Side effects of bicalutamide

The side effects of bicalutamide, a nonsteroidal antiandrogen (NSAA), including its frequent and rare side effects, have been well-studied and characterized. The most common side effects of bicalutamide monotherapy in men include breast tenderness, breast growth, feminization, demasculinization, and hot flashes. Less common side effects of bicalutamide monotherapy in men include sexual dysfunction, depression, fatigue, weakness, and anemia. Bicalutamide is well tolerated and has few side effects in women. General side effects of bicalutamide that may occur in either sex include diarrhea, constipation, abdominal pain, nausea, dry skin, itching, and rash. In men with prostate cancer, bicalutamide monotherapy has been found to increase the likelihood of death due to causes other than prostate cancer. Bicalutamide has been found to cause unfavorable liver changes in around 3 to 11% of people, with such changes necessitating discontinuation in approximately 1%. Rarely, bicalutamide has been associated with serious liver toxicity and lung disease, as well as sensitivity to light. It has also uncommonly been associated with hypersensitivity reactions. Bicalutamide has a theoretical risk of birth defects in male fetuses.

Central nervous system

Hot flashes In the Early Prostate Cancer (EPC) clinical trial programme, at 7.4 years follow-up, the rate of hot flashes was 9.2% for bicalutamide monotherapy relative to 5.4% for placebo, which was regarded as relatively low. In the LAPC subgroup of the EPC trial, the rate of hot flashes with bicalutamide monotherapy was 13.1% (relative to 50.0% for castration).

Sexual dysfunction Bicalutamide may cause sexual dysfunction, including decreased sex drive and erectile dysfunction. However, the rates of these side effects with bicalutamide monotherapy are very low. In the EPC trial, at 7.4 years follow-up, the rates of decreased libido and impotence were only 3.6% and 9.3% in the 150 mg/day bicalutamide monotherapy group relative to 1.2% and 6.5% for placebo, respectively. Similarly, in the trials of 150 mg/day bicalutamide monotherapy for advanced prostate cancer, fewer than 10% of men reported decreased sex drive or reduced erectile function as a side effect. About two-thirds of men in these trials, who had advanced prostate cancer and were of almost invariably advanced age, maintained sexual interest, while sexual function was slightly reduced by 18%. Most men experience sexual dysfunction only moderately or not at all with bicalutamide monotherapy, and the same is true during monotherapy with other NSAAs. Bicalutamide monotherapy at a dosage of 50 mg/day had no effect on nocturnal erections in men with prostate cancer. The preservation of sexual desire and function with NSAA monotherapy may be related to testosterone metabolites such as estradiol and the 3α-androstanediol maintaining these functions rather than the androgen receptor or to bicalutamide and other NSAAs possibly incompletely blocking the androgen receptor in the brain. Similarly to in men, bicalutamide has been associated with minimal or no sexual dysfunction in women. A phase III clinical study of 50 mg/day bicalutamide in conjunction with a combined oral contraceptive in women with severe hirsutism due to polycystic ovary syndrome (PCOS) carefully assessed the side effect of decreased libido and found that the incidence with bicalutamide did not differ from the control group. Minimal rates of reduced sex drive have also been associated with the related NSAA flutamide. These findings are in accordance with the fact that women with complete androgen insensitivity syndrome (CAIS) show normal sexual function in spite of complete loss of androgen receptor (AR) signaling. They are also in accordance with a variety of findings concerning testosterone levels and sexual function in premenopausal women, in which no change in parameters of sexual function, including libido, have been observed in association with increases or decreases in testosterone levels. It appears that testosterone levels within the normal physiological range are not importantly involved in sexual desire or function in women.

Psychiatric conditions At 5.3 years follow-up, the incidence of depression was 5.5% for bicalutamide monotherapy relative to 3.0% for placebo in the EPC trial, and the incidence of asthenia (weakness or fatigue) was 10.2% for bicalutamide monotherapy relative to 5.1% for placebo. Rarely, bicalutamide has been associated with hallucinations. This is thought to be secondary to AR antagonism.

Breasts and reproductive system

Breast changes

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