The FDA has approved two new oral formulations of testosterone undecanoate — Kyzatrex (Marius) and Tlando (Antares) — for treatment of males with a deficiency of endogenous testosterone due to conditions such as Klinefelter syndrome, orchiectomy, toxic damage from chemotherapy or alcohol, or pituitary-hypothalamic injury caused by tumors, trauma, or radiation. Jatenzo, another oral testosterone undecanoate formulation, was approved for the same indication in 2019. No testosterone products are approved for treatment of low testosterone levels due solely to aging.

The FDA has approved an auto-injector formulation of testosterone enanthate (Xyosted – Antares Pharma) for once-weekly subcutaneous self-administration in adult males with conditions associated with a deficiency or absence of endogenous testosterone. It is the first subcutaneous formulation of testosterone to be approved by the FDA. Xyosted is contraindicated for treatment of low testosterone levels associated with aging.

Three coordinated double-blind, placebo-controlled clinical trials have evaluated the efficacy of one year of testosterone replacement therapy in improving sexual function, physical function, and vitality in a total of 790 men ≥65 years old with moderately low serum testosterone concentrations and symptoms suggesting hypoandrogenism. Sexual function improved modestly, and there appeared to be marginal benefits in some areas of physical function and vitality as well. The trials were not designed to evaluate the safety of testosterone replacement therapy.

The FDA has approved an intranasal gel formulation of testosterone (Natesto – Trimel/Endo) for replacement therapy in men with hypogonadism. Packaged in a metered-dose pump, Natesto is the first intranasal testosterone to become available in the US. Like other testosterone products, it is classified as a schedule III controlled substance. The FDA recently cautioned against using testosterone to treat low testosterone levels solely due to aging because the benefits and safety of such use have not been established, and there is a possible increased risk of myocardial infarction (MI) and stroke.

The FDA has approved testosterone undecanoate (Aveed – Endo), an injectable depot formulation, for use in men with hypogonadism who require testosterone replacement therapy.

Prompted by the recent publication of 2 retrospective studies, the FDA has announced that it is investigating the risk of stroke, heart attack, and death in men taking FDA-approved testosterone products.1

The first study examined the records of 8709 men with low testosterone levels (<300 ng/dL) who underwent coronary angiography between 2005 and 2011; 1223 of these men started testosterone therapy after a median of 531 days following coronary angiography. Three years after coronary angiography, the Kaplan-Meier estimated cumulative percentages of men who died or had a myocardial infarction (MI) or ischemic stroke were 26% of those treated with testosterone and 20% of those who were not treated with the hormone, a hazard ratio of 1.29 (95% CI 1.04-1.58; P=0.02).2

The second study compared the rate of nonfatal MI during the 90 days after filling a prescription with the rate in the prior year in 56,000 men given a prescription for testosterone and in 167,000 given a phosphodiesterase type 5 inhibitor (sildenafil [Viagra] or tadalafil [Cialis]). In the testosterone group as a whole, the post/pre-prescription rate ratio was 1.36, but in men ≥65 years old it was 2.19 and in younger men with a history of heart disease it was 2.90. In men who received a prescription for sildenafil or tadalafil, the rate ratio was 1.08 for all ages, 1.15 for those ≥65 years old, and 1.40 for younger men with a history of heart disease.3

A recent meta-analysis of randomized, placebo-controlled trials of testosterone therapy also found an increased risk of cardiovascular-related events in men treated with the hormone (odds ratio [OR] 1.54; 95% CI 1.09-2.18); an analysis by funding source found that the risk was greater in trials not funded by the pharmaceutical industry (OR 2.06 vs. 0.89).4

1. FDA Drug Safety Communication January 31, 2014: FDA evaluating risk of stroke, heart attack and death with FDA-approved testosterone products. Available at www.fda.gov. Accessed February 24, 2014.

2. R Vigen et al. Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. JAMA 2013; 310:1829.

3. WD Finkle et al. Increased risk of non-fatal myocardial infarction following testosterone therapy prescription in men. PLoS One 2014; 9:e85805.

4. L Xu et al. Testosterone therapy and cardiovascular events among men: a systematic review and meta-analysis of placebo-controlled randomized trials. BMC Med 2013; 11:108.

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The Medical Letter recently reviewed a topical gel formulation of testosterone (Fortesta) for treatment of hypogonadism in men. A topical testosterone replacement product for application to the axilla, Axiron (Lilly) solution, has now become available for the same indication. This site of application presumably minimizes the risk of transferring the drug to a family member or sexual partner.

The FDA has approved Fortesta (Endo), a topical gel, for testosterone replacement therapy in adult males with hypogonadism. It is classified as a Schedule III controlled substance. Table 1 lists some available testosterone products, including 2 other gels.

Sexual complaints related to desire, arousal, orgasm and painful intercourse are common in women. Since the last Medical Letter article on this subject, some new information has become available.

In recent years, many women have become concerned about the safety of pharmaceutical replacement hormones for treatment of menopausal symptoms. “Bioidentical” hormone preparations, which are not approved by the FDA, are heavily promoted in popular books and on TV as alternatives; these are derivatives of soy or plant extracts, chemically modified to be structurally identical to endogenous hormones. Most FDA-approved single-entity hormones are also derivatives of soy or plant extracts and are structurally identical to hormones produced by the ovary.

The FDA has approved degarelix (Firmagon - Ferring), a synthetic decapeptide gonadotropin-releasing hormone (GnRH) receptor antagonist, for rapid medical castration of men with advanced prostate cancer. Abarelix (Plenaxis), the first GnRH antagonist approved by the FDA, was withdrawn from the US market because of immediate hypersensitivity reactions.

Patients are asking physicians about an article on the front page of the June 15th New York Times, in which some prostate cancer experts were quoted as suggesting that men 55 and older might be well advised to take finasteride (Proscar, and others) to prevent prostate cancer.

Sexual complaints related to desire, arousal, orgasm and pain are common in women. No drugs are approved by the FDA for any of these indications, but many are used off-label.

With the 2004 Olympics only weeks away, performance-enhancing drugs will once again be receiving a great deal of attention. The US Anti-Doping Agency has published a list of drugs banned in Olympic sports (www.usantidoping.org) that includes, at least for some sports, all but 2 of the drugs reviewed here.

Two new topical testosterone products, a 1% gel (Testim) and a buccal tablet (Striant), have been approved by the FDA for treatment of hypogonadism in men. This review briefly describes hypogonadism and its causes and lists other available formulations of testosterone. For the new products, information on pharmocokinetics, adverse effects, and dosage and administration is provided, as well as a summary of clinical trial results. A dosage and cost table for topical testosterone products is also included. The conclusion summarizes the safety and effectiveness of the new drugs and discusses the potential risks and benefits of using testosterone replacement therapy in older men.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.

Reports of adverse interactions between drugs continue to accumulate. Recently, the FDA has expanded the recommendations on drug interactions found in the package inserts of new drugs.