Unlike methyltestosterone, owing to the presence of its C1(2) double bond, metandienone does not produce 5α-reduced metabolites. The drug is metabolized in the liver by 6β-hydroxylation, 3α- and 3β-oxidation, 5β-reduction, 17-epimerization, and conjugation among other reactions. It has very low affinity for human serum sex hormone-binding globulin (SHBG), about 10% of that of testosterone and 2% of that of DHT. The co-administration of an antiestrogen such as an aromatase inhibitor like anastrozole or a selective estrogen receptor modulator like tamoxifen can reduce or prevent such estrogenic side effects.
