Pirfenidone is an orally administered antifibrotic agent, specifically indicated for the treatment of mild to moderate Idiopathic Pulmonary Fibrosis (IPF). It is a pyridone derivative that modulates multiple pathways involved in fibrosis, including TGF-β and TNF-α. In the Indian context, it is a critical therapy for slowing disease progression in IPF, a condition with limited treatment options and poor prognosis.
Adult: The recommended maintenance dose is 2403 mg per day administered as three divided doses (801 mg three times daily). For the 400 mg tablet formulation: Take ONE 400 mg tablet three times daily (total 1200 mg/day) PLUS ONE 267 mg capsule three times daily (total 801 mg/day) to achieve the 2403 mg total. Alternatively, three 267 mg capsules three times daily (total 2403 mg/day).
Note: ALWAYS TAKE WITH FOOD to reduce gastrointestinal upset (nausea, dyspnea). Swallow tablet/capsule whole with a full glass of water. Dose Titration: Week 1: 801 mg/day (267 mg three times daily). Week 2: 1602 mg/day (534 mg three times daily). Week 3 onwards: Full maintenance dose of 2403 mg/day. If GI side effects occur, temporary dose reduction or interruption is recommended, followed by re-titration.
The exact mechanism is not fully elucidated. Pirfenidone exhibits antifibrotic, anti-inflammatory, and antioxidant properties. It downregulates the production of growth factors and procollagens I and III. It inhibits the profibrotic cytokine Transforming Growth Factor-beta (TGF-β), which is a key driver of fibroblast proliferation and collagen deposition in IPF. It also reduces the production of Tumor Necrosis Factor-alpha (TNF-α), a pro-inflammatory cytokine.
Pregnancy: Pregnancy Category C. Animal studies have shown fetal toxicity (embryolethality, teratogenicity). There are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus. Women of childbearing potential should use effective contraception.
Driving: Pirfenidone may cause dizziness and fatigue. Patients should be cautioned about operating machinery or driving until they are certain the medication does not affect them adversely.
| Fluvoxamine (strong CYP1A2 inhibitor) | Markedly increases pirfenidone exposure (AUC). Increases risk of side effects. | Major - Avoid combination. If unavoidable, reduce pirfenidone dose. |
| Ciprofloxacin (moderate CYP1A2 inhibitor) | Increases pirfenidone exposure. | Moderate - Monitor for adverse effects. |
| Rifampicin, Omeprazole, Smoking (CYP1A2 inducers) | Decreases pirfenidone exposure, potentially reducing efficacy. | Major - Advise patients to stop smoking. Monitor efficacy; may need dose adjustment with other inducers. |
| Other photosensitizing drugs (e.g., Doxycycline, Ciprofloxacin, Thiazides) | Additive risk of photosensitivity reactions. | Moderate - Advise strict sun protection. |
| Antacids (Aluminum/Magnesium based) | No significant interaction expected. Can be used for dyspepsia. | Minor |