Bicalutamide Side Effects: What to Expect and When to Call Your Doctor

If your doctor has prescribed bicalutamide (brand name Casodex) as part of your prostate cancer treatment, you’ve probably already been told it’s usually combined with another medication called an LHRH analog. That combination is effective, but it also means understanding bicalutamide side effects on their own can be confusing — some symptoms come from the bicalutamide, some from the LHRH analog, and some from the two working together. Here’s what the evidence actually shows about what to expect, from the most common effects to the rarer ones worth watching for.

What Is Bicalutamide Used For?

Bicalutamide belongs to a class of medications called anti-androgens, and according to Drugs.com, it’s used in patients with advanced prostate cancer in combination with an LHRH analog — a type of hormone therapy that lowers testosterone production. Because prostate cancer cells typically rely on testosterone to grow, combining an LHRH analog with an anti-androgen like bicalutamide is a strategy to block that growth signal more completely than either medication would on its own. This combined approach is effective, but it also means many of the side effects below are closely tied to how both medications work together to lower androgen activity in the body.

Dosing matters here too. Drugs.com notes that the risk of interstitial lung disease rises most often at doses greater than 50 mg — a detail worth being aware of if your prescribed dose changes over the course of treatment, or if you’re being treated with a higher-dose regimen for a different reason. If you’re ever unsure why your dose is what it is, or whether a dose change might affect your side-effect risk, that’s a reasonable question to bring to your prescribing doctor rather than guess at.

The Most Common Side Effect: Hot Flashes

Hot flashes stand out clearly as the single most frequent reaction. Drugs.com lists hot flashes at 53% in the “very common” category (10% or more) for patients taking bicalutamide combined with an LHRH analog — meaning more than half of patients in the data behind this labeling experienced them. This isn’t unique to bicalutamide; it reflects the broader effect of lowering androgen levels, which is also why hot flashes are a well-known side effect across other prostate cancer hormone therapies. If hot flashes become disruptive to sleep or daily life, it’s worth raising with your doctor, since there are strategies — from simple lifestyle adjustments to, in some cases, medication — that can help manage them.

Other Very Common Side Effects (10% or More)

Beyond hot flashes, Drugs.com’s prescribing data lists several other effects in the “very common” category for patients on the bicalutamide-plus-LHRH-analog combination:

• Pain (35%) and back pain (25%)
• Asthenia, or general weakness (22%)
• Constipation (22%)
• Pelvic pain (21%)
• Infection (18%)
• Nausea (15%)
• Peripheral edema, or swelling in the limbs (13%)
• Dyspnea, or shortness of breath (13%)
• Diarrhea (12%)
• Nocturia, or needing to urinate during the night (12%)
• Hematuria, or blood in the urine (12%)
• Abdominal pain (11%)
• Anemia (11%)

It’s worth keeping in mind that some of these — particularly pain, back pain, and pelvic pain — can also reflect the underlying prostate cancer itself rather than the medication alone, which is part of why your care team tracks these symptoms over time rather than assuming every change is drug-related.

Common Side Effects (1% to 10%)

Drugs.com categorizes a longer list of effects as “common,” occurring in roughly 1% to 10% of patients, without more specific percentages attached. These include:

• Breast changes. Gynecomastia (breast swelling) and breast pain or tenderness — the patient-facing information notes this can affect men taking the medication.
• Sexual and urinary changes. Impotence, decreased libido, urinary frequency, and urinary retention.
• Cardiovascular effects. Hypertension, angina pectoris, congestive heart failure, myocardial infarction, and syncope (fainting).
• Weight changes. Both weight loss and weight gain are listed.
• Neurological and mood effects. Headache, neuropathy, insomnia, anxiety, depression, confusion, and somnolence (drowsiness).
• Skin changes. Rash, sweating, dry skin, alopecia (hair thinning or loss), and pruritus (itching).
• Respiratory symptoms. Cough and pneumonia.
• Blood test changes. Decreased hemoglobin, decreased white blood cell count, and elevated creatinine.
• Eye changes. A specified type of cataract.

Less common still — in the 0.1% to 1% range — Drugs.com lists lung disorder, asthma, nosebleeds (epistaxis), and sinusitis.

Liver Effects to Watch For

Liver changes are specifically flagged as a precaution. Drugs.com’s patient guidance states plainly: check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin, since these could be symptoms of a serious liver problem. On the clinical data side, increased liver enzyme tests, elevated alkaline phosphatase, elevated AST, elevated ALT, and elevated bilirubin are all listed in the “common” category. Because of this, your doctor will likely want to check your progress at regular visits, which may include blood tests to monitor for liver-related changes or other effects that wouldn’t necessarily cause noticeable symptoms on their own.

Serious but Less Common Risks

A few effects are rarer but more serious, and worth knowing about even if they’re unlikely to affect you directly:

• Interstitial lung disease. Drugs.com describes this as “sometimes fatal,” including interstitial pneumonitis and pulmonary fibrosis, occurring most often at doses greater than 50 mg. Persistent new or worsening shortness of breath or cough should be reported to your doctor promptly.
• Increased bleeding risk with blood thinners. Bicalutamide can interact with coumarin-type anticoagulants such as warfarin, increasing PT/INR measurements, and serious bleeding has been reported with this combination. If you take a blood thinner, make sure your prescribing doctors know about both medications.
• Photosensitivity. Reported after the drug reached the market, meaning increased sensitivity to sunlight is possible, even though it isn’t common.

Fertility and Pregnancy Considerations

Bicalutamide carries specific precautions related to reproduction. Drugs.com notes it may cause some men to become infertile, at least temporarily, while on treatment. Because the medication isn’t intended for use by women, women who are or may become pregnant should not use it, and male patients with female partners are advised to use effective birth control during treatment and for 130 days after the last dose. The medication can also affect the results of a prostate specific antigen (PSA) test, which is worth keeping in mind since PSA is often used to monitor how prostate cancer treatment is working — your doctor will interpret PSA results with your bicalutamide treatment in mind.

Managing the More Common Side Effects

Most people on bicalutamide don’t experience the rarer, more serious reactions described above — but the more common effects, like hot flashes, fatigue, and digestive changes, are common enough that it’s worth knowing there are usually ways to make them more manageable rather than simply enduring them. Hot flashes often respond, at least partially, to simple measures like dressing in layers, keeping your bedroom cooler at night, and avoiding common triggers like caffeine, alcohol, and spicy food; for hot flashes that are significantly disrupting sleep or daily functioning, some doctors will discuss additional medication options. Constipation, listed among the very common effects, usually responds to the same basic steps used for constipation generally — adequate fluid intake, dietary fiber, and staying as physically active as your situation allows, though it’s worth asking your doctor before starting any new over-the-counter remedy to make sure it won’t interact with your other medications. Fatigue and general weakness (asthenia) are also common enough that pacing activity throughout the day, rather than pushing through long stretches at once, tends to help more than trying to power through it. None of these strategies replace medical guidance, but raising them proactively at your appointments — rather than waiting to be asked — tends to get better results than mentioning them only in passing.

When to Call Your Doctor

Call your doctor promptly if you notice any signs of a liver problem — upper stomach pain or tenderness, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellowing of the skin or eyes. The same goes for new or worsening shortness of breath or persistent cough, given the rare but serious risk of interstitial lung disease, and for any unusual bleeding or bruising, especially if you’re also taking a blood thinner. More routine side effects — hot flashes, fatigue, mild digestive changes — are still worth mentioning at your regular visits, since your care team may have ways to help you manage them even if they aren’t dangerous on their own. And because bicalutamide is typically used alongside an LHRH analog for advanced prostate cancer, regular follow-up with your care team matters not just for side effects, but for monitoring how the overall treatment is working.

Frequently Asked Questions

What is the most common side effect of bicalutamide?

Hot flashes are by far the most common, affecting 53% of patients taking bicalutamide in combination with an LHRH analog, according to Drugs.com’s prescribing data. This reflects the broader effect of lowering androgen levels as part of prostate cancer hormone therapy.

Does bicalutamide cause breast growth in men?

It can. Gynecomastia (breast swelling) and breast pain or tenderness are both listed as common side effects, occurring in roughly 1% to 10% of patients according to Drugs.com. If breast changes are bothersome, it’s worth discussing with your doctor, since there may be ways to manage or monitor this effect.

Is bicalutamide hard on the liver?

Liver-related changes are a known precaution rather than a rare oddity. Increased liver enzyme levels, elevated ALT and AST, and elevated bilirubin are all listed as common, and your doctor will likely monitor liver function with periodic blood tests. Seek prompt medical attention for symptoms like yellowing skin or eyes, dark urine, or pain in the upper stomach.

Can bicalutamide affect my PSA test results?

Yes. Drugs.com notes that bicalutamide may affect the results of a prostate specific antigen (PSA) test. Since PSA is commonly used to track how prostate cancer treatment is working, your doctor will take your bicalutamide use into account when interpreting your results.

Does bicalutamide cause permanent infertility?

Drugs.com describes the infertility risk as affecting some men, “at least temporarily,” rather than stating it’s always permanent. If fertility is a concern for you, it’s worth discussing options and expectations with your doctor before or early in treatment.

This article is for general educational purposes and isn’t a substitute for personalized medical advice. Always follow the guidance of your prescribing doctor, and report any new or concerning symptoms promptly rather than waiting for your next scheduled visit.

Bicalutamide is generally well tolerated when used as directed, but like any hormone therapy for prostate cancer, it comes with a predictable set of effects — hot flashes chief among them — along with a smaller number of more serious risks worth knowing the warning signs for. Staying in regular contact with your care team, reporting new symptoms as they come up, and keeping up with recommended blood work are the best ways to catch anything that needs attention early, while still getting the full benefit of your treatment plan.