Xtandi (Enzalutamide): What It Is and What to Expect

Xtandi is the brand name. Enzalutamide is the generic name. Prostate cancer feeds on androgens, chiefly testosterone. Older hormone treatments lower how much testosterone the body makes. Enzalutamide works one step further along: it blocks the receptor the hormone has to dock with, and it stops that receptor doing its job inside the cell.

The label's usual strength is 160 mg by mouth once a day, with or without food, though your urologist or oncologist may write something different for you — the bottle and the clinic instructions are what to follow. Swallow capsules or tablets whole with plenty of water. Do not chew, crush, split or open them.

• Castration-resistant prostate cancer, meaning cancer still growing despite testosterone already being low.
• Metastatic castration-sensitive prostate cancer, where the cancer has spread and still responds to hormone treatment.
• Non-metastatic castration-sensitive prostate cancer with biochemical recurrence at high risk of spreading. This means a rising PSA after surgery or radiation, with no cancer yet visible on scans.

That third group is the one people most often miss when they read about this drug.

For the first two groups, the label says enzalutamide is taken alongside a GnRH analogue injection, or after the testicles have been removed. Blocking the receptor is not enough on its own if testosterone is still being produced. Do not stop the injections because the tablets seem to be working.

The third group is different. Here enzalutamide can be given with or without a GnRH analogue. The label also allows a planned pause in this one group: after a sustained period with an undetectable PSA, treatment can be suspended and later restarted as PSA changes. The exact thresholds — and whether the pause applies to you at all — are your team's call from your own PSA history. Never pause or restart this drug on your own reading of a PSA result.

Seizures occurred in 0.6% of people across eight randomised trials, and they happened anywhere from 13 days to more than 6 years after starting. People at higher risk were generally left out of those trials, so tell your team about any history of seizure, head injury, stroke or brain metastases. A related condition called PRES, which brings headache, confusion, vision loss or seizures, is also listed.

Falls and fractures are a separate and more everyday problem. Bone protection, a look at your other medicines, and simple changes at home are all worth discussing early rather than after a fall.

Also on the label: allergic reactions, heart problems from reduced blood flow, and choking or difficulty swallowing the capsules.

Enzalutamide changes how the liver handles many other drugs, and some drugs change how it is handled in turn. Blood thinners such as warfarin, some heart and epilepsy medicines, and the herbal remedy St John's wort are common examples. It also interferes with certain digoxin blood tests, giving falsely high readings.

Give your pharmacist a full list, including anything bought without a prescription, and check before adding anything new.

Tiredness is the effect most men report, and it can be considerable. Hot flushes, high blood pressure, and aching joints and back are common too. Blood pressure is checked at visits. PSA and scans track whether it is working; a rising PSA is a reason for a conversation, not a reason to stop on your own.

• Call 911 or go to an emergency department if you have a seizure, you become suddenly confused or lose vision, your face or throat swells, you have crushing chest pain, or a fall leaves you unable to stand or bear weight.
• Call your care team the same day if a capsule sticks or you choke while swallowing it, you fall for no clear reason, or you have bone pain that starts after a knock and does not settle.
• Call your care team within a day or two if home blood pressure readings keep coming back high, or tiredness and unsteadiness are making you trip around the house.

Do not stop your GnRH injections on your own. Ask first.

https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b129fdc9-1d8e-425c-a5a9-8a2ed36dfbdf

https://www.cancer.gov/about-cancer/treatment/drugs/enzalutamide