Am I confused about Enanthate being a faster acting ester than Cyp? Like in the middle between Prop and Cyp which I had a bad experience with (My daily Testosterone Propionate diary) Seems like I have it stuck in my head with Test-E being more about ~48hrs but I can't seem to find that info...
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COMPARISON OF TESTOSTERONE, DIHYDROTESTOSTERONE, LUTEINIZING HORMONE, AND FOLLICLE-STIMULATING HORMONE IN SERUM AFTER INJECTION OF TESTOSTERONE ENANTHATE OR TESTOSTERONE CYPIONATE
DISCUSSION
Injection of either testosterone enanthate or testosterone cypionate in equivalent doses yielded identical serum testosterone concentrations both in terms of maximal concentrations and in terms of duration of elevation above basal levels. Maximal and supraphysiologic levels were achieved as early as the 1st day after injection, and these values had returned to basal concentrations on day 10. There were also no differences in the conversion of testosterone to DHT and in the suppression of LH and FSH observed_
Thus, both esters show the same pharmacokinetic properties and appear to be equally useful for clinical purposes.
Pharmacology of testosterone preparations
H.M. Behre, C. Wang, D.J. Handelsman and E. Nieschlag
14.3.6.2 Testosterone enanthate
Single-dose pharmacokinetics of testosterone enanthate after intramuscular administration of 250 mg testosterone enanthate to seven hypogonadal patients and the best-fitted pharmacokinetic profile are shown in Fig. 14.6 (Nieschlag et al. 1976). Maximal testosterone levels in the supraphysiological range were seen shortly after injection (39.4 nmol/l, tmax = 10 h). Testosterone levels below the normal range were observed following day 12 after injection. The calculated values were 9911 nmol ∗ h/l for AUC, 8.5 d for MRT, and 4.5 d for terminal half-life (Table 14.2). Based on the pharmacokinetic parameters of single-dose pharmacokinetics multiple-dose pharmacokinetic simulations for equal doses of 250 mg testosterone enanthate and injection intervals of one to four weeks were performed.
With weekly injection intervals, supraphysiological maximal testosterone serum concentrations up to 78 nmol/l are observed at steady-state shortly after injection and supraphysiological minimal testosterone serum concentrations up to 40 nmol/l just before the next injection (Fig. 14.7). Injecting 250 mg of testosterone enanthate every two weeks results in maximal supraphysiological testosterone serum concentrations of up to 51 nmol/l shortly after injection and testosterone serum levels at the lower range for normal testosterone serum concentration shortly before the next injection. If the injection interval is extended to three weeks, testosterone serum concentrations below the normal range are observed 14 days after injection. With injection intervals of four weeks, testosterone serum concentrations are in the subnormal range at week three and four and effective testosterone substitution is not guaranteed (Fig. 14.7).
The calculated testosterone serum concentrations at steady state obtained by computer simulation correspond well to the results of published studies describing multiple-dose testosterone enanthate pharmacokinetics. In a clinical trial for male contraception, 20 healthy men were injected with 200 mg/wk of testosterone enanthate for 12 weeks (Cunningham et al. 1978). Minimal serum concentrations of testosterone at steady state, i.e. the testosterone serum concentration just before the next injection, were measured at 31.2 nmol/l to 39.5 nmol/l after weekly injections of 200 mg testosterone enanthate. Very similar data were obtained in further contraceptive studies when normal men received 200 mg/wk testosterone enanthate injections for 18 months (Anderson and Wu 1996; Wu et al. 1996). The data of these studies fit well with the computer-calculated minimal testosterone serum concentrations of 40 nmol/l and maximal testosterone levels 78 nmol/l after multiple injections of testosterone enanthate at a dosage of 250 mg/wk.
Snyder and Lawrence (1980) administered 100 mg/wk (n = 12), 200 mg/2 wks (n = 10), 300 mg/3 wks (n = 9) and 400 mg/4 wks (n = 6) testosterone enanthate to hypogonadal patients during a study period of three months. Blood was drawn during the last injection period when steady-state had been reached, every day (100 mg/wk) up to every fourth day (400 mg/4 wks).
Similar to the computer simulation described above for 250 mg testosterone enanthate and injections intervals of one to four weeks, initial supraphysiological testosterone serum levels were seen shortly after injection. In the 100 mg/wk treatment group, where daily blood sampling was performed, mean peak serum concentrations were seen 24 h after injection. Comparable to the results of the computer simulation, after injection of 200 mg/2 wks testosterone enanthate, following initial supraphysiological testosterone serum levels, values fell to progressively lower values before the next injection, eventually reaching the lower normal limit (Snyder and Lawrence 1980). Similar results were described after injection of 300 mg/3 wks or 400 mg/4 wks testosterone enanthate. The authors conclude that the testosterone enanthate doses of 200 mg have to be injected every two weeks or doses of 300 mg every 3 weeks to guarantee effective substitution therapy.
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 20–29 years.
Three subjects received 194 mg of testosterone enanthate, followed 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-Beerbuhl and Nieschlag 1980). In a subsequent clinical study, the pharmacokinetics of testosterone cyclohexanecarboxylate were compared to the pharmacokinetics of testosterone enanthate in a single-blind cross-over study in seven healthy young men (Schurmeyer and Nieschlag 1984). After injection of either testosterone enanthate or testosterone cyclohexanecarboxylate, testosterone concentrations in serum increased sharply and reached maximum levels, 4–5 times above basal, 8–24 h after injection. During the following days a parallel decay of testosterone levels occurred after injection of either ester preparations, with testosterone serum concentrations slightly, but significantly lower after testosterone cyclohexane carboxylate injection compared to testosterone enanthate injection two, three and seven days after administration. Basal serum levels were reached seven days after testosterone cyclohexanecarboxylate administration and nine days after injection of testosterone enanthate
Because testosterone cypionate, testosterone cyclohexanecarboxylate, and testosterone 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 advantageous pharmacokinetic profile than testosterone enanthate. This observation is in agreement with a clinical study of replacement therapy with single-dose administration of 200 mg of testosterone cypionate in 11 hypogonadal patients (Nankin 1987).
*Keep in mind with the above studies except for one of them by Nieschlag that blood work was not taken hourly post-injection let alone prior to 24 hrs!
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