Diphenhydramine in Japan (the ingredient of Benadryl): Drewell and Restamin
Diphenhydramine: how it is named on Japanese boxes, the 2 products in this database that contain it, how their doses compare with US labels, and the rules for bringing it into Japan and taking it home. On 3 October 2026, PMDA's search of OTC package inserts returned 682 products containing diphenhydramine (including creams and other salts).
要確認 ingredient
What it is called on Japanese boxes
How diphenhydramine is written on Japanese boxes, with the official English name from the JAN database or the Japanese Pharmacopoeia.
| Official English name | Name on Japanese boxes | Listed in |
|---|---|---|
| Diphenhydramine Hydrochloride | ジフェンヒドラミン塩酸塩 | JAN |
Diphenhydramine in Japanese products
The amount of diphenhydramine per dose and per day, as each package insert sets it.
On 3 October 2026, PMDA's search of OTC package inserts returned 682 products containing diphenhydramine (including creams and other salts).
| Product | Amount | Most a day for adults | Class on the box |
|---|---|---|---|
| Drewell | 50 mg per dose of 2 tablets | 50 mg (1 dose a day) | 第②類医薬品 |
| Restamin Kowa sugar-coated tablets | 30 mg per dose of 3 tablets | 90 mg (3 doses a day) | 第2類医薬品 |
Most a day for adults, by the package insert (mg)
Each package insert sets its own dose. Follow the directions and dosage on the box you buy.
Japanese doses and US labels
US doses come from the OTC labels on DailyMed.
| Product | Where | Amount | Most a day for adults |
|---|---|---|---|
| Drewell | Japan, package insert | 50 mg per dose of 2 tablets | 50 mg (1 dose a day) |
| Restamin Kowa sugar-coated tablets | Japan, package insert | 30 mg per dose of 3 tablets | 90 mg (3 doses a day) |
| Benadryl Allergy Ultratabs | US, OTC label | 25 mg per tablet | 300 mg (1 to 2 tablets, up to 6 times in 24 hours) |
| Benadryl Allergy Extra Strength | US, OTC label | 50 mg per tablet | 300 mg (1 tablet, up to 6 times in 24 hours) |
Follow the directions and dosage exactly.That is the wording of the Japanese package inserts. The table lines up what each product's own directions say; it is not a guide to how much to take.
The directions on the US labels, as printed
Bought with a check in Japan (要確認)
From 1 May 2026, medicines taken by mouth that contain diphenhydramine are designated abuse-prevention medicines (指定濫用防止医薬品).
Bringing it into Japan
Medicine with diphenhydramine that you bring for your own use counts towards Japan's supply limits for medicine.
Taking it home
Frequently asked questions
Is diphenhydramine sold over the counter in Japan?
On 3 October 2026, PMDA's search of OTC package inserts returned 682 products containing diphenhydramine (including creams and other salts). In this database: Drewell, Restamin Kowa sugar-coated tablets.
How much Diphenhydramine Hydrochloride is in Drewell?
50 mg per dose of 2 tablets, and at most 50 mg (1 dose a day) by its package insert.
How does Drewell compare with Benadryl Allergy Ultratabs?
Drewell: 50 mg per dose of 2 tablets, at most 50 mg (1 dose a day) (Japanese package insert). Benadryl Allergy Ultratabs: 25 mg per tablet, at most 300 mg (1 to 2 tablets, up to 6 times in 24 hours) (US label). Each product's directions apply only to that product.
Why does a Japanese shop check before selling diphenhydramine?
From 1 May 2026, medicines containing any of 8 ingredients are designated abuse-prevention medicines (指定濫用防止医薬品): ephedrine, codeine, dihydrocodeine, diphenhydramine, dextromethorphan, pseudoephedrine, bromovalerylurea and methylephedrine, with their hydrates and salts. Medicines for external use are not included.
Related items
PMDA package insert search (Japanese)
Sources for this page
- PMDA (Pharmaceuticals and Medical Devices Agency) OTC and guidance-required drug package insert search (一般用医薬品・要指導医薬品 添付文書等情報検索)checked October 3, 2026
- National Institute of Health Sciences Japanese Accepted Names for Pharmaceuticals (JAN) databasechecked October 3, 2026
- PMDA (Pharmaceuticals and Medical Devices Agency) ドリエル: package insert (添付文書)checked October 3, 2026
- PMDA (Pharmaceuticals and Medical Devices Agency) レスタミンコーワ糖衣錠: package insert (添付文書)checked October 3, 2026
- DailyMed (US National Library of Medicine) Benadryl Allergy: Benadryl Allergy Ultratabs labelchecked October 3, 2026
- DailyMed (US National Library of Medicine) Benadryl Allergy: Benadryl Allergy Extra Strength labelchecked 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
- Ministry of Health, Labour and Welfare Designated abuse-prevention medicines, Notice No. 32 of 2026 (告示第32号)checked October 3, 2026
- Ministry of Health, Labour and Welfare Quantity for designated abuse-prevention medicines, Notice No. 33 of 2026 (告示第33号)checked October 3, 2026
- Ministry of Health, Labour and Welfare Selling designated abuse-prevention medicines (医薬発1226第16号, 26 December 2025)checked October 3, 2026
- Ministry of Health, Labour and Welfare Q&A on selling designated abuse-prevention medicines (30 January 2026)checked October 3, 2026
Compiled by Japan Japan !! · Updated October 3, 2026