Anti-Androgen Side Effects

Anti-androgen medications block the male hormone testosterone from binding to androgen receptors and are, therefore, useful in treating prostate cancer, because prostate cancer cells require testosterone to grow 2. Anti-androgen medications can be used alone, known as anti-androgen monotherapy (AAM) or in combination with LHRH (lutenizing hormone releasing hormone) antagonists, which actually reduce the amount of testosterone produced in the body—known as combined hormone blockade (CHB). Anti-androgen therapy is an effective treatment for prostate cancer but does have a number of side effects that are unpleasant and even possibly dangerous 2.

Mood/Cognitive Changes

Patients taking anti-androgen medications may experience changes in their mood or cognitive ability. Often the diagnosis of prostate cancer brings on feelings of depression and the medication can enhance this depression. Cognitive functions, according to a study published in the Deutsches Arzteblatt International, are impaired in approximately half of all patients taking anti-androgen medications 1. Although commonly overlooked, this side effect can be potentially serious.


Muscle mass and strength are affected by anti-androgen therapy 2. Patients taking anti-androgen medications alone are not as vulnerable to this side effect as those who are on the combined therapy. But according to Deutsches Arzteblatt International it is not uncommon for men to lose between 12 and 66 percent of their muscle strength due to the therapy 1.


Sexual side effects, more specifically loss of libido, are often the most disturbing side effects of anti-androgen therapy 2. Although there are medications to treat a loss of potency, or the inability to get an erection, there really is no treatment for a loss of libido (the general desire for sex).

The incidence of loss of libido is high, with up to 90 percent of patients on combined hormone blockage experiencing it, according to the Prostate Cancer Research Institute. Anti-androgen therapy alone has a lower incidence, with only about 50 percent of patients; however, this is still high enough to be a concern for most patients.


Gynecomastia, the condition where male breasts increase in size and become tender and or painful, is a common side effect of anti-androgen medications. About 50 to 60 percent of patients taking anti-androgen medications alone, according to the Prostate Cancer Research Institute, will experience this side effect 2. The incidence of gynecomastia is reduced to only 10 to 20 percent if the patient is treated with the combined therapy, adding in the LHRH.


Anti-androgen medications can cause:

  • a variety of common side effects including nausea
  • diarrhea
  • constipation
  • loss of appetite
  • dizziness
  • headache
  • trouble sleeping