Use
Testolactone, 13-hydroxy-3-oxo-13,17-secoandrosta-1,4-dien-17-oic acidΔ-lactone (Teslac),was originally synthesized as a possible anabolic steroid,considering its structural similarity to testosterone. The keystructural difference from anabolic steroids is the D-ring lactone instead of the typical cyclopentyl ring. Althoughconsidered in many texts an androgen or anabolic steroid (itis a Schedule III drug because of its classification as an anabolicsteroid), testolactone lacks androgenic effects in vivo.Its action is believed to be caused by irreversible inhibitionof aromatase. It is a relatively weak inhibitor of aromatase,but the irreversible nature of the inhibition can lead to prolongedeffects. Its relatively weak inhibition of aromataseand its undesirable dosage schedule (5×50-mg tabletsq.i.d.) give this older agent only limited use in breast cancertreatment because of better available options.