizziness, or nausea during sex” (Viagra (sildenafil) label; Cialis (tadalafil) label).
MedlinePlus warns that with symptoms “such as crushing chest pain, it could be a heart attack. Get help immediately.” NHLBI says to call 9-1-1 “even if you are not sure that you’re having a heart attack.”
Tell responders which ED pill you took and when. Nitrates are contraindicated with sildenafil and tadalafil; after Cialis, the Cialis (tadalafil) label says at least 48 hours should pass before nitrates are considered, and then only under close medical supervision. The Viagra (sildenafil) label also says these drugs should not be used by men for whom sexual activity is inadvisable because of their heart health. Read Viagra and the heart and ED medication and nitrates.
What each path includes
Choose the next step by symptoms. For bothersome or persistent indigestion, contact your prescriber, as directed in the Cialis (tadalafil) label and Viagra (sildenafil) label; use emergency care for the warning signs above.
| Your situation | Starting point | What it includes |
|---|---|---|
| Mild indigestion after some doses | Label patient information and an OTC antacid label check (FDA: OTC heartburn treatment) | The Cialis (tadalafil) label says its common side effects “usually go away after a few hours”; the Viagra (sildenafil) label lists upset stomach |
| Heartburn most days, or reflux at night on a daily pill | A clinician who can assess reflux (NIDDK: GER and GERD) | Whether the timing, dose or a daily regimen is involved; the Cialis (tadalafil) label reports GERD rows only in once-daily trials |
| Changing dose or switching molecule | The prescriber who knows your history; Prescription required | Label dose ranges and your other medicines (Viagra (sildenafil) label; Cialis (tadalafil) label) |
| Asking whether Mendoxa fits | Mendoxa online ED visit with Independent licensed providers | The compounded tablet is not FDA-approved; the standalone label rates do not establish a heartburn rate for this combination |
| Chest pain, pressure or breathlessness | Emergency care: call 9-1-1 (NHLBI) | Do not treat it as heartburn at home; tell responders which ED medicine you took (Cialis (tadalafil) label) |
Sources: Viagra (sildenafil) label; Cialis (tadalafil) label; FDA OTC heartburn treatment; NIDDK; NHLBI; FDA compounding Q&A; Mendoxa care information. Accessed Oct 31, 2026.
Before your visit: note which pill and dose you took, when the heartburn started and how long it lasted, any reflux history, and every medicine and antacid you use. Give the prescriber your full medicine list: the Cialis (tadalafil) label and Viagra (sildenafil) label both include drug-interaction sections, including nitrates.
Could Mendoxa ED care fit you?
Online ED visit · Prescription required · Independent licensed providers · Not available in California
Heartburn and the Mendoxa 3-in-1 tablet
The standalone label rates cannot predict heartburn with the compounded combination. It contains sildenafil and tadalafil, which both list dyspepsia (Viagra (sildenafil) label; Cialis (tadalafil) label), plus apomorphine; the APOKYN (apomorphine) label describes an injectable Parkinson’s medicine and warns about nausea and vomiting.
The compounded tablet is not FDA-approved, so FDA has not reviewed its side-effect profile. Tell the provider about any heartburn or reflux you have had with ED pills; Independent licensed providers decide whether it is suitable. Learn more about the combination ED tablet.
Safety checks before ED medication
- Sildenafil and tadalafil are contraindicated with organic nitrates or riociguat (Viagra (sildenafil) label; Cialis (tadalafil) label).
- An erection lasting more than 4 hours needs immediate medical care (Viagra (sildenafil) label; Cialis (tadalafil) label).
- Stop and seek care for sudden vision loss or sudden decrease or loss of hearing (Viagra (sildenafil) label; Cialis (tadalafil) label).
- Common adverse effects include headache and flushing with sildenafil, and headache, indigestion and back pain with tadalafil (Viagra (sildenafil) label; Cialis (tadalafil) label).
- The APOKYN (apomorphine) label contraindicates use with 5HT3 antagonists such as ondansetron and warns about nausea and fainting.
Do not add another ED medicine to an existing treatment on your own: the Viagra (sildenafil) label and Cialis (tadalafil) label say combinations with other PDE5 inhibitors or ED therapies have not been studied and advise against such use. See ED medication and nitrates for more detail.
Mendoxa ED plans and prices
The Mendoxa ED tablet is a compounded rapid-dissolve tablet with sildenafil (the active ingredient in Viagra), tadalafil (the active ingredient in Cialis) and apomorphine (APOKYN label). It dissolves under the tongue. A licensed clinician decides if it fits you and selects the strength. Compounded medicines are not FDA-approved.
| Tablets per month | 1-month total | Per tablet (1 month) | 3-month total | Per tablet (3 months) |
|---|---|---|---|---|
| 6 tablets / month | $129 | $21.50 | $329 | $18.28 |
| 10 tablets / month | $149 | $14.90 | $379 | $12.63 |
| 20 tablets / month | $179 | $8.95 | $449 | $7.48 |
The 3-month total covers three months at the monthly tablet quantity shown.
If prescribed · Cancel anytime · Available in 49 states (not California). Prices from the Mendoxa intake at try.mendoxa.co/f/ed on Oct 31, 2026. The intake always shows the current price.
FAQ
How can I avoid acid reflux with Cialis?
The Cialis (tadalafil) label says Cialis may be taken without regard to food, and that a magnesium/aluminum hydroxide antacid slowed tadalafil absorption without changing total exposure. If reflux keeps happening, ask your prescriber about dose or timing rather than adjusting it yourself; dyspepsia rates were lower at lower doses on the label.
What are the common side effects of Cialis and Viagra?
Indigestion is among the common reactions listed in the Cialis (tadalafil) label and Viagra (sildenafil) label. Both also list headache and flushing; the tadalafil label also lists back pain. For a fuller discussion beyond heartburn, see Viagra side effects and the tadalafil guide.
When should I take Cialis if I get heartburn?
The Cialis (tadalafil) label permits use with or without food and says to follow the prescribed daily or as-needed schedule. It does not identify a time of day that prevents heartburn. Ask the prescriber before changing your dose or schedule; bring a record of when symptoms follow each dose.
Can I take an antacid with Viagra or Cialis?
The labels studied magnesium hydroxide/aluminum hydroxide: single doses did not affect sildenafil bioavailability (Viagra (sildenafil) label), and simultaneous use slowed tadalafil absorption without altering exposure (Cialis (tadalafil) label). For other products, including H2 blockers and PPIs, FDA advises asking a doctor or pharmacist if you take a prescription drug.
What are the potential drug interactions with tadalafil?
The Cialis (tadalafil) label contraindicates nitrates and riociguat and describes interactions with alpha-blockers, blood-pressure medicines and certain drugs that affect tadalafil exposure. Give the provider your full medicine list, including OTC acid reducers; an antacid study does not rule out other interactions.
How do I know if it is heartburn or a heart problem?
You cannot be sure at home. Both the Viagra (sildenafil) label and Cialis (tadalafil) label say to stop sexual activity and get medical help right away for chest pain, dizziness or nausea during sex; NHLBI says to call 9-1-1 even if you are not sure it is a heart attack.
Ready to see if the Mendoxa ED tablet fits you?
From $129/month if prescribed · Cancel anytime · Available in 49 states (not California)
How we wrote this
Written by the Mendoxa editorial team · Sources: DailyMed/FDA. Medical facts on this page come from the FDA-approved labels on DailyMed and Drugs@FDA; each drug name links to its label. Label tables and saved official sources were checked on Oct 31, 2026. Trial rates describe separately approved products and cannot predict your symptoms or the safety or effectiveness of a compounded combination. Mechanism studies describe esophageal pressure; they do not prove that every user develops reflux.
Updated Oct 31, 2026. This page is general information, not medical advice. A licensed clinician decides what fits you.
References
- DailyMed: VIAGRA (sildenafil citrate) tablet, film coated, label revised 12/2017. Accessed Oct 31, 2026.
- DailyMed: CIALIS (tadalafil) tablet, film coated, label revised 3/2026. Accessed Oct 31, 2026.
- DailyMed: APOKYN (apomorphine hydrochloride) injection, label revised 6/2022. Accessed Oct 31, 2026.
- FDA (Drugs@FDA): VIAGRA (sildenafil) prescribing information, NDA 020895. Accessed Oct 31, 2026.
- FDA (Drugs@FDA): CIALIS (tadalafil) prescribing information, NDA 021368. Accessed Oct 31, 2026.
- FDA: Compounding and the FDA, questions and answers. Accessed Oct 31, 2026.
- Bortolotti M, et al. Effects of sildenafil on esophageal motility of normal subjects. Dig Dis Sci. 2001;46(11):2301-6. PMID 11713926. Accessed Oct 31, 2026.
- Kim HS, Conklin JL, Park H. The effect of sildenafil on segmental oesophageal motility and gastro-oesophageal reflux. Aliment Pharmacol Ther. 2006;24(7):1029-36. PMID 16984496. Accessed Oct 31, 2026.
- FDA: Over-the-Counter (OTC) Heartburn Treatment. Accessed Oct 31, 2026.
- NIDDK: Symptoms and causes of GER and GERD. Accessed Oct 31, 2026.
- MedlinePlus: Heartburn. Accessed Oct 31, 2026.
- NHLBI: Heart attack symptoms. Accessed Oct 31, 2026.
- Mendoxa ED care (product, format, max 1 dose per 24 hours). Accessed Oct 31, 2026.
- Mendoxa ED intake: plan prices (term_options). Accessed Oct 31, 2026.
About Mendoxa
Mendoxa (mendoxa.co) is a US telehealth brand. Independent licensed providers (licensed clinicians in the LocumTele network) review each online visit, and prescriptions are filled by Rush Pharmacy, a licensed US pharmacy. Available in 49 states (not California).
- Prescription required. A licensed clinician reviews every visit and can say no. A prescription is not automatic.
- A compounded medicine is not an FDA-approved finished product (FDA compounding Q&A).
- Plans: 1 month or 3 months, from $129. If prescribed · Cancel anytime · Available in 49 states (not California).
Compounded medication prescribed only if a licensed U.S. clinician decides it is appropriate. Not FDA-approved as a finished product. Not available in California. This site is not for emergencies. Call 911 if you need urgent care.