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Prescription only medicine

S-one Trio 15 mg Capsules

Gimeracil, Oteracil, Tegafur · Generic equivalent of Teysuno

S-one Trio 15 mg Capsules is a trusted medication containing Gimeracil, Oteracil and Tegafur, designed for personal use under the guidance of a healthcare professional. Available for prescription-based international supply with discreet worldwide delivery.

Active ingredients
Gimeracil, Oteracil, Tegafur
Strength
15 mg / 4.35 mg / 11.8 mg
Form
Capsule
Manufacturer
Intas Pharmaceuticals Ltd.
Made in
India
Prescription
Required
Commonly used forColorectal Cancer
$99.00 per pack of 7 capsules

Prescription required — upload it at checkout.

Generic equivalent of Teysuno — up to 80% less than the branded price

Verified pharmacy Genuine medication Tracked shipping Medically reviewed by Chitra Shetty
Licensed Pharmacy Trust & safety
Licensed Manufacturers Every medicine from a licensed manufacturer
Dedicated Oncology Team Doctor + pharmacist review every order before dispatch
Worldwide Delivery UK · US · AU · EU · NZ — tracked and insured
About this medicine

What is S-one Trio 15 mg Capsules?

S-1 is an oral chemotherapy capsule that combines three ingredients. Tegafur is converted in the body into 5-fluorouracil (5-FU), one of the most widely used chemotherapy drugs. Gimeracil slows the breakdown of 5-FU so that steady levels are reached from a tablet rather than an infusion, and oteracil stays in the gut to reduce the diarrhoea and mouth soreness 5-FU can cause.

It is approved in Europe (as Teysuno) for advanced stomach cancer, taken together with cisplatin, and is used in Japan, India and other countries for stomach, pancreatic, bowel, head-and-neck and some lung cancers under specialist protocols. It is not approved in the United States.

The strength on the pack (15 mg or 20 mg) refers to the tegafur component. S-1 is taken twice a day after meals, typically for 21 days followed by a 7-day break, with the dose calculated from your body surface area. It is a prescription-only medicine; a valid prescription must be provided at checkout.

How it works

How does Tegafur + Gimeracil + Oteracil work?

Tegafur is a 'prodrug': on its own it does little, but the liver converts it into 5-fluorouracil. 5-FU is a fake building block that cancer cells try to use when copying their DNA and RNA; once inside, it jams the enzyme thymidylate synthase and corrupts RNA, and the dividing cell dies. The problem with 5-FU is that the body destroys most of it within minutes. Gimeracil blocks the enzyme responsible (DPD), so 5-FU levels from an oral dose stay steady for hours. Oteracil is not absorbed well and acts mainly in the bowel lining, where it stops 5-FU being activated — protecting the gut from some of the diarrhoea and inflammation 5-FU causes elsewhere.

Prodrug conversion

Tegafur is converted by liver enzymes (CYP2A6) into 5-fluorouracil.

Sustained levels

Gimeracil inhibits dihydropyrimidine dehydrogenase (DPD), the enzyme that would otherwise clear 5-FU within minutes, so blood levels stay in the effective range.

Targeted effect

5-FU blocks thymidylate synthase and is built into RNA in dividing tumour cells, which then die; oteracil limits activation in the gut lining to reduce bowel side effects.

Uses

What is Tegafur + Gimeracil + Oteracil used for?

Advanced gastric (stomach) cancer

In combination with cisplatin, in adults. Also used after surgery (adjuvant) under Japanese and Asian guidelines.

EMA CDSCO
Pancreatic, colorectal, head-and-neck and non-small cell lung cancer

Approved in Japan and used in some other countries; not approved for these uses by the EMA or FDA. Only under specialist supervision within an established protocol.

Off-label

Only your oncologist can determine whether this medicine is right for your diagnosis. The above is for information only.

Dosage

How to take S-one Trio 15 mg Capsules

Your oncologist will prescribe your exact dose. The right dose for you depends on your weight, kidney and liver function, and — for some medicines — your genetic test results.

Always take exactly as prescribed. Do not change your dose or stop taking this medicine without speaking to your doctor first, even if you feel well.

Missed a dose? Skip a missed dose and take the next one at the usual time. Do not double up. Tell your team if you vomit repeatedly.

With food? Take within one hour after food with water. Swallow capsules whole; do not open. Avoid folinic acid (leucovorin) supplements unless prescribed with it.

Important safety information

Safety & warnings

Please read this section before taking S-one Trio 15 mg Capsules and discuss any concerns with your oncologist.

Common side effects

Side effects affect some people, not everyone. Most are manageable — let your treatment team know about anything that concerns you.

  • Low white blood cells (neutropenia) and anaemia
  • Diarrhoea
  • Nausea, vomiting, reduced appetite
  • Tiredness (fatigue)
  • Mouth soreness (stomatitis)
  • Skin darkening (pigmentation), rash, dry skin
  • Watery eyes and tear-duct narrowing
  • Taste changes
  • Hand-foot syndrome

Contact your doctor immediately if you notice:

  • Fever of 38°C or higher, chills or signs of infection Go to the emergency department — neutropenic infection is a medical emergency.
  • Diarrhoea more than four times a day, or with blood or dehydration Stop the capsules and contact your team the same day.
  • Mouth ulcers that stop you eating or drinking Stop and contact your team.
  • Chest pain, palpitations or breathlessness Seek emergency care — 5-FU can rarely cause coronary spasm.
  • Confusion, unsteadiness, slurred speech Seek urgent review — rare but reported with fluoropyrimidines.
  • Yellow skin or eyes, dark urine Contact your doctor immediately — possible liver injury.

Important: tell your doctor about these medicines

Taking Tegafur + Gimeracil + Oteracil with certain other medicines can be dangerous. Always tell every doctor, dentist, and pharmacist about all medicines you are taking.

  • Other fluoropyrimidines (capecitabine, 5-FU infusion) and DPD inhibitors Critical

    Severe, potentially fatal toxicity from doubled 5-FU exposure.

  • Brivudine and sorivudine (antivirals) Critical

    Profound DPD inhibition — fatal 5-FU toxicity has occurred.

  • Warfarin Major

    Markedly increased INR and bleeding risk.

  • Phenytoin Major

    Phenytoin levels rise; toxicity reported with fluoropyrimidines.

  • Live vaccines Major

    Risk of serious infection while immunosuppressed.

Pregnancy & breastfeeding

S-1 can harm an unborn baby and must not be used in pregnancy. Women who could become pregnant should use effective contraception during treatment and for at least six months after the last dose.

Do not breastfeed during treatment.

Fluoropyrimidines may impair fertility. Discuss sperm banking or egg/embryo freezing before your first dose if relevant.

For full prescribing information see: EMA: Teysuno — European public assessment report and product information

Storage

How to store S-one Trio 15 mg Capsules

Temperature

Store below 25°C (77°F) in the original blister.

Light & moisture

Protect from moisture; keep blisters intact until use.

Keep away from children

Keep out of the sight and reach of children.

Safe handling

Cytotoxic medicine: swallow capsules whole, never open them; wash hands after handling. Carers should avoid direct contact. Return unused capsules to a pharmacy.

Travelling

Carry in original packaging with your prescription and an oncologist's letter. S-1 is not licensed in the United States — check import rules for your destination before travelling with it.

Reviewed for accuracy

Medically reviewed content

Chitra Shetty

Chitra Shetty

B.Pharm, M.Pharm

Chitra Shetty is a licensed clinical pharmacist with 14 years of experience. She holds a B.Pharm and M.Pharm from Sambalpur University. At OnlineMeds, she reviews medicine and health content to help ensure it is accurate, evidence-based, and easy to understand.

Our commitment to you

How we support oncology patients

We understand that accessing the right cancer medicine can feel overwhelming. Here is what you can expect from us.

Personal oncology support

Every enquiry is reviewed by our oncology doctor and pharmacist team — not an automated system.

Genuine, verified medicine

Sourced exclusively from licensed pharmaceutical manufacturers. Every batch is traceable from origin to your door.

Prescription checked before dispatch

We verify every prescription with our internal medical team. No shortcuts, no exceptions.

Cold-chain logistics

Temperature-sensitive medicines shipped with appropriate packaging to maintain integrity.

Discreet, plain packaging

No pharmacy branding or product name on the outer packaging.

Up to 80% less than branded

Generic oncology medicines contain the same active ingredient as the originator brand — at a fraction of the cost.

FAQ

Frequently asked questions

Why does S-one Trio 15 mg Capsules contain three ingredients?

Only one — tegafur — is the anticancer drug; it turns into 5-fluorouracil in the body. Gimeracil keeps 5-FU from being destroyed too fast, so a capsule can replace an infusion. Oteracil stays in the gut and reduces the diarrhoea and mouth soreness 5-FU can cause. Together they are known as S-1.

[1] EMA: Teysuno — European public assessment report and product information

What does the "15 mg" or "20 mg" on the pack refer to?

The tegafur component. Each capsule contains tegafur plus fixed proportions of gimeracil and oteracil. Your dose is calculated from your body surface area and rounded, so you may be prescribed a mix of both strengths.

[1] EMA: Teysuno — European public assessment report and product information

Is S-one Trio 15 mg Capsules approved in my country?

S-1 is approved in the European Union (as Teysuno), Japan and India, among others, but not in the United States. Where you live affects whether it can be legally imported for personal use — your prescriber and our pharmacist team can advise.

[1] EMA: Teysuno — European public assessment report and product information

How is S-one Trio 15 mg Capsules different from capecitabine?

Both are oral medicines that become 5-FU in the body. Capecitabine relies on tumour enzymes for its final activation; S-1 instead blocks the breakdown of 5-FU (gimeracil) and protects the gut (oteracil). They are never taken together, and a washout period is needed when switching.

[2] NCI Drug Dictionary: Tegafur-gimeracil-oteracil potassium (S-1)

What is DPD deficiency and why does it matter?

DPD is the enzyme that clears 5-FU. People born with very low DPD activity can suffer life-threatening toxicity from any fluoropyrimidine. Many centres now test for DPD (DPYD gene) before starting; complete deficiency is a contraindication. Ask your team whether you have been tested.

[3] Electronic Medicines Compendium (UK): Teysuno capsules SmPC

Is S-one Trio 15 mg Capsules the same as Teysuno?

S-one Trio 15 mg Capsules contains the same three active ingredients in the same fixed ratio as the originator product Teysuno / TS-1. Generic medicines must meet the same regulatory standards for quality, safety and effectiveness. Used as prescribed by a licensed medical professional.

[1] EMA: Teysuno — European public assessment report and product information

Why must I take it after meals?

Taking S-1 within an hour after eating is how it was studied; an empty stomach changes the absorption of the three components relative to each other. Morning and evening meals are the usual anchors.

[1] EMA: Teysuno — European public assessment report and product information

Do I need a prescription to order S-one Trio 15 mg Capsules?

Yes. S-1 is prescription-only. Upload your oncologist's prescription at checkout; our pharmacist team reviews it before dispatch. Used as prescribed by a licensed medical professional.

Sources

References

  1. 1. EMA: Teysuno — European public assessment report and product information. https://www.ema.europa.eu/en/medicines/human/EPAR/teysuno European Medicines Agency. Accessed 12 Sep 2026.
  2. 2. NCI Drug Dictionary: Tegafur-gimeracil-oteracil potassium (S-1). https://www.cancer.gov/publications/dictionaries/cancer-drug/def/tegafur-gimeracil-oteracil-potassium National Cancer Institute. Accessed 12 Sep 2026.
  3. 3. Electronic Medicines Compendium (UK): Teysuno capsules SmPC. https://www.medicines.org.uk/emc/search?q=teysuno Accessed 12 Sep 2026.
Medical disclaimer: This content is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional — specifically your oncologist — before starting, changing, or stopping any medication. Information is based on EMA EPAR Teysuno (not FDA-approved), NCI Drug Information, and NHS patient information.
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