Heartburn, acid reflux, a sour taste in your mouth, or a queasy “mukamuka” stomach can make a trip in Japan uncomfortable fast. The hard part is that many Japanese stomach medicines look similar on the shelf.
This quick guide focuses on one practical question: which OTC ingredient names are commonly used for acid-related symptoms in Japan, and when should you stop self-treating and get medical advice?
Quick Answer: What to Look For First
If your symptoms feel like burning, acid coming up, or a sour/bitter taste after meals or when lying down, Japanese OTC products may include these acid-related ingredients:
| Label clue | Category | Plain meaning |
| Synthetic hydrotalcite, magnesium aluminometasilicate, dried aluminum hydroxide gel, magnesium oxide, magnesium hydroxide, calcium carbonate, sodium bicarbonate | Antacid | Helps neutralize stomach acid already present |
| Famotidine / ファモチジン | H2 blocker | Reduces stomach acid secretion |
| Lansoprazole, omeprazole, rabeprazole sodium | PPI | Reduces stomach acid secretion by a different mechanism |
These are ingredient clues, not product recommendations. Japanese stomach medicines often combine several ingredients, so the full label still matters.
Useful Japanese label words include 胸やけ (heartburn), 胃酸 (stomach acid), 胃部不快感 (stomach discomfort), and むかつき (queasiness). If diarrhea, constipation, cramping, or vomiting is your main problem, start with the broader guide: Stomach and Digestive Problems in Japan: OTC Medicine Ingredients and Safety Checks.
If your main word is mukamuka / むかつき, tell pharmacy staff what you actually feel. Mukamuka can mean queasiness or stomach discomfort, not always acid reflux. If you also have burning, acid coming up, or a sour taste, say that clearly.
Useful Japanese to show:
胸やけや胃酸が上がる感じがあります。胃のむかつきもあります。
“I have heartburn or a feeling of acid coming up. I also feel queasy in my stomach.”
OTC Acid-Related Ingredients in Japan
1. Antacids: for acid already in the stomach
Antacids are ingredients that help neutralize stomach acid. Japanese labels may include:
- synthetic hydrotalcite
- magnesium aluminometasilicate
- dried aluminum hydroxide gel
- magnesium oxide or magnesium hydroxide
- calcium carbonate
- sodium bicarbonate
These ingredients may appear in products for heartburn, sour stomach, stomach discomfort, or indigestion. Some products also include digestive enzymes, herbal stomachic ingredients, or mucosal protectants, so do not judge the product by one ingredient alone.
2. Famotidine: an H2 blocker
Famotidine reduces acid secretion. In Japan, OTC famotidine products are Class 1 OTC medicines (第1類医薬品), so purchase requires pharmacist involvement.
Look for:
- Famotidine
- ファモチジン
Famotidine is not an antacid. It does not simply neutralize acid already in the stomach; it reduces acid production.
3. PPIs: lansoprazole, omeprazole, rabeprazole
PPI stands for proton pump inhibitor. In Japanese OTC products, you may see:
- Lansoprazole / ランソプラゾール
- Omeprazole / オメプラゾール
- Rabeprazole sodium / ラベプラゾールナトリウム
Current Japanese OTC PPI products are guidance-required medicines (要指導医薬品). A pharmacist must confirm whether the product is appropriate and explain how to use it.
PPIs are not general “strong stomach medicine” for any stomach problem. If your main symptom is unexplained nausea, repeated vomiting, strong abdominal pain, diarrhea, or motion sickness, tell pharmacy staff instead of assuming an acid medicine is the right match.
What to Tell Pharmacy Staff
Short, specific symptom descriptions help more than a vague “stomach problem.” You can show one or more of these lines:
| What you mean | Japanese to show |
| I have heartburn. | 胸やけがあります。 |
| I feel acid coming up. | 胃酸が上がってくる感じがあります。 |
| I have a sour or bitter taste in my mouth. | 口に酸っぱい、または苦い感じが上がってきます。 |
| It gets worse after meals. | 食後に悪化します。 |
| It gets worse when I lie down. | 横になると悪化します。 |
| I feel nauseous. | 吐き気があります。 |
| I am vomiting. | 嘔吐しています。 |
| I have chest pressure or chest pain. | 胸の圧迫感、または胸痛があります。 |
| I take other medicines. | 他に服用している薬があります。 |
| Should I see a doctor instead? | 市販薬ではなく、受診した方がよいですか？ |
For a broader pharmacy card, see Show This at a Japanese Pharmacy: OTC Medicine Questions in English and Japanese.
Small Things That May Help Mild Heartburn
If your symptoms are mild and familiar, these simple changes may help while you are traveling:
- Avoid foods or drinks that clearly trigger your own symptoms.
- If symptoms happen at night, finish eating at least three hours before lying down.
- Raise your head and upper back during sleep if reflux tends to happen at night.
- Avoid smoking, and consider whether alcohol is making symptoms worse.
Food triggers differ by person. You do not need to avoid every commonly mentioned food if it has never affected you.
FAQ
Can I buy heartburn medicine over the counter in Japan?
Yes. Japan has OTC antacid products, OTC famotidine products, and OTC PPI products. The purchase process differs by medicine category. Famotidine is Class 1 OTC, and current OTC PPIs are guidance-required medicines.
What is the best ingredient for heartburn in Japan?
There is no single “best” ingredient for everyone. Antacids, famotidine, and PPIs work differently. Use ingredient names as label clues, then ask pharmacy staff to check the product against your symptoms, age, health conditions, and other medicines.
What Japanese label words should I look for?
For heartburn or acid reflux medicine in Japan, useful label words include 胸やけ (heartburn), 胃酸 (stomach acid), 胃部不快感 (stomach discomfort), and むかつき (queasiness). The ingredient list is still important because many Japanese stomach medicines are combination products.
Does mukamuka mean I need heartburn medicine?
Not always. Mukamuka / むかつき can mean queasiness or stomach discomfort. If you also have burning, acid coming up, or a sour taste, mention those symptoms. If you mainly have nausea, vomiting, motion sickness, diarrhea, or strong pain, a heartburn product may not match.
Before You Buy or Use an OTC Product
Before using a Japanese OTC stomach medicine, check the package and insert for:
- してはいけないこと — things you must not do
- 相談すること — when to ask a doctor or pharmacist before use
- active ingredients and amount per dose
- age limits and dosage
- pregnancy or breastfeeding instructions
- warnings related to kidney, liver, heart, stomach, or duodenal disease
- allergies, previous side effects, prescription medicines, supplements, and other OTC medicines
Do not combine an antacid, famotidine product, PPI, or another stomach medicine on your own. Ask whether one product fits your full symptom pattern.
For Class 1 famotidine products and guidance-required PPI products, a pharmacist must handle the required confirmation. For other OTC stomach medicines, a pharmacist or registered seller may help you check the label.
If you are new to Japanese OTC medicine categories, see Drugstore Basics in Japan: How to Buy OTC Medicine Safely.
When to See a Doctor Instead of Adding More OTC Medicine
Seek medical care promptly if heartburn-like symptoms come with:
- trouble swallowing or pain when swallowing
- repeated or persistent vomiting
- vomit containing blood or material that looks like coffee grounds
- black, tarry stool or blood in the stool
- unexplained weight loss or loss of appetite
- severe or worsening upper-abdominal pain
- symptoms that keep returning or do not improve within the label’s time limit
Chest pain is not always heartburn. If you have pressure, squeezing, or severe chest pain, especially with shortness of breath, cold sweat, faintness, or pain spreading to the arm, shoulder, back, jaw, or neck, call 119 in Japan for an ambulance.
If it is not an ambulance situation but you are unsure how to find care, see How to See a Doctor in Japan as a Traveler.
This article is general information for travelers and residents in Japan. It does not diagnose your symptoms or recommend a specific product for you.
Related Guides
- Stomach and Digestive Problems in Japan: OTC Medicine Ingredients and Safety Checks
- Drugstore Basics in Japan: How to Buy OTC Medicine Safely
- Show This at a Japanese Pharmacy: OTC Medicine Questions in English and Japanese
- How to See a Doctor in Japan as a Traveler
References
- Ministry of Health, Labour and Welfare. Information on Japan’s OTC medicine sales system.
- Pharmaceuticals and Medical Devices Agency (PMDA). OTC and guidance-required medicine package insert search.
- Daiichi Sankyo Healthcare. Official Gaster 10 product information and package insert.
- Alinamin Pharmaceutical. Official Takepron S product information.
- Sato Pharmaceutical. Official Omepral S product information.
- Eisai. Official Pariet S product information and package insert.
- National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and causes of GER and GERD; treatment; eating, diet, and nutrition.
- National Heart, Lung, and Blood Institute. Heart attack symptoms.
- Japan National Tourism Organization. Guide for when you are feeling ill in Japan.
