What is Androcur (Cyproterone acetate)?

What is Androcur (Cyproterone Acetate)?

Androcur (cyproterone acetate) is a steroidal antiandrogen medication that blocks androgen receptors and suppresses testosterone production through antigonadotropic effects, primarily used for treating androgen-sensitive metastatic prostate cancer and as part of gender-affirming hormone therapy for transgender women. 1, 2

Mechanism of Action

Cyproterone acetate works through two distinct pathways 2:

• Direct competitive inhibition of androgen receptor binding at target tissues, blocking the effects of testosterone and dihydrotestosterone 3, 4
• Negative feedback suppression of the hypothalamic-pituitary axis, reducing LHRH release and thereby decreasing testicular testosterone production 2, 5

This dual mechanism makes it unique as the only antiandrogen capable of achieving complete androgen blockade as monotherapy 6.

Primary Clinical Indications

Prostate Cancer

• Second-line hormonal therapy for androgen-sensitive metastatic prostate cancer in Europe and Canada 1, 7
• Prevention of tumor flare when initiating LHRH agonist therapy, typically given for 2-4 weeks before and during early LHRH agonist treatment 1, 5
• Suppression of hot flashes associated with orchiectomy or LHRH agonist therapy 5, 6
• Typical dosing: 200-300 mg daily orally or 300 mg weekly intramuscularly 3, 7

Important caveat: When used alone for metastatic prostate cancer, cyproterone acetate is less effective than goserelin in delaying disease progression 1, 2. It shows no survival advantage over diethylstilbestrol but has fewer cardiovascular side effects 2, 5.

Gender-Affirming Hormone Therapy

• Antiandrogen component in hormone therapy for transgender women/transfeminine individuals 1, 2
• Recommended by the World Professional Association for Transgender Health 1

Other Androgen-Dependent Conditions

• Treatment of severe acne, seborrhea, hirsutism, and androgenic alopecia 3
• Management of precocious puberty 3
• Treatment of sexual disorders and paraphilias in men, where it reduces libido and erectile function within approximately 14 days at doses of 100-200 mg daily 3, 4

Critical Safety Monitoring Requirements

Mandatory Baseline and Ongoing Tests

Hepatic monitoring is essential due to risk of severe hepatotoxicity 1:

• Liver function tests at baseline and every 3-6 months 1
• Immediate discontinuation required if fulminant hepatic failure or severe hepatotoxicity develops 1

Hematologic monitoring 1:

• Complete blood count at baseline to establish hemoglobin and hematocrit
• Ongoing monitoring every 3-6 months for anemia
• Discontinue if severe anemia develops 1

Adrenal function assessment 1:

• Baseline and periodic monitoring throughout treatment
• Discontinue if significant adrenal suppression occurs 1

Absolute Contraindications

Cyproterone acetate is contraindicated in patients with hereditary angioedema 8, 1, 2:

• It has been specifically reported to worsen HAE-C1-INH (hereditary angioedema caused by C1 inhibitor deficiency) 8
• This is due to its potent antiandrogenic properties combined with strong antigonadotropic effects 8

Use with extreme caution in patients with pre-existing liver disease due to hepatotoxicity risk 1, 2.

Common Side Effects

Hormonal Effects

• Loss of libido and erectile dysfunction (onset within 14 days, reversible upon discontinuation) 3
• Gynecomastia and breast tenderness in approximately 18-20% of patients 3, 5
• Hot flushes (though less common than with other androgen deprivation therapies) 5

Non-Specific Effects

• Tiredness, lack of drive, listlessness, and depressive moods 3
• Infertility (reversible) 5
• Cardiovascular complications in approximately 10% of treated men 5

Discontinuation Considerations

Gradual tapering is strongly preferred over abrupt discontinuation 9:

• For high doses: reduce by 50 mg every 2-4 weeks 9
• For moderate doses: reduce by 25 mg every 2-4 weeks 9
• For low doses: reduce by 12.5 mg every 2-4 weeks 9

Special consideration for transgender patients: Discontinuation may result in significant exacerbation of gender dysphoria, depression, and/or anxiety 1, 9. This requires careful clinical judgment and patient counseling.

Clinical Effectiveness

Approximately 75-80% of patients respond to cyproterone acetate therapy for its indicated uses 3. The drug is generally well tolerated when appropriate monitoring is maintained 2, 3.