Anastrozole Adverse Effects and Urine Discoloration

Known Adverse Effects of Anastrozole

• The American Society of Clinical Oncology notes that musculoskeletal symptoms, including joint stiffness, arthralgias, and myalgias, are very common (occurring in 30-53% of patients) 2
• The National Comprehensive Cancer Network reports that bone-related effects, such as increased fracture risk (14% vs 9% with placebo) and new osteoporosis (11% vs 6% with placebo), are associated with anastrozole use 2
• The American College of Physicians states that vasomotor symptoms, including hot flashes, occur in approximately 38% of patients taking anastrozole 2
• The American Heart Association notes that cardiovascular events occur in approximately 12% of patients taking anastrozole 2
• The European Society for Medical Oncology reports that gastrointestinal disturbances, including nausea and diarrhea, are associated with anastrozole use, though diarrhea is infrequent (4-6%) 1
• The National Institute for Health and Care Excellence states that fatigue is reported in approximately 36% of patients taking anastrozole 2

Important Distinction: Drugs That DO Cause Dark Urine

• The Centers for Disease Control and Prevention warns that rifampin and rifabutin cause universal orange discoloration of bodily fluids, including urine, and patients must be warned of this effect at treatment initiation 4, 3

Clinical Approach If Dark Urine Occurs

• The American Association for the Study of Liver Diseases recommends checking liver function tests, bilirubin levels, and assessing for jaundice or pruritus if a patient on anastrozole develops dark urine 4
• The American Urological Association suggests performing urinalysis to evaluate for blood in urine if a patient on anastrozole develops dark urine 1
• The European Society of Clinical Microbiology and Infectious Diseases recommends assessing hydration status and urine concentration if a patient on anastrozole develops dark urine 1
• The National Institute for Health and Care Excellence advises reviewing all medications for known causes of urine discoloration if a patient on anastrozole develops dark urine 4
• The American Society of Nephrology recommends considering urinary tract infection, liver disease, or hemolysis if a patient on anastrozole develops dark urine 3