1. Clinical Overview
Febuxostat is a potent, selective, non-purine xanthine oxidase inhibitor used for the long-term management of hyperuricemia in patients with gout. It is a second-line agent after allopurinol intolerance or failure. Unlike allopurinol, it is not a purine analogue and does not require dose adjustment in mild-to-moderate renal impairment, making it a significant option in the Indian context where renal comorbidities are common.
| Onset | Duration | Bioavailability |
|---|---|---|
| Serum uric acid reduction begins within 2 hours of administration, with significant reduction observed within 1-2 weeks. | Approximately 24 hours, supporting once-daily dosing. | Approximately 49% (oral). |
2. Mechanism of Action
Febuxostat is a non-purine selective inhibitor of xanthine oxidase (XO), the enzyme responsible for the conversion of hypoxanthine to xanthine and xanthine to uric acid. By inhibiting XO, it reduces the production of uric acid, thereby lowering serum urate concentrations.
3. Indications & Uses
- Chronic management of hyperuricemia in patients with gout
4. Dosage & Administration
Adult Dosage: Recommended starting dose is 20mg or 40mg once daily. The 20mg dose is recommended for patients with mild hyperuricemia or as a starting dose to assess tolerability. Dose may be increased to 40mg or 80mg daily if target sUA (<6 mg/dL) is not achieved after 2-4 weeks.
Administration: Administer orally once daily, with or without food. Tablet should be swallowed whole with a glass of water. Consistent daily timing is recommended. Prophylaxis for gout flares with NSAID or colchicine should be initiated concurrently and continued for up to 6 months.
5. Side Effects
Common side effects may include:
- Liver function abnormalities (increased ALT, AST)
- Nausea
- Headache
- Rash
- Arthralgia
- Gout flare (especially during initiation)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Azathioprine | Increased levels/toxicity of azathioprine due to xanthine oxidase inhibition | Contraindicated |
| Mercaptopurine (6-MP) | Increased levels/toxicity of mercaptopurine due to xanthine oxidase inhibition | Contraindicated |
| Theophylline | Increased theophylline levels, risk of toxicity | Contraindicated |
| Didanosine | Potential increased toxicity; avoid concomitant use | Major |
| NSAIDs (e.g., Naproxen, Diclofenac) | Increased risk of NSAID-related adverse effects; used together for gout flare prophylaxis | Moderate |
| Colchicine | No significant PK interaction, but used together therapeutically. Monitor for colchicine toxicity, especially in renal impairment. | Moderate |
| Warfarin | Potential for increased INR; monitor INR closely when initiating or discontinuing febuxostat. | Moderate |
7. Patient Counselling
- DO take the tablet once daily as prescribed, with or without food.
- DO continue taking your medication even if you have a gout attack. Do not stop febuxostat during a flare.
- DO take prophylactic medication (NSAID/colchicine) as advised by your doctor to prevent initial flares.
- DO maintain adequate hydration (drink 2-3 liters of water daily).
- DONT take the medication if you are also taking azathioprine, mercaptopurine, or theophylline.
- DONT consume excessive alcohol.
- DONT start febuxostat during an acute gout attack; wait until the attack resolves.
8. Toxicology & Storage
Overdose: Limited data. Potential symptoms may include nausea, vomiting, diarrhea, abdominal pain, and elevated liver enzymes. Severe overdose could theoretically lead to profound hypouricemia and increased xanthine excretion, with risk of xanthine nephropathy or crystalluria.
Storage: Store at room temperature (15-30°C), protected from light and moisture. Keep the container tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.