Gaster 10 (ガスター10): ingredients, dose and warnings in English
Gaster 10 (ガスター10) is sold in Japan as a class 1 medicine: the box reads 第1類医薬品. In 1 tablet: Famotidine 10 mg. The package insert sets the adult dose at 1 tablet, up to 2 times a day, for ages 15 and over and under 80.
第1類医薬品 · Class 1Pharmacist only
What is in Gaster 10
The package insert lists 1 active ingredient in 1 tablet. The middle column is how each one is written on the Japanese box.
| Ingredient | Name on the box | Amount |
|---|---|---|
| Famotidine | ファモチジン | 10 mg |
Additives, as written on the package insert (Japanese)
リン酸水素カルシウム,セルロース,乳糖,ヒドロキシプロピルセルロース,トウモロコシデンプン,無水ケイ酸,ステアリン酸カルシウム,白糖,乳酸カルシウム,マクロゴール,酸化チタン,タルク,カルナウバロウ
The maker publishes an English package insert for Gaster 10: Daiichi Sankyo Healthcare: Gaster 10 (English package insert). This page translates the current Japanese package insert on PMDA.
Source: PMDA (Pharmaceuticals and Medical Devices Agency) — ガスター10: package insert (添付文書) · Daiichi Sankyo Healthcare — Gaster 10: English package insert
What the package insert lists it for
The approved wording of the Japanese package insert, translated. It is what the product is sold for, not advice on what to take.
- Stomach pain, heavy stomach, heartburn, queasiness
- (This medicine contains an H2 blocker)
Do not take this medicine for symptoms other than those stated under the indications.
The dose, as written on the package insert
Translated line by line from the directions and dosage (用法・用量) section.
- Famotidine per dose
- 10 mg
- Adult dose
- 1 tablet
- Doses a day
- Up to 2
- Age
- 15 and over and under 80
- When symptoms of stomach pain, heavy stomach, heartburn or queasiness appear, take the following amount with water or warm water.
| Age | Single dose | Doses a day |
|---|---|---|
| Adults (15 and over, under 80) | 1 tablet | Up to 2 times |
| Children (under 15) | Do not take | |
| Older people (80 and over) | Do not take |
- If the symptoms have not subsided 8 hours or more after taking it, take 1 more tablet.
- If the symptoms have subsided, stop taking it.
- If your symptoms do not improve after taking it for 3 days, stop taking it and ask a doctor or pharmacist for advice.
- Do not keep taking it for more than 2 weeks.
Notes on the directions
- (1) Follow the directions and dosage exactly.
- (2) When taking this medicine, refrain from drinking alcoholic beverages.
- (As a general rule, medicines are not taken together with alcoholic beverages)
- [How to take out the tablets]
- Press the raised part of the PTP sheet containing the tablet firmly with your fingertip to break the aluminium foil on the back, then remove the tablet and take it. (Accidentally swallowing it as it is can lead to unexpected accidents, such as it piercing the mucous membrane of the oesophagus)
Do not
The package insert opens with what you must not do.
(If you do not follow these, your current symptoms may get worse, and side effects become more likely)
1. Do not take it if you are one of the following people.
- (1) People who have had allergic symptoms (for example, rash/redness, itching, swelling of the throat, eyelids, lips, etc.) caused by H2 blockers such as Famotidine
- (2) People who are receiving treatment for the following diseases, or being given the following medicines, at a medical institution
- Blood disease, kidney/liver disease, heart disease, gastric/duodenal disease, immune system diseases such as asthma or rheumatism, steroids, antibiotics, anticancer drugs, azole antifungals
- (It may cause a decreased white blood cell count, a decreased platelet count, etc.)
- (If you have kidney/liver disease, the excretion of the medicine may be delayed and its effect may appear more strongly)
- (If you have a heart disease such as myocardial infarction, valvular heart disease or cardiomyopathy, an irregular pulse accompanied by electrocardiogram abnormalities may appear)
- (People who are receiving treatment for gastric/duodenal disease are highly likely to have been prescribed Famotidine or a similar medicine, so care is needed to avoid duplicate use)
- (The absorption of azole antifungals decreases and their effect is weakened)
- (3) People who have ever been told by a doctor that they have a blood abnormality, such as a low red blood cell count (anaemia), a low platelet count (bleeding that is hard to stop, bleeding easily) or a low white blood cell count
- (This medicine may act as a trigger and cause a blood abnormality again)
- (4) Children (under 15) and older people (80 and over)
- (5) Women who are pregnant or think they may be pregnant
2. Do not take the following medicines while taking this medicine.
- Other gastrointestinal medicines
3. Women who are breastfeeding: do not take this medicine, or avoid breastfeeding if you take it.
Ask a doctor, pharmacist or registered salesperson
The package insert says to ask for advice in these cases.
1. If you are one of the following people, ask a doctor or pharmacist for advice before taking it.
- (1) People who are receiving treatment from a doctor, or people who are taking other medicines
- (2) People who have had allergic symptoms caused by medicines etc.
- (3) Older people (65 and over)
- (In general, older people may have reduced physiological functions)
- (4) People who have the following symptoms
- Sore throat, cough and high fever (people who have these symptoms are suspected of having a serious infection, and blood abnormalities such as a decreased blood cell count may be found. If you have such symptoms before taking it, taking this medicine may make the symptoms worse, and you may also be late in noticing the side effects of this medicine), weight loss of unknown cause, persistent abdominal pain (another disease may be the cause)
2. If the following symptoms appear after taking it, they may be side effects, so stop taking it immediately and ask a doctor or pharmacist for advice, taking this leaflet with you.
Possible side effects, by part of the body
- Skin
- rash/redness, itching, swelling
- Circulatory system
- irregular pulse
- Nervous system
- a feeling of faintness, fits (convulsions)
- Other
- abnormalities in physical condition appear, such as feeling unwell, feeling tired, or having a fever and a sore throat.
- In rare cases the following serious symptoms may occur. If they do, see a doctor immediately.
Rare but serious symptoms: name and signs
- Shock (anaphylaxis)
- right after taking it, itchy skin, hives, hoarseness, sneezing, itchy throat, difficulty breathing, palpitations, clouding of consciousness, etc. appear.
- Oculomucocutaneous syndrome (Stevens-Johnson syndrome)
- high fever, bloodshot eyes, eye discharge, sores on the lips, sore throat, widespread rash/redness on the skin, etc. continue or rapidly get worse.
- Toxic epidermal necrolysis
- high fever, bloodshot eyes, eye discharge, sores on the lips, sore throat, widespread rash/redness on the skin, etc. continue or rapidly get worse.
- Rhabdomyolysis
- pain in the muscles of the arms and legs, shoulders, lower back, etc., numbness in the arms and legs, loss of strength, stiffness, the whole body feeling tired, reddish-brown urine, etc. appear.
- Liver dysfunction
- fever, itching, rash, jaundice (the skin and the whites of the eyes turn yellow), brown urine, tiredness all over the body, loss of appetite, etc. appear.
- Kidney disorder
- fever, rash, decreased amount of urine, oedema all over the body, tiredness all over the body, joint pain (aching joints), diarrhoea, etc. appear.
- Interstitial pneumonia
- shortness of breath/difficulty breathing when climbing stairs or exerting yourself a little, dry cough, fever, etc. are seen, and these appear suddenly or continue.
- Blood disorder
- sore throat, fever, tiredness all over the body, the face and the inside of the eyelids looking whitish, bleeding easily (bleeding gums, nosebleeds, etc.), bruising (the colour does not fade when pressed), etc. appear.
3. If you have accidentally taken more than the specified dose, stop taking it immediately and ask a doctor or pharmacist for advice, taking this leaflet with you.
4. The following symptoms may appear after taking it, so if these symptoms continue or get worse, stop taking it and ask a doctor or pharmacist for advice, taking this leaflet with you.
- Constipation, loose stools, diarrhoea, dry mouth
Who can sell it in Japan
The Gaster 10 box carries the class 第1類医薬品, which decides who may sell it.
- On the box
- 第1類医薬品 (Class 1). The box reads 第1類医薬品.
- Who can sell it
- Only a pharmacist may sell it.
- Information when you buy
- The pharmacist must give the information in writing (on paper or on a screen). This can be skipped if you say you do not need it and the pharmacist judges you will use it properly.
Source: e-Gov law search (Digital Agency, Japan) — Pharmaceutical and Medical Device Act (医薬品医療機器等法), current text · e-Gov law search (Digital Agency, Japan) — Enforcement Regulations of the Pharmaceutical and Medical Device Act (施行規則), current text
Taking it home
Frequently asked questions
How much Famotidine is in Gaster 10?
10 mg in a dose of 1 tablet, according to the Japanese package insert.
How much Gaster 10 can an adult take in a day?
The package insert sets the adult dose at 1 tablet, up to 2 times a day. Doses are at least 8 hours apart.
Can children take Gaster 10?
No. The package insert says it is not to be taken under 15.
Do I need a pharmacist to buy Gaster 10?
Gaster 10 is a class 1 medicine (第1類医薬品). Only a pharmacist may sell it.
What is Gaster 10 called in Japanese?
ガスター10. The Gaster 10 box also carries the class 第1類医薬品.
Related items
Package insert in Japanese: PMDA
Sources for this page
- PMDA (Pharmaceuticals and Medical Devices Agency) ガスター10: package insert (添付文書)checked October 3, 2026
- Daiichi Sankyo Healthcare Gaster 10: English package insertchecked October 3, 2026
- e-Gov law search (Digital Agency, Japan) Pharmaceutical and Medical Device Act (医薬品医療機器等法), current textchecked October 3, 2026
- e-Gov law search (Digital Agency, Japan) Enforcement Regulations of the Pharmaceutical and Medical Device Act (施行規則), current textchecked October 3, 2026
Compiled by Japan Japan !! · Updated October 3, 2026