Tegonat 20 mg (Tegafur / Gimeracil / Oteracil): Precise S‑1 Oral Chemotherapy for Gastric & Colorectal Cancer

Tegonat 20 mg is a fixed-dose formulation of the oral chemotherapy combination commonly known as S‑1, comprising tegafur (20 mg), gimeracil (5.8 mg), and oteracil potassium (15.8 mg), manufactured by Natco Pharma in India. 

🎯 Therapeutic Indications

• Indicated for advanced or metastatic gastric (stomach) cancer in combination with cisplatin.
• Used as monotherapy or in combinations (e.g. with oxaliplatin, irinotecan) for metastatic colorectal cancer, especially when standard fluoropyrimidines are poorly tolerated. 

⚙️ How It Works (Mechanism of Action)

Tegafur is a prodrug of 5‑fluorouracil (5‑FU). Gimeracil selectively inhibits dihydropyrimidine dehydrogenase (DPD) to prolong systemic 5‑FU levels, while oteracil mitigates gastrointestinal toxicity by limiting 5‑FU activation in the gut—striking a balance between efficacy and tolerability. The tolerable 1:0.4:1 tegafur:gimeracil:oteracil molar ratio optimizes systemic exposure and reduces GI effects. 

🩺 Dosing & Administration Guidelines

• Dose is based on body surface area (typically 25 mg/m² tegafur)—in clinical practice this often equals 2 capsules (40 mg) given every 12 hours for 21 consecutive days, followed by a 7‑day rest in a 28‑day cycle. 
• Administer on an empty stomach—at least 1 hour before or after a meal with water. 
• Do not crush, chew, or open capsules. Swallow intact. 
• Missed doses: if vomiting within 15 minutes of ingestion, repeat once; otherwise skip the dose and continue the schedule—never double dose. 

⚠️ Adverse Effects & Safety Monitoring

• Hematologic toxicity: very common—neutropenia, anemia, leukopenia, thrombocytopenia; often dose-limiting and requiring periodic CBC monitoring. 
• Gastrointestinal & Constitutional: diarrhea, nausea, vomiting, mucositis/stomatitis, anorexia, weight loss, fatigue. 
• Electrolyte imbalances, dehydration, lacrimation, neuropathy, and rare cardiac arrhythmias. 
• Serious Grade 3–4 toxicities (≥10%): neutropenia, anemia, fatigue. ([turn1search4])
• Risk groups: patients with dihydropyrimidine dehydrogenase (DPD) deficiency have significantly higher risk of toxicity—including fatal myelosuppression and neurotoxicity. 

🔐 Contraindications & Drug Interactions

• Contraindicated in patients with complete or partial DPD deficiency, hypersensitivity to fluoropyrimidines, severe bone marrow suppression, pregnancy, or breastfeeding.
• Avoid live vaccines during therapy and for several months after completion due to immunosuppressive risk. 
• Caution with warfarin or other coumarin anticoagulants, phenytoin, methotrexate, or brivudine—monitor INR and liver enzymes closely. 

✅ Why Choose Tegonat 20 mg?

• As a generic version of Teysuno (15 mg & 20 mg capsule strengths), Tegonat provides high efficacy at a more affordable cost. 
• Fixed 20 mg capsule strength enables precise BSA-based dosing for adults. 
• Oral administration twice daily offers convenience and improves outpatient compliance versus IV fluoropyrimidines. 

❓ Frequently Asked Questions (FAQs)

1. Why is Hepatitis B screening recommended?

Fluoropyrimidines like S‑1 may reactivate latent hepatitis B. Baseline serology (HBsAg/HBcAb) and monitoring are essential for patients at risk. 

2. Can Tegonat 20 mg be co-administered with oxaliplatin or other agents?

Yes—clinical protocols support combinations with cisplatin, oxaliplatin, or irinotecan depending on cancer type; always adhere to your oncologist’s regimen and adjust doses as needed. 

3. What if I have renal or liver dysfunction?

Use with caution in severe impairment—gimeracil clearance is reduced in renal dysfunction, increasing 5‑FU exposure. Dose modifications may be necessary. 

4. When will treatment response be assessed?

Response is usually evaluated after 2–3 treatment cycles (6–8 weeks)—via imaging or tumor marker changes. Benefits often accrue over multiple cycles. 

5. How long should contraception be continued?

Effective contraception is required during treatment and for at least 6 months afterward in both men and women—teratogenic risk is high.