Testosterone buciclate

The disadvantage of all esters described so far is that they produce initially supra-physiological testosterone levels which may exceed normal levels severalfold and then slowly decline, so that before the next injection pathologically low levels may be reached. Some patients recognize these ups and downs of testosterone levels in parallel variations of general well-being, sexual activity and emotional stability. Despite these disadvantages testosterone enanthate and cypionate are still the standard therapy for male hypogonadism.

Because of these shortcomings of the available esters the World Health Organization (WHO) initiated a steroid synthesis programme (Crabbe etal. 1980) out of which a series of new testosterone esters was developed. When tested in laboratory rodents a specific ester was identified that showed greatly prolonged activity, namely testosterone-trans-4-n-butylcyclohexyl-carboxylate, generic name testosterone buciclate. This preparation is injected intramuscularly in an aqueous solution, in contrast to the other testosterone esters which are dissolved in oily solution.

A first study on the pharmacokinetics of the new WHO/NIH androgen ester testosterone buciclate was performed in two groups of orchiectomized cynomol-gus monkeys (Weinbauer et al. 1986). Intramuscular injections of testosterone enanthate resulted in supraphysiological serum levels of testosterone for eight days, followed by a rapid decline with levels lower than the physiological limit after three weeks. In contrast, testosterone buciclate produced a moderate increase of serum testosterone levels into the physiological range, and serum levels remained in this range for a period of four months. These favourable results on the pharmacokinetics of testosterone buciclate were confirmed in castrated rhesus monkeys (Rajalakshmi and Ramakrishnan 1989).

To assess the pharmacokinetics of testosterone buciclate in men the first clinical study was performed in eight men with primary hypogonadism (Behre and Nieschlag 1992). The men were randomly assigned to two study groups and were given either 200 (group I) or 600 mg (group II) testosterone buciclate intramuscularly. Whereas in group I serum androgen levels did not rise to normal values, in group II androgens increased significantly and were maintained in the normal range up to 12 weeks with maximal serum levels (cmax) of 13.1 ± 0.9 nmol/l

Testosterone Buciclate Buy

Fig. 14.11 Single-dose pharmacokinetics of testosterone buciclate after intramuscular injection of 600 mg of the ester to four hypogonadal patients. Closed circles, mean ± SEM of testosterone serum concentrations actually measured; curve, best-fitted pharmacokinetic profile.

Fig. 14.11 Single-dose pharmacokinetics of testosterone buciclate after intramuscular injection of 600 mg of the ester to four hypogonadal patients. Closed circles, mean ± SEM of testosterone serum concentrations actually measured; curve, best-fitted pharmacokinetic profile.

(mean ± SEM) in study week 6 (tmax). No initial burst release of testosterone was observed in either study group. Pharmacokinetic analysis revealed a terminal elimination half-life of 29.5 ± 3.9 days (Fig. 14.11) (Table 14.2).

Because of the promising results of the first clinical study with testosterone buciclate, a follow-up study was initiated. After complete wash-out from previous therapy all hypogonadal men received a single intramuscular injection of 1000 mg testosterone buciclate. As in the previous study with lower doses, no initial burst release of testosterone was observed. Maximal testosterone serum levels were observed nine weeks (tmax) after injection with a mean value of 13.1 ± 1.8 nmol/l (cmax). Following peak concentrations, testosterone serum levels gradually declined and remained within the normal range up to week 16. This study demonstrated that an increase of the injected dose of testosterone buciclate from 600 to 1000 mg prolongs the duration of action significantly, but does not lead to significantly higher maximal serum levels of testosterone.

The long duration of action of testosterone buciclate was also demonstrated in a contraceptive study with this new testosterone ester. After a single intramuscular injection of 1200 mg testosterone buciclate at a concentration of 400 mg/ml to eight normal men, serum levels of testosterone remained within the normal range, whereas gonadotropins and spermatogenesis was significantly suppressed for at least 18 weeks (Behre etal. 1995). These studies demonstrate that the long-acting testosterone buciclate is well suited for substitution therapy of male hypogonadism as well as for male contraception. However, this compound has not been developed into a marketable product and is currently not available.

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