14.3.6.3 Testosterone cypionate and testosterone cyclohexanecarboxylate
Testosterone cypionate (cyclopentylpropionate) pharmacokinetics were compared with those of testosterone enanthate in a cross-over study involving six healthy men aged 20***8211;29 years. Three subjects received 194 mg of testosterone enanthate, fol- lowed seven weeks later by 200 mg of testosterone cypionate and vice versa (amount of unesterified testosterone 140 mg in both preparations). The serum testosterone profiles were identical after injection of both preparations in equivalent doses, both in terms of maximal concentrations and in terms of duration of elevation above basal levels (Fig. 14.8) (Schulte-Beerbu ***776;hl and Nieschlag 1980).
In a subsequent clinical study the pharmacokinetics of testosterone cyclohex- anecarboxylate were compared to the pharmacokinetics of testosterone enanthate in a single-blind cross-over study in seven healthy young men (Schu ***776;rmeyer and Nieschlag 1984). After injection of either testosterone enanthate or testosterone cyclohexanecarboxylate, testosterone concentrations in serum increased sharply and reached maximum levels, 4***8211;5 times above basal, 8***8211;24 h after injection. During following days a parallel decay of testosterone levels occurred after injec- tion of either ester preparations, with testosterone serum concentrations slightly, but significantly lower after testosterone cyclohexanecarboxylate injection com- pared to testosterone enanthate injection two, three and seven days after admin- istration. Basal serum levels were reached seven days after testosterone cyclo- hexanecarboxylate administration and nine days after injection of testosterone enanthate.
Because testosterone cypionate, testosterone cyclohexanecarboxylate and testos- terone enanthate had comparable suppressing effects on LH and consequently on endogenous testosterone secretion, it can be concluded from these studies in normal volunteers that all three esters with similar molecular structure possess comparable pharmacokinetics of exogenous testosterone serum concentrations. Testosterone cypionate or testosterone cyclohexanecarboxylate do not provide a more advanta- geous pharmacokinetic profile than testosterone enanthate. This observation is in agreement with a clinical study of replacement therapy with single-dose admin- istration of 200 mg of testosterone cypionate in 11 hypogonadal patients (Nankin 1987).