What is the recommended dose of Arimidex (anastrozole) for a male patient?

Anastrozole Dosing for Men

For men on testosterone replacement therapy with elevated estrogen, anastrozole 0.5 mg three times weekly (not daily) is the recommended regimen, as this effectively reduces estradiol while minimizing the risk of excessive suppression and bone loss. 1

Critical Pre-Treatment Requirements

Before prescribing anastrozole to any male patient, you must:

• Measure baseline bone mineral density (BMD) and assess fracture risk—this is mandatory, not optional 2, 1
• Do not prescribe if severe osteoporosis is present (T-score < -4 or >2 vertebral fractures), as this is an absolute contraindication 2, 1, 3
• Use extreme caution with moderate bone density loss; consider concurrent bisphosphonates or RANKL inhibitors 2, 1, 3

Dosing Regimen for Men

The evidence-based dose for men on testosterone therapy is 0.5 mg three times weekly (Monday/Wednesday/Friday schedule), NOT the 1 mg daily dose used in women. 1 This intermittent dosing:

• Reduces median estradiol from 65 pg/mL to 22 pg/mL (P < 0.001) 1
• Maintains stable testosterone levels (616 ng/dL pre-treatment vs 596 ng/dL post-treatment) 1
• Limits excessive estradiol suppression compared to daily dosing 1

Alternative Strategy: Optimize Testosterone First

Before adding anastrozole, consider reducing testosterone dosing to achieve mid-normal range levels (400-600 ng/dL) to minimize aromatization. 1, 3 This avoids polypharmacy and additional risks.

Mandatory Bone Protection Protocol

All men receiving anastrozole must:

• Take calcium and vitamin D supplementation 2, 1, 3
• Engage in regular weight-bearing exercise 2, 1, 3
• Repeat BMD measurement annually if continuing long-term therapy 1

Expected Adverse Effects to Counsel About

• Joint stiffness and arthralgias are very common 1, 4, 3
• Vasomotor symptoms (hot flashes) 1, 4
• Hypertension and potential cardiovascular effects 1, 4

Monitoring Protocol

• Check testosterone and estradiol levels at 2-3 months after initiation 3
• Then monitor every 6-12 months once stable 1, 3
• Target mid-normal testosterone range (500-600 ng/dL) 3
• Monitor for musculoskeletal symptoms 1

Fertility Consideration

If fertility preservation is a concern, anastrozole may be preferable to testosterone alone, as it can improve spermatogenesis by increasing endogenous testosterone while reducing estradiol (sperm concentration increased from 5.5 to 15.6 million/mL, p<0.001). 1, 5

Common Pitfall to Avoid

Do not use the 1 mg daily dose approved for postmenopausal women with breast cancer in male patients. 2, 6, 7 The three-times-weekly 0.5 mg regimen is safer and more appropriate for men on testosterone therapy. 1