Nilutamide is a nitroaromatic hydantoin analog of flutamide, as seen in figure 5. Nilutamide is eliminated exclusively by metabolism, mainly by reduction of the aromatic nitro group. Although the hydrolysis of one of the carbonyl functions of the imidazolinedione was identified, it is much less susceptible to hepatic metabolism than the amide bond in hydroxuflutamide. This results in a longer half-life of nilutamide in humans of 2 days. Nevertheless, the nitro anion-free radical formed during nitro reduction could still be associated with hepatotoxicity in humans, especially when using relatively high dosage employed for androgen blockage. Nilutamide causes side-effects which limit its usage, such as pneumonitis and delayed adaption to darkness.