Testosterone enanthate is a slow-acting injectable form of the androgen testosterone. Following deep intramuscular injection, the drug is designed to provide a sustained release of testosterone into the bloodstream for approximately 2 to 3 weeks. In order to maintain normal physiological levels of testosterone during androgen replacement therapies, injections of testosterone enanthate are usually required at least every two weeks, although more meticulous physicians will administer the drug weekly. As with all testosterone injectables, testosterone enanthate is highly favored by athletes for its ability to promote strong increases in muscle mass and strength.
Testosterone enanthate first appeared on Western drug markets during the early 1950s. It was the first slow-acting oil-based injectable ester of testosterone to be widely adopted in Western medicine, and effectively replaced testosterone propionate and testosterone suspension for most therapeutic uses. The first brand of this drug to be sold in the U.S. was Delatestryl® by Squibb. Over the years the Delatestryl® brand has changed hands several times, most notably to Mead Johnson, BTG, Savient, and in December 2005, Indevus. The most prominent brand of testosterone enanthate outside of the United States is Testoviron®, a drug that has seen uninterrupted production by the same manufacturer (Schering AG, Germany) for more than 50 years. Globally, the Testoviron® brand from Schering is the single most widely used injectable testosterone preparation.
Testosterone enanthate is most often used clinically to replace normal levels of testosterone in Adult males suffering diminished androgen levels. This may manifest itself with a loss of libido, lean muscle mass, and normal energy and vigor. Testosterone enanthate is also used to treat undescended testicles and delayed puberty in adolescent males, and occasionally as a secondary medication during inoperable breast cancer in women. This form of testosterone has also been studied with great success as a male birth control option.1 Weekly injections of 200 mg were shown to efficiently lower sperm production for most men within three months of treatment, a state of suppression that remained until after the drug was discontinued. With the current stigma surrounding anabolic/androgenic steroids, however, it is unlikely that such therapy will become adopted in Western medical practice. Today, in spite of the growing number of alternative therapies, testosterone enanthate remains the most widely prescribed form of testosterone in the world.
Testosterone enanthate is widely available in human and veterinary drug markets. Composition and dosage may vary by country and manufacturer, but usually contain 50 mg/ml, 100 mg/ml, 200 mg/ml, or 250 mg/ml of steroid dissolved in oil.
Testosterone enanthate is a modified form of testosterone, where a carboxylic acid ester (enanthate acid) has been attached to the 17-beta hydroxyl group. Esterified forms of testosterone are less polar than free testosterone and are absorbed more slowly from the area of injection. Once in the bloodstream, the ester is removed to yield free (active) testosterone. Esterified forms of testosterone are designed to prolong the window of therapeutic effect following administration, allowing for a less frequent injection schedule compared to injections of free (unesterified) steroid. The half-life of testosterone enanthate is approximately eight days after injection.
Side Effects (Estrogenic)
Testosterone is readily aromatized in the body to estradiol (estrogen). The aromatase (estrogen synthetase) enzyme is responsible for this metabolism of testosterone. Elevated estrogen levels can cause side effects such as increased water retention, body fat gain, and gynecomastia. Testosterone is considered a moderately estrogenic steroid. An anti-estrogen such as clomiphene citrate or tamoxifen citrate may be necessary to prevent estrogenic side effects. One may alternately use an aromatase inhibitor like Arimidex® (anastrozole), which more efficiently controls estrogen by preventing its synthesis. Aromatase inhibitors can be quite expensive in comparison to anti-estrogens, however, and may also have negative effects on blood lipids.
Estrogenic side effects will occur in a dose-dependent manner, with higher doses (above normal therapeutic levels) of testosterone more likely to require the concurrent use of an anti-estrogen or aromatase inhibitor. Since water retention and loss of muscle definition are common with higher doses of testosterone, this drug is usually considered a poor choice for dieting or cutting phases of training. Its moderate estrogenicity makes it more ideal for bulking phases, where the added water retention will support raw strength and muscle size, and help foster a stronger anabolic environment.
Side Effects (Androgenic)
Testosterone is the primary male androgen, responsible for maintaining secondary male sexual characteristics. Elevated levels of testosterone are likely to produce androgenic side effects including oily skin, acne, and body/facial hair growth. Men with a genetic predisposition for hair loss (androgenetic alopecia) may notice accelerated male pattern balding. Those concerned about hair loss may find a more comfortable option in nandrolone decanoate, which is a comparably less androgenic steroid. Women are warned of the potential virilizing effects of anabolic/androgenic steroids, especially with a strong androgen such as testosterone. These may include deepening of the voice, menstrual irregularities, changes in skin texture, facial hair growth, and clitoral enlargement.
In androgen-responsive target tissues such as the skin, scalp, and prostate, the high relative androgenicity of testosterone is dependant on its reduction to dihydrotestosterone (DHT). The 5-alpha reductase enzyme is responsible for this metabolism of testosterone. The concurrent use of a 5-alpha reductase inhibitor such as finasteride or dutasteride will interfere with site-specific potentiation of testosterone action, lowering the tendency of testosterone drugs to produce androgenic side effects. It is important to remember that anabolic and androgenic effects are both mediated via the cytosolic androgen receptor. Complete separation of testosterone’s anabolic and androgenic properties is not possible, even with total 5-alpha reductase inhibition.
Side Effects (Hepatotoxicity)
Testosterone does not have hepatotoxic effects; liver toxicity is unlikely. One study examined the potential for hepatotoxicity with high doses of testosterone by administering 400 mg of the hormone per day (2,800 mg per week) to a group of male subjects. The steroid was taken orally so that higher peak concentrations would be reached in hepatic tissues compared to intramuscular injections. The hormone was given daily for 20 days and produced no significant changes in liver enzyme values including serum albumin, bilirubin, alanine-amino-transferase, and alkaline phosphatases.
Side Effects (Cardiovascular)
Anabolic/androgenic steroids can have deleterious effects on serum cholesterol. This includes a tendency to reduce HDL (good) cholesterol values and increase LDL (bad) cholesterol values, which may shift the HDL to LDL balance in a direction that favors greater risk of arteriosclerosis. The relative impact of an anabolic/androgenic steroid on serum lipids is dependant on the dose, route of administration (oral vs. injectable), type of steroid (aromatizable or non-aromatizable), and level of resistance to hepatic metabolism. Anabolic/androgenic steroids may also adversely effect blood pressure and triglycerides, reduce endothelial relaxation, and support left ventricular hypertrophy, all potentially increasing the risk of cardiovascular disease and myocardial infarction.
Testosterone tends to have a much less dramatic impact on cardiovascular risk factors than synthetic steroids. This is due in part to its openness to metabolism by the liver, which allows it to have less effect on the hepatic management of cholesterol. The aromatization of testosterone to estradiol also helps to mitigate the negative effects of androgens on serum lipids. In one study, 280 mg per week of testosterone ester (enanthate) had a slight but not statistically significant effect on HDL cholesterol after 12 weeks, but when taken with an aromatase inhibitor a strong (25%) decrease was seen. Studies using 300 mg of testosterone ester (enanthate) per week for 20 weeks without an aromatase inhibitor demonstrated only a 13% decrease in HDL cholesterol, while at 600 mg the reduction reached 21%. The negative impact of aromatase inhibition should be taken into consideration before such a drug is added to testosterone therapy.
Due to the positive influence of estrogen on serum lipids, tamoxifen citrate or clomiphene citrate are preferred to aromatase inhibitors for those concerned with cardiovascular health, as they offer a partial estrogenic effect in the liver. This allows them to potentially improve lipid profiles and offset some of the negative effects of androgens. With doses of 600 mg or less per week, the impact on lipid profile tends to be noticeable but not dramatic, making an anti-estrogen (for cardioprotective purposes) perhaps unnecessary. Doses of 600 mg or less per week have also failed to produce statistically significant changes in LDL/VLDL cholesterol, triglycerides, apolipoprotein B/C-III, C-reactive protein, and insulin sensitivity, all indicating a relatively weak impact on cardiovascular risk factors. When used in moderate doses, injectable testosterone esters are usually considered to be the safest of all anabolic/androgenic steroids.
To help reduce cardiovascular strain it is advised to maintain an active cardiovascular exercise program and minimize the intake of saturated fats, cholesterol, and simple carbohydrates at all times during active AAS administration. Supplementing with fish oils (4 grams per day) and a natural cholesterol/antioxidant formula such as Lipid Stabil or a product with comparable ingredients is also recommended.
Side Effects (Testosterone Suppression)
All anabolic/androgenic steroids, when taken in doses sufficient to promote muscle gain, are expected to suppress endogenous testosterone production. Testosterone is the primary male androgen and offers strong negative feedback on endogenous testosterone production. Testosterone-based drugs will, likewise, have a strong effect on the hypothalamic regulation of natural steroid hormones. Without the intervention of testosterone-stimulating substances, testosterone levels should return to normal within 1-4 months of drug secession. Note that prolonged hypogonadotrophic hypogonadism can develop secondary to steroid abuse, necessitating medical intervention.
As with all anabolic/androgenic steroids, it is unlikely that one will retain every pound of new bodyweight after a cycle is concluded. This is especially true when withdrawing from a strong (aromatizing) androgen like testosterone, as much of the new weight gain is likely to be in the form of water retention; quickly eliminated after drug discontinuance. An imbalance of anabolic and catabolic hormones during the post-cycle recovery period may further create an environment that is unfavorable for the retention of muscle tissue. Proper ancillary drug therapy is usually recommended to help restore hormonal balance more quickly, ultimately helping the user retain more muscle tissue.
To treat androgen insufficiency, the prescribing guidelines for testosterone enanthate call for a dosage of 50-400 mg every 2 to 4 weeks. Although active in the body for a longer time, testosterone enanthate is usually injected on a weekly basis for muscle-building purposes. The usual dosage for physique- or performance-enhancing purposes is in the range of 200-600 mg per week, taken in cycles 6 to 12 weeks in length. This level is sufficient for most users to notice exceptional gains in muscle size and strength.
Testosterone is usually incorporated into bulking phases of training when added water retention will be of little consequence, the user more concerned with raw mass than definition. Some do incorporate the drug into cutting cycles as well, but typically in lower doses (100- 200 mg per week) and/or when accompanied by an aromatase inhibitor to keep estrogen levels under control. Testosterone enanthate is a very effective anabolic drug and is often used alone with great benefit. Some, however, find a need to stack it with other anabolic/androgenic steroids for a stronger effect, in which case an additional 200-400 mg per week of boldenone undecylenate, methenolone enanthate, or nandrolone decanoate should provide substantial results with no significant hepatotoxicity. Testosterone is ultimately very versatile and can be combined with many other anabolic/androgenic steroids to tailor the desired effect.
Testosterone enanthate is rarely used with women in clinical medicine. When applied, it is most often used as a secondary medication during inoperable breast cancer, when other therapies have failed to produce a desirable effect and suppression of ovarian function is necessary. Testosterone enanthate is not recommended for women for physique- or performance-enhancing purposes due to its strong androgenic nature, tendency to produce virilizing side effects, and slow-acting characteristics (making blood levels difficult to control).
Testosterone enanthate remains the most widely manufactured form of injectable testosterone worldwide and is produced in many generic and brand name forms.