Approved indications: In the United States, Xtandi (enzalutamide) is FDA‑approved for adults with castration‑resistant prostate cancer (both non‑metastatic and metastatic), metastatic castration‑sensitive prostate cancer (mCSPC), and non‑metastatic castration‑sensitive prostate cancer with biochemical recurrence at high risk for metastasis (high‑risk nmCSPC with BCR).

Off‑label uses: Outside these prostate cancer settings, Xtandi is mainly used in clinical trials (for example, in certain androgen‑receptor–positive solid tumors), and routine off‑label use in other cancers is uncommon and generally reserved for specialist centers when standard options are exhausted, reflecting limited evidence.

Efficacy expectations:

• In advanced castration‑resistant and metastatic castration‑sensitive prostate cancer, Xtandi plus standard hormone‑lowering therapy significantly delays radiographic progression and improves overall survival compared with placebo or older hormone therapies.
• In high‑risk nmCSPC with biochemical recurrence, Xtandi (with or without a GnRH analog) markedly prolongs metastasis‑free survival versus placebo plus GnRH therapy.
• PSA levels commonly begin to fall within weeks to a few months; imaging is usually checked every several months to confirm disease control, and many patients can remain on therapy for years if it is effective and tolerated.
• Compared with other modern androgen‑receptor–pathway inhibitors (such as abiraterone, apalutamide, and darolutamide), overall efficacy is broadly similar, and drug choice is often based on side‑effect profile, need for steroids (with abiraterone), comorbidities, and patient preference rather than large differences in effectiveness.

Typical adult dosing: The standard dose for all approved prostate cancer indications is 160 mg of Xtandi taken by mouth once daily, with or without food, continued until disease progression or unacceptable toxicity.

How to take it:

• Take Xtandi at the same time each day.
• Swallow capsules or tablets whole with a sufficient amount of water; do not chew, cut, crush, dissolve, or open them.
• It can be taken with or without food.

Use with hormone‑lowering therapy:

• For castration‑resistant prostate cancer (CRPC) and metastatic castration‑sensitive prostate cancer (mCSPC), continue a GnRH analog (such as leuprolide) or ensure you have had surgical castration while on Xtandi.
• For high‑risk nmCSPC with biochemical recurrence, Xtandi may be used with or without a GnRH analog; in eligible patients, treatment can sometimes be paused when PSA becomes undetectable after about 36 weeks and restarted if PSA rises again to specified thresholds.

Dose adjustments:

• If you develop a severe (Grade 3 or higher) or intolerable side effect, your clinician may stop Xtandi for about a week or until symptoms improve, then restart it at the same dose or a reduced dose (for example, 120 mg or 80 mg daily).
• If you must take a strong CYP2C8 inhibitor (such as gemfibrozil), the Xtandi dose is typically reduced to 80 mg daily; if you must take a strong CYP3A4 inducer (such as rifampin), the dose may be increased up to 240 mg daily, with careful supervision.

Missed dose:

• If you remember later the same day, take your usual dose as soon as you remember.
• If you miss it for the entire day, skip that day and take your normal dose at the regular time the next day; do not take extra tablets to make up for a missed dose.

Overdose:

• If you take more than your prescribed dose, call your doctor or go to the nearest emergency room right away, as overdose may increase the risk of seizures and other serious side effects.

Common side effects: The most frequent side effects include fatigue or weakness, muscle and joint pain, hot flashes, constipation or diarrhea, decreased appetite, headache, swelling, high blood pressure, bleeding or bruising, falls, and bone fractures; these usually start in the first weeks to months of treatment and are often mild to moderate but can occasionally be more severe.

• Blood tests may show changes such as lower hemoglobin or white blood cell counts and changes in blood sugar or electrolytes, so your clinician may check labs periodically.

Serious or rare adverse effects (seek urgent medical care):

• Seizures (reported in about 0.6% of patients overall; risk is higher if you have conditions or medicines that lower the seizure threshold).
• Posterior reversible encephalopathy syndrome (PRES), a rare brain condition causing sudden severe headache, confusion, vision changes, or seizures.
• Serious allergic reactions with swelling of the face, lips, tongue, or throat.
• Heart problems, including ischemic heart disease or heart attack, with chest pain, shortness of breath, or sudden worsening fatigue.
• Severe swallowing difficulty or choking related to capsule or tablet size.

Warnings and precautions:

• Seizure risk: Use caution if you have a history of seizures, stroke, brain injury, brain tumors, or take medicines that lower the seizure threshold; avoid activities where sudden loss of consciousness could cause serious harm.
• Cardiovascular disease and hypertension: Xtandi can raise blood pressure and may worsen heart disease; blood pressure and cardiovascular symptoms should be monitored and risk factors optimized.
• Bones and falls: Xtandi increases the risk of falls and fractures; clinicians often assess fall risk and may suggest bone‑strengthening measures, calcium/vitamin D, or bone‑targeted drugs when appropriate.
• Pregnancy and breastfeeding: Xtandi is not indicated for women and can cause fetal harm; men with partners who can become pregnant should use effective contraception during treatment and for a period after the last dose, and women should not handle damaged capsules or tablets if pregnant.
• Age limits: Safety and effectiveness have not been established in children; Xtandi is used in adults with prostate cancer.
• Kidney and liver disease: No routine dose adjustment is required for mild to moderate kidney impairment; significant liver disease or very poor kidney function may warrant closer monitoring and individualized dosing.
• Fertility: Xtandi may impair male fertility and the ability to father children.

Relative safety compared with similar drugs: Xtandi shares many side effects with other androgen‑receptor–pathway inhibitors; compared with abiraterone, it generally has less liver and mineralocorticoid‑related toxicity but more concern for seizures and falls, while darolutamide tends to have fewer central‑nervous‑system effects, so the safest choice varies by a person’s other medical problems.

Reporting and staying informed: Side effects should be reported promptly to your healthcare provider; you can also report serious adverse effects directly to the FDA MedWatch program by phone (1‑800‑FDA‑1088) or online, and updated safety information is available through the FDA website and the manufacturer’s prescribing information.

Major drug and supplement interactions:

• CYP2C8 inhibitors: Strong inhibitors such as gemfibrozil can greatly increase Xtandi levels and side effects; they should generally be avoided or require a lower Xtandi dose.
• CYP3A4 inducers: Strong inducers such as rifampin, carbamazepine, phenytoin, and St. John’s wort can lower Xtandi levels and reduce its effectiveness; they should be avoided or require a higher Xtandi dose under specialist guidance.
• Effect of Xtandi on other drugs: Xtandi is a strong inducer of CYP3A4 and a moderate inducer of CYP2C9 and CYP2C19, so it can lower blood levels and effectiveness of many medicines, including some anticoagulants (such as warfarin), anti‑seizure medicines, blood pressure drugs, statins, some antidepressants, benzodiazepines, and proton‑pump inhibitors; additional INR monitoring is advised if used with warfarin.
• Medicines that lower seizure threshold (for example, certain antidepressants, antipsychotics, tramadol, other CNS stimulants) may further increase seizure risk when combined with Xtandi and should be reviewed carefully.
• OTC drugs and herbals: Always review non‑prescription medicines (such as NSAIDs, cold remedies) and herbal products, especially enzyme‑inducing agents like St. John’s wort.
• Food and alcohol: Xtandi may be taken with or without food; alcohol has no specific known pharmacokinetic interaction but can worsen dizziness, fatigue, or seizure risk and should be used cautiously.
• Diagnostic tests: Xtandi can interfere with certain digoxin immunoassays, causing falsely elevated digoxin levels on some lab tests.

Conditions requiring extra caution:

• History of seizures, stroke, significant head injury, brain tumors, or brain metastases.
• Uncontrolled high blood pressure, prior heart attack, heart failure, or significant coronary artery disease.
• Osteoporosis, prior fragility fractures, or high fall risk.
• Moderate to severe liver impairment or very poor kidney function (dosing and monitoring may need adjustment).
• Need for medicines that strongly interact through CYP2C8, CYP3A4, CYP2C9, or CYP2C19, where alternatives may be preferable.

Monitoring needs:

• Regular blood pressure checks and cardiovascular symptom review.
• Periodic blood tests, such as complete blood counts and chemistry panels, especially if you have other illnesses or take interacting medicines.
• PSA measurements and imaging (such as bone scans or CT/MRI) to track how well the cancer is responding.
• Assessment of falls and bone health, with bone‑protective strategies when appropriate.

Q: What is Xtandi used for?
A: Xtandi (enzalutamide) is an oral androgen‑receptor blocker used in adults to treat advanced forms of prostate cancer, including castration‑resistant disease, metastatic castration‑sensitive disease, and certain high‑risk non‑metastatic cases with biochemical recurrence.

Q: How long does it take for Xtandi to start working?
A: Many men see their PSA level begin to fall within a few weeks to a few months after starting Xtandi, but improvements on imaging or in symptoms may take longer and are usually checked every several months.

Q: Do I still need hormone shots (GnRH therapy) while on Xtandi?
A: For castration‑resistant and metastatic castration‑sensitive prostate cancer, you usually must continue your GnRH injections or have had surgical castration; in high‑risk non‑metastatic castration‑sensitive disease with biochemical recurrence, Xtandi may be used with or without GnRH shots depending on your treatment plan.

Q: Can I take Xtandi with food and my other daily medicines?
A: Xtandi can be taken with or without food, but many medicines interact with it, so your healthcare team should review all prescription drugs, over‑the‑counter products, and supplements you use to adjust doses or avoid unsafe combinations.

Q: What should I do if I miss a dose of Xtandi?
A: If you remember later the same day, take your usual dose as soon as you remember; if you miss it for the entire day, skip that day and take your regular dose the next day without doubling up.

Q: Will Xtandi affect my ability to have children or my sexual function?
A: Xtandi can reduce male fertility and, together with ongoing hormone‑lowering therapy, often lowers sex drive and can cause erectile difficulties, so men who may want children in the future should discuss sperm banking and options for managing sexual side effects before or during treatment.

Storage: Store Xtandi capsules or tablets at room temperature 68°F to 77°F (20°C to 25°C), in a dry place, in the tightly closed original bottle, and keep it out of the reach of children and pets.

Handling: Keep the bottle tightly capped between doses, avoid storing it in places with high humidity such as bathrooms, and do not use the medicine after the expiration date on the package.

Disposal: If you have unused or expired Xtandi, use a community drug take‑back program if available, or ask your pharmacist how to dispose of it; if no program is available, mix the tablets or capsules (do not crush or open them) with an unwanted substance like coffee grounds or cat litter in a sealed bag or container before placing it in household trash, and do not flush it down the toilet unless specifically instructed.