Purity >95%. Furafylline is a selective inhibitor of human cytochrome P450 (CYP)1A2 (IC50 = 0.07 μM), demonstrating little effect on other CYP isoforms including 2D1, 2C, 3A, or 1A1. It was originally introduced as a bronchodilator with extended duration compared to theophylline, but then subsequently reported to inhibit the oxidation of caffeine , a reaction catalyzed by CYP1A2.