May 13, 2015
Intramuscular Testosterone May Be Safer Than Other
Delivery Modes

Gainesville, FL—Here’s some interesting information to share with patients who come into the pharmacy to fill often expensive prescriptions for oral or transdermal testosterone replacement therapy: Receiving an intramuscular shot may be more effective and less risky.

That’s according to a study published early by the American Journal of Physiology.

Authors from the University of Florida and the Veterans’ Affairs Medical Center, both in Gainesville, report that while testosterone prescriptions have tripled in the United States in the last decade, debate continues over the risks and benefits of testosterone replacement therapy (TRT).

The treatment currently is prescribed for older men with either low serum testosterone (T) or low T plus accompanying symptoms of hypogonadism, although the authors point out, “Treatment for men who have low T without accompanying symptoms remains somewhat controversial.”

Background information in the articles notes that TRT produces benefits, including increased muscle mass and strength, decreased fat mass, and increased bone mineral density, but also raises the risk of known side effects such as polycythemia, decrease in HDL cholesterol levels, breast tenderness and enlargement, prostate enlargement, and increases in serum PSA and prostate-related events.

The authors point out that several recent reports have also indicated that TRT may produce cardiovascular (CV) risks, while others report no risk or even benefit.

To address the potential CV risks, the authors conducted a meta-analysis that suggests that intramuscular (i.m.) injections may be safer that either oral or transdermal preparations for older, hypogonadal men.

“First, the musculoskeletal benefits are greater, due to the higher doses administered i.m. vs transdermally,” the researchers write. “Second, although the doses are higher, i.m. TRT may not pose the same CV risks that result from transdermal TRT. A possible explanation for the latter phenomenon is that transdermal T causes greater elevation of serum DHT, due to significant expression of 5?-reductase in skin, but not in muscle.”

The researchers caution, however, that meta-analysis of existing randomized placebo-controlled trial “is, to date, insufficient to definitively assess the CV effects of TRT. However, existing data exhibit trends indicting 1) that TRT may not accelerate underlying early-stage prostate cancer 2) that transdermal TRT may cause CV risk and 3) that i.m. injected TRT may cause CV benefit.”

The study also notes that previous research has demonstrated that, in older hypogonadal men, the combination of i.m. testosterone plus finasteride produces musculoskeletal benefits without the prostate enlargement that results from testosterone alone, while also lowering dihydrotestosterone, a more potent androgen.

“Finasteride produces relatively few adverse events and may also produce cardiovascular benefits and/or reduce prostate cancer by reducing DHT,” the authors conclude. “While further research is needed, it appears at this time that i.m. injected T plus finasteride may be both the safest and most effective treatment for older hypogonadal men.”
U.S. Pharmacist Social Connect