The CYP3A5 gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. The enzyme metabolizes drugs such as olanzapine, tacrolimus, nifedipine and cyclosporine as well as the steroid hormones testosterone, progesterone and androstenedione. Wikipedia This gene may be an important contributor to individual and inter-racial variation in CYP3A mediated metabolism of drugs including antipsychotics (olanzapine), antiestrogen (tamoxifen), anticancer (irinotecan, docetaxel, vincristine), antimalarial (mefloquine, artemether, lumefantrine), immunomodulators (tacrolimus, cyclosporine), antihistamines (chlorpheniramine, terfenadine, astemizole), antiplatelets (clopidogrel), antihypertensives (nifedipine, amlodipine, felodipine, verapamil), antivirals (indinavir, nelfinavir, ritonavir, saquinavir), HMG-CoA reductase inhibitors (atorvastatin, cerivastatin, lovastatin) antibiotics (clarithromycin) and steroids (testosterone, estradiol, progesterone and androstenedione). [PMID 24604039]
In terms of phenotypes, individuals are 'expressors' of CYP3A5 if they carry at least one CYP3A5*1 allele, and 'nonexpressors' if they don't have any.
Alleles of CYP3A5 include:
Note that CYP3A5 variant frequencies differ significantly by ethnicity; for example, most Caucasians are non-expressors, whereas many individuals of African descent are expressors for CYP3A5.
One study related to CYP3A5 SNPs was conducted among 200 postmenopausal females who had had a venous thromboembolism(VTE) episode and 500+ matched controls. As has been previously reported, oral estrogen increased VTE risk among all females (odds ratio of 4.5, CI: 2.6-7). Compared with nonusers, the odds ratio for VTE in users of oral estrogen was 3.8 (CI: 2.1-6.7) among patients lacking a CYP3A5*1 allele and 30.0 (CI = 4.4-202.9) among patients with this allele (test for interaction P = 0.04).[PMID 18628519]
A study of 64 Korean patients with schizophrenia under treatment with risperidone found higher plasma concentrations of the active moiety of the drug in CYP3A5 nonexpressors (8.39 ng/mL per milligram) than in expressors (5.30 ng/mL per milligram, P = 0.005).[PMID 19440082]
Promethease tests CYP3A5 status via gs155