Testosterone implants

It has been claimed that testosterone implants are much less likely to cause acne than are injections of testosterone enanthate in equivalent doses it is not clear why this might be expected and the claim seems dubious. 

Testosterone is available as oral testosterone undecano-ate, buccal testosterone, intramuscular testosterone esters, testosterone implants, and testosterone transdermal patches and gel. Proponents of transdermal testosterone products, such as gels and scrotal or non-scrotal dermal patches, claim that they have a good safety profile (101). Transdermal testosterone replacement certainly improves bone mass and lean body mass, reduces fat mass, and improves mood and sexual function. There are said to be no harmful effects on the prostate and lipids. Acne, polycythemia, and gynecomastia are stated to be less common with this form of therapy than with the intramuscular esters. To date these claims must be regarded with some reservations it is not at all clear that in equieffective doses the local or topical forms of administration dissociate wanted and unwanted effects. 

Testosterone implants, like implants of other substances, can be subject to extrusion, probably in about a tenth of cases treated, and can also give rise to local irritation (116). 

Handelsman DJ, Mackey MA, Howe C, Turner L, Conway AJ. An analysis of testosterone implants for androgen replacement therapy. Clin Endocrinol (Oxf) 1997 47(3) 311-6. 

Testosterone implants Testopel pellets Androgen deficiency delayed puberty in boys Subcutaneous... 

Figure 9.4 Immunoreactivity of liver microsomes from sexually intact control, sham control, gonadectomized mice, or mice undergoing gonadectomy and/or receiving testosterone implants (5 mg). (From J. G. Falls et al., Arch. Biochem. Biophys. 342 212-223, 1997.)...

Testosterone is available as oral testosterone undecano-ate, buccal testosterone, intramuscular testosterone esters, testosterone implants, and testosterone transder-mal patches and gel. 

Testosterone is available as oralmethyltestosterone in the United States and as testosterone implants in the United Kingdom. Of the available oral preparations, methyltestosterone in combination with esterifled estrogen (either 0.625 mg esterifled estrogen plus 1.25 mg methyltestosterone or 1.25 mg esterifled estrogen plus 2.5 mg methyl-testosterone) is the most widely studied. 

Drug administration route Published experience with testosterone pellets of an older type has noted relatively high rates of pellet extrusion (8.5-12%) and infection (1.4-6.8%). A study in 80 men with long-acting testosterone implants (Testopel ), which are smaller and have a smooth surface, has shown that with this formulation extrusion occurred in only 0.3% of cases and infection also in only 0.3% [105 ]. 

Implants are small, sterile cylinders of dmg, inserted beneath the skin or into muscle hssue to provide slow absorption and prolonged achon therapy. This is principally based on the fact that such dmgs, invariably hormones, are almost insoluble in water and yet the implant provides a rate of dissoluhon sufficient for a therapeuhc effect. The British Pharmacopoeia (1993) describes one implant, testosterone. The United States National Formulary (1990) also ineludes oestradiol. Implants are made fiom the pure drug into tablet form by compression or fusion. No other ingredient can be included sinee this may be insoluble or toxie or, most importantly, may influence the rate of drug release. 

Subcutaneous implant Testosterone (Testopel) 75-mg pellet 150-450 mg every 3-4 months... 

Hormone implants can be used for long-term stimulation or suppression of odor production. Scent marking is stimulated by testosterone in gerbils and wolves (Asa etal., 1990). 

Males also depend on testosterone for olfactory performance. If in hamsters testosterone is converted to estrogen by subcutaneous silastic implants of the aromatase inhibitor l,4,6-androstatriene-3,17-dione, their sexual sniffing decreases. They sniff less toward novel females and no longer discriminate between males and females (Steel and Hutchinson, 1987). Castration affects odor detection performance in male rats (Doty and Ferguson-Segall 1989). 

Determination of dose-The number of pellets to be implanted depends upon the minimal daily requirement of testosterone propionate determined by a gradual reduction of the amount administered parenterally. The usual ratio is as follows Implant two 75 mg pellets for each 25 mg testosterone propionate required weekly. It has been found that approximately 33% of the material is absorbed in the first month, 25% in the second month, and 17% in the third month. Adequate effect of the pellets ordinarily continues for 3 to 4 months, sometimes as long as 6 months. 

Mesterolone is a non-17-alkylated derivative which is also has weak activity orally. Testosterone itself has little activity when taken orally and is used sublingually or as an implant. By esterification of testosterone formulations of long-acting testosterone derivatives in oily solutions for intramuscular injection were developed. 

GnRH analogues (see Chapter 59) can induce chemical castration by suppressing the pulsatile release of LH and FSH, hence inhibiting testicular steroidogenesis. Administration of these compounds reduces circulating testosterone levels. These compounds are inhaled, injected subcutaneously, or implanted subcutaneously. They are used in males in the treatment of precocious puberty and carcinoma of the prostate. 

Christensen, L.W, and Clemens, L.G. (1974) Intrahypothalamic implants of testosterone or estradiol and resumption of masculine sexual behavior in long-term castrated male rats. Endocrinology 95 984-990. 

The other related subcutaneous routes are dermojet (by which, drug is projected from a microfine orifice using a high velocity jet) and pellet implantation (which provides sustained release of the drug over weeks and months e.g. testosterone). 

Testosterone is used for growth-promoting purposes in cattle as an subcutaneous implant in the ear, in combination with estradiol or its esters. It is usually administered in the form of its acetate, propionate, or isobutyrate esters. 

These preparations are used in states of infertility to stimulate ovarian follicle development in women and spermatogenesis in men. In both sexes, they must be used in conjunction with a luteinizing hormone, ie, human chorionic gonadotropin (hCG), to permit ovulation and implantation in women and testosterone production and full masculinization in men. 

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