For ordinary, short-lived indigestion or an upset stomach, OTC products are a reasonable first step when matched to the actual symptom (acid vs. gas vs. diarrhea) — a point the draft makes correctly. The key caveat: OTC medicines relieve symptoms and do not fix an underlying cause, and self-treatment is time-limited (about 2 weeks for the acid products, 48 hours for diarrhea). See a clinician for symptoms that are severe, persistent/recurrent, or carry any red flag below — and treat chest pain as a possible cardiac emergency, not heartburn.
Neutralizes acid already in the stomach for fast but short-lived relief of occasional heartburn and acid indigestion.
MedlinePlus: used "as an antacid to relieve heartburn, acid indigestion, and upset stomach." Verified verbatim on MedlinePlus a601032.
Caution: Do not use as an antacid for more than 2 weeks unless a doctor tells you to. Can block absorption of other drugs — separate by 1-2 hours. Caution with kidney disease. Relieves symptoms; does not treat the cause.
Reduces stomach acid production; slower onset than an antacid but longer-lasting, and can be taken 15-60 minutes before a trigger meal to prevent heartburn.
MedlinePlus: "Famotidine is in a class of medications called H2 blockers. It works by decreasing the amount of acid made in the stomach." Pre-meal timing and limits verified verbatim on a687011.
Caution: OTC limit: no more than two tablets in 24 hours and no longer than 2 weeks unless a doctor directs. If heartburn/acid indigestion lasts longer than 2 weeks, stop and call a doctor. Daily need for weeks warrants evaluation.
Acts on gas bubbles in the gut to ease pressure, fullness, and bloating; not absorbed systemically to any meaningful degree.
MedlinePlus: "Simethicone is used to treat the symptoms of gas such as uncomfortable or painful pressure, fullness, and bloating" and "usually has no side effects" when taken as directed. Verified on a682683.
Caution: Only helps gas — useless for acid symptoms or nausea. Very safe, but efficacy is limited to the specific complaint of gas/bloating; pick the matching product for other symptoms.
Broad 'upset stomach' relief including indigestion, nausea, and mild diarrhea in adults; also reduces travelers' diarrhea incidence by ~50%.
MedlinePlus: treats "diarrhea, heartburn, and upset stomach in adults and children 12 years of age and older." CDC Yellow Book: reduces TD incidence "by approximately 50%." Both verified verbatim.
Caution: It is a salicylate (aspirin-related): avoid if allergic to aspirin/salicylates; do NOT give to children/teens recovering from chickenpox or flu (Reye syndrome risk — label is age 12+). CDC: not recommended for children under 3 or in pregnancy. Harmless black stool/tongue darkening expected. Stop and call a doctor if diarrhea lasts over 48 hours or stools are bloody/black.
Replaces fluids and salts lost to vomiting or diarrhea — the priority over any stomach medicine when losses are significant.
CDC Yellow Book: "Fluids and electrolytes are lost during [diarrhea], and replenishment is important, especially in young children, older adults, and adults with chronic medical illness." Verified verbatim.
Caution: Do not use salt tablets (MedlinePlus: "can cause serious complications"). Antimotility (anti-diarrhea) drugs alone are NOT recommended with bloody diarrhea or diarrhea plus fever — those need a clinician. Watch infants, older adults, and chronically ill people closely for dehydration.
For mild, short-lived indigestion or upset stomach, OTC works well when matched to the symptom: calcium carbonate for fast occasional acid relief, famotidine for longer-lasting or preventable heartburn, simethicone for gas/bloating, bismuth subsalicylate for a broad upset stomach or mild diarrhea only if aspirin-type drugs are safe for you, and oral rehydration first whenever vomiting or diarrhea is significant. Respect the label time limits (about 2 weeks for acid products; stop diarrhea self-treatment at 48 hours) and never use OTC to mask red-flag symptoms. Chest pain, GI bleeding (vomiting blood or black/tarry stools), dehydration, high fever, trouble swallowing, unexplained weight loss, or symptoms that persist or recur mean see a clinician — not another dose.
General information, not medical advice, and not a substitute for your clinician or pharmacist. Follow the label on any OTC product, mind interactions with your other medicines, and seek care for any red-flag symptom.