Nefazodone is metabolized in the liver, with the main enzyme involved thought to be CYP3A4. The drug has at least four active metabolites, which include hydroxynefazodone, "para"-hydroxynefazodone, triazoledione, and "meta"-chlorophenylpiperazine. Nefazodone has a short elimination half-life of about 2 to 4 hours. Its metabolite hydroxynefazodone similarly has an elimination half-life of about 1.5 to 4 hours, whereas the elimination half-lives of triazoledione and mCPP are longer at around 18 hours and 4 to 8 hours, respectively. Due to its long elimination half-life, triazole is the major metabolite and predominates in the circulation during nefazodone treatment, with plasma levels that are 4 to 10 times higher than those of nefazodone itself. Conversely, hydroxynefazodone levels are about 40% of those of nefazodone at steady state. Plasma levels of mCPP are very low at about 7% of those of nefazodone; hence, mCPP is only a minor metabolite. mCPP is thought to be formed from nefazodone specifically by CYP2D6.