What are the side effects of Enzalutamide?

Enzalutamide is a type of hormone therapy for men with prostate cancer that has spread to other parts of the body (advanced prostate cancer) and has stopped responding to other types of hormone therapy.

It works by blocking the effect of the hormone testosterone on prostate cancer cells. Without testosterone, the prostate cancer cells can’t grow, even if they have spread to other parts of the body.Enzalutamide has been shown to help some men live longer. It can also help to treat or delay symptoms, such as pain and bone problems.

What are the side effects?

Notable side effects of enzalutamide seen in clinical trials have included gynecomastia, breast pain/tenderness, fatigue, diarrhea, hot flashes, headache, sexual dysfunction, and, less commonly, seizures.  Other "common" side effects reported in clinical trials have included neutropenia, visual hallucinations, anxiety, cognitive disorder, memory impairment, hypertension, dry skin, and pruritus (itching). Enzalutamide monotherapy is regarded as having a moderate negative effect on sexual function and activity, significantly less than that of GnRH analogues but similar to that of other NSAAs such as bicalutamide.

Central adverse effects

Seizures have occurred in approximately 1% of patients treated with enzalutamide in clinical trials. This is thought to be due to enzalutamide crossing the blood–brain barrier and exerting off-target binding to and inhibition of the GABAA receptor in the central nervous system (it has been found to inhibit the GABAA receptor in vitro (IC50 = 3.6 μM) and induces convulsions in animals at high doses).

In addition to seizures, other potentially GABAA receptor-related side effects observed with enzalutamide treatment in clinical trials have included anxiety, insomnia, vertigo, paresthesia, and headache. Due to its ability to lower the seizure threshold, patients with known seizure disorders or brain injury should be closely monitored during enzalutamide treatment. NSAA-induced seizures are responsive to benzodiazepine treatment, and it has been suggested that GABAA receptor inhibition by enzalutamide could be treated with these drugs.

Speak to your doctor or specialist nurse if you have any side effects from taking enzalutamide, even if they’re not listed here. They may offer you other treatments to help manage any side effects.