Drug Interaction of Pirfenidone with Commonly Prescribed Pharmaceutical Drugs

Purpose Pirfenidone was initially developed as an antihelminthic, antipyretic agent now approved by US FDA as antifibrotic drug for the treatment of idiopathic pulmonary fibrosis. In vitro experiments with cell fractions from human liver and recombinant cytochrome P450 enzymes indicate that pirfenidone is primarily metabolized by CYP1A2, although multiple other CYP isoforms contribute to metabolism. Numbers of clinical drugs are substrates to these isoforms and thus it will have significant effects on pirfenidone metabolism. Thus in the present study, we sought to investigate effects of ethynyl estradiol, zileuton, itraconazole, diazepam, omeprazole and naproxen on pirfenidone metabolism using human liver microsomes. Methods We ordered human liver microsomes from Life Technologies, Grand Island, NY (Pooled human liver chromosome from 50 donors, CYP450 levels 0.286 nmol/mg; CYP1A2 activity V max 0.73 nmol/min/mg of protein, K m 78μM). Pirfenidone, ethynyl estradiol, itraconazole, zileuton, diazepam, omeprazole, naproxen, and DMSO were from Sigma Aldrich, St. Louis MO. Ethyl acetate and 100mM phosphate buffer were from VWR, Randor, PA, C18 (5μm × 4.6mm × 150mm) and guard column were from Waters, Milford, MA. Waters HPLC equipped with photodiode array detector was used for separation and quantification. All other reagents were of analytical and HPLC grade. Briefly the microsomes were incubated with or without drugs (DMSO) at 37°C for 1h in phosphate buffer (total reaction volume was 200uL). Reaction was initiated by adding 20mM NADPH and terminated with equal volume of ethyl acetate. The reaction tubes were vortexed for few seconds to mix all contents and then centrifuged at 7,000g for 10 minutes at 4°C. Supernatant was isolated and stored until further processing at −80°C. 20uL of samples were eluted on HPLC using acetonitrile:water (65:35) as mobile phase at the rate of 0.7 mL/min. Detection wavelength was 317nm. Standard curve was run with same condition using denatured human liver microsomes. Results Our microsomal incubation studies show that pirfenidone concentration was significantly increased (126%) when used together with omeprazole as compared to pirfenidone alone. No significant increase in pirfenidone concentration was noted with other drugs (estradiol, itraconazole, zileuton, or naproxen) when used together with pirfenidone. Conclusion Our study suggests that there is a potential drug interaction of pirfenidone with omeprazole when used simultaneously. Support or Funding Information Roseman University of Health Sciences