Usage
Bicalutamide is prescribed for the treatment of advanced prostate cancer. It’s used in combination with a luteinizing hormone-releasing hormone (LHRH) analog or surgical castration. Its pharmacological classification is antiandrogen, specifically a non-steroidal antiandrogen. Bicalutamide works by blocking the effects of testosterone, thereby inhibiting the growth and spread of prostate cancer cells.
Alternate Names
Bicalutamide is also known by its brand name Casodex. Other brand names might exist internationally.
How It Works
Pharmacodynamics: Bicalutamide competitively binds to androgen receptors, preventing testosterone from binding and stimulating the growth of prostate cancer cells. This leads to tumor regression. Discontinuation of bicalutamide may cause an antiandrogen withdrawal syndrome in some patients.
Pharmacokinetics:
- Absorption: Bicalutamide is well-absorbed orally, and food doesn’t significantly affect its bioavailability.
- Metabolism: It is extensively metabolized in the liver, primarily by CYP3A4.
- Elimination: Bicalutamide is eliminated through both hepatic and renal routes, with a half-life of approximately one week. The (R)-enantiomer is the primary active form.
Mode of Action: Bicalutamide is a racemic mixture, with the (R)-enantiomer primarily responsible for its antiandrogenic activity. It acts as a competitive inhibitor of androgen receptors, preventing androgens from binding and activating gene expression. This inhibition leads to reduced growth and proliferation of prostate cancer cells.
Dosage
Standard Dosage
Adults: 50 mg orally once daily, with or without food. Treatment should be started concurrently with LHRH analog therapy or surgical castration. Ideally, bicalutamide should be taken at the same time each day.
Children: Bicalutamide is contraindicated in children.
Special Cases:
- Elderly Patients: No dose adjustment is generally required.
- Patients with Renal Impairment: No dose adjustment is necessary.
- Patients with Hepatic Dysfunction: No dose adjustment is necessary for mild hepatic impairment. Caution is advised in patients with moderate to severe hepatic impairment, as bicalutamide accumulation may occur. Close monitoring of liver function is recommended.
- Patients with Comorbid Conditions: Close monitoring of blood glucose is recommended in patients with diabetes receiving bicalutamide in combination with LHRH agonists. Caution is warranted in patients with cardiovascular disease due to potential fluid retention.
Clinical Use Cases
Bicalutamide is not indicated for use in clinical scenarios like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. Its sole clinical use is in the management of advanced prostate cancer.
Dosage Adjustments
Dose adjustments may be necessary for patients with moderate to severe hepatic impairment. Close monitoring of liver function tests and clinical response is necessary.
Side Effects
Common Side Effects:
Hot flashes, pain (back, pelvic, general), weakness, nausea, diarrhea, constipation, infections, peripheral edema, dyspnea, dizziness, hematuria, nocturia, anemia, gynecomastia (breast enlargement), breast pain.
Rare but Serious Side Effects:
Severe allergic reactions (angioedema, urticaria), hepatotoxicity (jaundice, elevated liver enzymes), interstitial lung disease, bleeding (especially with concomitant anticoagulant use), QT prolongation.
Long-Term Effects:
Potential long-term effects include gynecomastia, liver dysfunction, cardiovascular complications (fluid retention), and metabolic changes (glucose intolerance).
Adverse Drug Reactions (ADR):
Severe allergic reactions, hepatotoxicity, interstitial lung disease, and significant bleeding events require immediate medical attention.
Contraindications
Absolute contraindications include hypersensitivity to bicalutamide, use in females (including during pregnancy and breastfeeding), and pediatric use. Co-administration with terfenadine, astemizole, or cisapride is contraindicated.
Drug Interactions
Bicalutamide interacts with several medications, including:
- CYP3A4 Inhibitors: These can increase bicalutamide levels.
- Coumarin Anticoagulants (e.g., warfarin): Bicalutamide can increase the effects of these drugs, leading to an increased bleeding risk.
- Drugs that Prolong the QT Interval: Concomitant use should be carefully evaluated.
- LHRH Agonists: May affect glucose tolerance.
Interactions with other commonly prescribed medications, OTC drugs, supplements, and lifestyle factors (alcohol, smoking, grapefruit juice) should be considered.
Pregnancy and Breastfeeding
Bicalutamide is contraindicated in females and must not be used during pregnancy or breastfeeding. It can cause fetal harm and may be excreted in breast milk.
Drug Profile Summary
- Mechanism of Action: Non-steroidal antiandrogen; competitively inhibits androgen receptors.
- Side Effects: Hot flashes, pain, weakness, gastrointestinal issues, gynecomastia, breast pain, hepatotoxicity, allergic reactions, interstitial lung disease, bleeding.
- Contraindications: Hypersensitivity, female patients, pregnancy, breastfeeding, pediatric use, concomitant use with terfenadine, astemizole, or cisapride.
- Drug Interactions: CYP3A4 inhibitors, coumarin anticoagulants, QT-prolonging drugs, LHRH agonists.
- Pregnancy & Breastfeeding: Contraindicated.
- Dosage: 50 mg orally once daily with or without food.
- Monitoring Parameters: Liver function tests, PSA levels, blood glucose, PT/INR (if on anticoagulants), signs and symptoms of adverse effects.
Popular Combinations
Bicalutamide is commonly used in combination with LHRH analogs (e.g., goserelin, leuprolide) for advanced prostate cancer. This combination, known as combined androgen blockade (CAB), provides more complete androgen suppression than either drug alone.
Precautions
- Baseline and regular monitoring of liver function tests are recommended.
- Caution is advised in patients with hepatic impairment.
- Monitor blood glucose in diabetic patients receiving concomitant LHRH agonists.
- Monitor for signs and symptoms of gynecomastia, breast pain, bleeding, and allergic reactions.
- Patients should avoid excessive sun exposure.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Bicalutamide?
A: The standard dose for adult males is 50 mg orally once daily, taken with or without food. It is contraindicated in children and females.
Q2: How does Bicalutamide work?
A: Bicalutamide is an antiandrogen that competitively binds to androgen receptors, preventing testosterone from stimulating prostate cancer cell growth.
Q3: What are the most common side effects of Bicalutamide?
A: Common side effects include hot flashes, pain, weakness, gastrointestinal disturbances, gynecomastia, and breast pain.
Q4: What are the serious side effects of Bicalutamide?
A: Rare but serious side effects include hepatotoxicity, interstitial lung disease, severe allergic reactions, and bleeding (especially with concomitant warfarin use).
Q5: Can Bicalutamide be used in patients with liver disease?
A: It should be used with caution in patients with moderate to severe hepatic impairment, as drug accumulation may occur. Close monitoring of liver function is recommended. No dose adjustment is needed in mild hepatic impairment.
Q6: Are there any drug interactions I should be aware of with Bicalutamide?
A: Yes, Bicalutamide interacts with several medications, including CYP3A4 inhibitors, coumarin anticoagulants, and drugs that prolong the QT interval.
Q7: Can Bicalutamide be used during pregnancy or breastfeeding?
A: No, Bicalutamide is contraindicated in females and must not be used during pregnancy or breastfeeding.
Q8: What should I monitor in a patient taking Bicalutamide?
A: Monitor liver function tests, PSA levels, blood glucose (if also receiving LHRH agonists), PT/INR (if on anticoagulants), and signs and symptoms of adverse effects.
Q9: Why is Bicalutamide often prescribed with an LHRH agonist?
A: Combining bicalutamide with an LHRH agonist (combined androgen blockade) provides more complete suppression of androgens and is more effective in treating advanced prostate cancer than either drug alone.
Q10: What should I tell my patient about taking Bicalutamide?
A: Inform patients about potential side effects, drug interactions, the importance of adherence to the prescribed regimen, and the need for regular monitoring and follow-up appointments. Emphasize that the medication should not be shared with others and that any unusual symptoms should be reported immediately.
