Like methandrostenolone (Dianabol), oxymetholone does not bind well to the androgen receptor (AR), and most of the anabolism it provides is via non-AR-mediated effects. It is therefore a Class II steroid and is best stacked with a Class I steroid. The drug appears to give the same benefits as dianabol. Unlike Dianabol, however, it seems that oxymetholone is progestagenic. It has been observed to cause nipple soreness or to aggravate gynecomastia even in the presence of high dose antiestrogens, strongly suggesting that the effect is not estrogenic. That effect can be reduced by concurrent use of stanozolol (Winstrol), which is anti-progestagenic. This progestagenic effect of oxymetholone is only a concern when using aromatizing steroids. With androgens such as Primobolan, oxymetholone stacks very nicely and is a surprisingly friendly drug. In contrast, with testosterone it is a very harsh drug. Oxymetholone does not convert to estrogen, and thus antiestrogens are not required if no aromatizable AAS are being used. However, in concert with aromatizing drugs, oxymetholone is notorious for worsening "estrogenic" symptoms, possibly by producing progestagenic symptoms which the bodybuilder confuses as estrogenic, or by altering estrogen metabolism, or by upregulating aromatase. Compared to what bodybuilders expect of it, the drug is reasonably mild when no aromatizing steroids are present. I consider its potency approximately comparable to Dianabol. It is not unusual for a first time user to do quite well on an oxymetholone-only cycle, but more advanced users will want to stack with another steroid. Typical use is 50-150 mg/day, which should be divided into several doses per day. Because oxymetholone is 17-alkylated, it is stressful to the liver. It is better to limit use to no more than 6 weeks or preferably four weeks before taking a break of at least equal length. Many users feel that it is more effectively used in the beginning parts of the cycle, rather than in the last few weeks. Trivial name Oxymetholone Systematic name 5-alpha,17-beta-Androstan-3-one, 17-hydroxy-2- (hydroxymethylene)-17-methyl- CAS number 434-07-1 ATC code A14AA05 Merck Index Number 7036 Chemical formula C21H32O3 Molecular weight 332.477 g/mol Bioavailability 95% Metabolism Hepatic Elimination half-life 9 hours Excretion Urinary: 95% Pregnancy category X Routes of administration Oral