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IM injections of long-acting testosterone esters (cypionate or enanthate) are cost-effective and result in physiological and predictable on-treatment serum testosterone levels, particularly when smaller doses are administered weekly (18). Major testosterone esters include testosterone cypionate, testosterone enanthate, testosterone propionate, and testosterone undecanoate. To date, limited data suggest that SC administration of testosterone enanthate and cypionate results in stable and predictable on-treatment concentrations, has good acceptability among patients, and can be self-administered more easily than IM injections.
The term ester is often used in the language of testosterone replacement therapy. You've come to our clinic after hearing about the benefits of testosterone replacement therapy (TRT), and you'd like to learn more before trying the treatment. Similar to IM injections, periodic monitoring of the patients for risks and benefits should continue as recommended by clinical practice guidelines (1). Patients should be informed that currently, data and experience with SC testosterone therapy both are limited. Once a patient qualifies for testosterone therapy (1, 2), risks and benefits of therapy as well as pros and cons of each formulation should be discussed (see Table 1).
For testosterone esters, the time corresponding from administration to the Cmax, that is, time of maximum concentration (tmax), is determined by the rate at which absorption occurs, since the systemic elimination of testosterone is the same regardless of the route of administration. B, Schematic illustration of the absorption steps of testosterone esters after intramuscular (left) or subcutaneous (right) injection. Owing to the convenience of self-administration of testosterone esters, the SC route has recently gained popularity. More recently, newer formulations of testosterone replacement have become available, which include ultralong-acting testosterone undecanoate for IM injection, transdermal patches and gels, buccal tablets, intranasal sprays, and oral testosterone undecanoate (Table 1), thus providing a range of options to choose from.
Furthermore, testosterone is one the oldest medications and has been demonstrated to be safe for clinical use. Testosterone is the most important androgenic and anabolic hormone in men. And suppression was greater with the long estered nandrolone deconate (deca-durabolin), and the anabolic effect was greater with the long ester (deca).
Aside from differences in pharmacokinetics (e.g., duration), these esters essentially have the same effects as the parent drugs. In addition, with intramuscular injection, AAS esters are absorbed more slowly into the body, thus further improving the elimination half-life. The choice between short and long esters depends on several factors, including your goals, experience level, and willingness to inject frequently. The longer the ester, the slower the release and the less frequent the injections needed.
On release from the depot, the testosterone ester undergoes hydrolysis into testosterone and the ester-specific fatty acid (35, 36). Benzyl alcohol is soluble not only in the oily phase, but also in the aqueous phase, thus facilitating the release of testosterone ester from the depot into the surrounding interstitial fluid (35). These oily solutions contain a testosterone ester dissolved in vegetable oil (usually sesame seed, tea seed, castor seed, or cottonseed oil) with some benzyl alcohol. Indeed, this might explain the observation that IM injections are less painful in overweight and obese men (34). Interestingly, previous data that used imaging (computed tomography or ultrasound) to estimate SC fat thickness and compared it with the length of the needle (or placement of the injectate) estimated that 12% to 85% of IM injections administered to men were actually SC (31-33). The viability of using SC route for sex steroid administration was also shown in an elegant pharmacokinetic study in which nandrolone decanoate was administered to healthy male volunteers (30). However, this device is expensive compared to administration of ester with conventional syringe and needles.
Testosterone deficiency (also termed hypotestosteronism or hypotestosteronemia) is an abnormally low testosterone production. Testosterone treatment for reasons other than possible improvement of sexual dysfunction may not be recommended. Decline of testosterone production with age has led to interest in testosterone supplementation. Serious side effects may include liver toxicity, heart disease, and behavioral changes. Thus, it takes longer for the full dose to fully circulate throughout the bloodstream.Testosterone is testosterone, regardless of the label.