Adult: Initially, 267 mg tid for 7 days, then increase dose to 534 mg tid for 7 days, then to usual maintenance dose: 801 mg tid. Max: 2403 mg daily. Adjust dosage according to toxicity.
Special Patient Group
Patient concomitantly using strong CYP1A2 inhibitors (e.g. enoxacin, fluvoxamine): 267 mg tid.
Patient concomitantly using ciprofloxacin at a dosage of 750 mg bid: 534 mg tid.
Renal Impairment
ESRD requiring haemodialysis: Contraindicated.
CrCl (mL/min)
Dosage
<30
Contraindicated.
Hepatic Impairment
Severe (Child-Pugh class C): Contraindicated.
Contraindications
Severe hepatic and renal impairment, ESRD requiring haemodialysis.
Special Precautions
Smokers. Mild to moderate hepatic and renal impairment. Pregnancy and lactation. Patient taking fluvoxamine and ciprofloxacin.
Adverse Reactions
Significant: Nausea, vomiting, diarrhoea, dyspepsia, GERD, abdominal pain, photosensitivity, weight loss, dizziness, increased ALT/AST, angioedema. Rarely, hyperbilirubinaemia. Gastrointestinal disorders: Constipation, flatulence, gastritis. General disorders and administration site conditions: Fatigue, asthenia, lethargy, non-cardiac chest pain. Investigations: Increased γ-glutamyl transferase. Metabolism and nutrition disorders: Anorexia, decreased appetite. Musculoskeletal and connective tissue disorders: Myalgia, arthralgia. Nervous system disorders: Headache, dysgeusia. Psychiatric disorders: Insomnia, somnolence. Renal and urinary disorders: UTI. Respiratory, thoracic and mediastinal disorders: Dyspnoea, cough, upper respiratory tract infection. Skin and subcutaneous tissue disorders: Rash, pruritus, erythema, dry skin, sunburn. Vascular disorders: Hot flush.
Patient Counseling Information
Avoid smoking. This drug may cause dizziness and fatigue, if affected, do not drive or operate machinery. Avoid excessive exposure to sun and UV light.
Monitoring Parameters
Perform LFT before initiation of treatment, monthly for the 1st 6 months and quarterly, thereafter. Monitor weight; signs and symptoms of gastrointestinal and photosensitivity reactions.
Drug Interactions
Increased toxicity with strong (e.g. fluvoxamine) and moderate (e.g. ciprofloxacin) CYP1A2 inhibitors. Decreased efficacy with CYP1A2 inducers (e.g. omeprazole).
Food Interaction
Decreased absorption with food. May increase toxicity with grapefruit juice.
Action
Description: Mechanism of Action: Pirfenidone, a synthetic pyridone, is an antifibrotic agent. Its exact mechanism of action is still unknown. In idiopathic pulmonary fibrosis, it may decrease the amount of pro-inflammatory cells [e.g. interleukin-1-β (IL-1β), IL-6, tumour necrosis factor-α (TNF-α)] and the production of fibroblast and of fibrosis-associated proteins and cytokines. It may also decrease accumulation of extracellular matrix and lung fibrosis due to transforming growth factor-β (TGF-β) and platelet derived growth factor (PDGF). Pharmacokinetics: Absorption: Absorbed from the gastrointestinal tract. Decreased absorption with food. Time to peak plasma concentration: 30 minutes to 4 hours. Distribution: Volume of distribution: Approx 59-71 L. Plasma protein binding: 50-58% mainly to albumin. Metabolism: Metabolised in the liver mainly by CYP1A2 and to a lesser extent by CYP2C9, 2C19, 2D6 and 2E1 into metabolites including 5-carboxy-pirfenidone. Excretion: Mainly via urine (approx 80%; >95% as 5-carboxy-pirfenidone and <1% as unchanged drug). Terminal elimination half-life: Approx 3 hours.
Chemical Structure
Pirfenidone Source: National Center for Biotechnology Information. PubChem Database. Pirfenidone, CID=40632, https://pubchem.ncbi.nlm.nih.gov/compound/Pirfenidone (accessed on Jan. 22, 2020)
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