Anabolic agent

The application of the Birch reduction to ethers of estradiol by A. J. Birch opened up the area of 19-norsteroids to intensive research. The major Birch reduction product is an enol ether which affords either a 3-keto-A -or a 3-keto-A -19-norsteroid depending upon the hydrolysis conditions. Various 19-norsteroids have been found to have useful clinical activity compounds (30), (31), and (32) are oral contraceptive agents and compound (33) has been used as an oral anabolic agent. Several of these compounds were prepared on an industrial scale for a number of years by the Birch reduction of estradiol derivatives. 

B-Homosteroids were first reported by Ringold in the course of an investigation of the relationship of structural changes to biological activity of anabolic agents. The Tiffeneau rearrangement sequence described earlier for the preparation of A-homosteroids was used to synthesize 17/ -hydroxy-B-homo-5a-androstan-3-one (56a). 

Teriparatide, recombinant human parathyroid hormone) 1-34), is the first anabolic agent approved by the FDA for treatment of... 

The mechanism of this effect was addressed in a study in which 2-5 days treatment of female cynomolgus monkeys with relacatib transiently caused a 2-3-fold increase in plasma levels of parathyroid hormone (PTH, a bone anabolic agent) post-dosing compared to vehicle-treated animals [24]. 

Anabolic Agents—includes anabolic androgenic steroids such as stanozolol and other... 

Androgens and anabolic agents have been used in the treatment of osteoporosis, either alone or in conjunction with estrogens. With the exception of substitution therapy in hypogonadism, bisphosphonates have largely replaced androgen use for this purpose. 

Most of the synthetic androgens and anabolic agents are 17-alkyl-substituted steroids. Administration of drugs with this structure is often associated with evidence of hepatic dysfunction. Hepatic dysfunction usually occurs early in the course of treatment, and the degree is proportionate to the dose. Bilirubin levels may increase until clinical jaundice is apparent. The cholestatic jaundice is reversible upon cessation of therapy, and permanent changes do not occur. In older males, prostatic hyperplasia may develop, causing urinary retention. 

For all these hormonal substances to exert their desired effect, the method of administration to the animal is most important. They can be administered to animals by intramuscular injections but some compounds can be also administered incorporated into the feeds. However, the best method is one in which they are administered in form of a subcutaneous implant in the ear. This allows for a controlled slow release of the active ingredients, exposing the animal to a constant stimulating effect of the anabolic agent. 

The overall rate of absorption of an anabolic agent from an implant can be influenced by a number of factors, including the technique of administration, total dosage given, integrity of the implant, presence of a second anabolic in the implant, implant size, shape, and hardness. Since at the end of the withdrawal period, up to 10% of the initial dose may still be found at the site of implantation, care should always be taken to discard this area at slaughter. 

Estradiol-17 is given to animals in form of a subcutaneous implant in the ear, alone or in combination with other hormonally active compounds such as progesterone or trenbolone acetate. Estradiol-17 is used in steers, to best advantage, but also exhibits some anabolic effects in heifers and veal calves. It works best in lambs in conjunction with androgens, but is not effective as an anabolic agent in pigs. It has been used in many forms in the past including the benzoate, dipropionate, hemisuccinate, heptanoate, propionate, undecanoate, and valerate esters. 

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