Monday Pharmaceutical Mystery: October 14

Why is a 15-year-old boy being prescribed anastrozole?

Among the usual pharmacy chaos, your technician is searching for a prescription for a pediatric patient. After looking everywhere, you find the printed electronic prescription in your endless stack of doctor calls to make.

The prescription is for anastrozole (Arimidex, ANI Pharmaceuticals) 1 mg po daily, and you were certain this drug was selected in error. From what you recall, anastrozole is an aromatase inhibitor used in postmenopausal women for the treatment of breast cancer.

You explain to the patient’s mother that you will call the doctor to clarify the prescription right away; you figure the doctor accidentally clicked on the wrong drug. The patient’s mother tells you that her 15-year-old son is indeed supposed to be taking anastrozole for growth.

Mystery: Why is anastrozole used in children for growth?

Solution: Although data is limited, anastrozole (or letrozole) has been used and has been/is being studied off-label in an attempt to increase growth in boys with idiopathic short stature (ISS). It is possible that giving an aromatase inhibitor in conjunction with growth hormone to adolescents with ISS in late puberty may increase adult height, more than growth hormone alone.

REFERENCE

Rothenbuhler, A, et al. A randomized pilot trial of growth hormone with anastrozole versus growth hormone alone, starting at the very end of puberty in adolescents with idiopathic short stature. Int J Pediatr Endocrinol. 2015; 2015(1): 4. Published online 2015 Feb 16. doi: 10.1186/1687-9856-2015-4