Danazol: prolonged suppression of gonadotropins after subcutaneous administration in the castrate male rat

Effect of particle size on the prolonged action of subcutaneous danazol in male and female rats

OBJECTIVE

To investigate the effects of two different particle sizes of danazol in male and female rats.

DESIGN

Prospective, vehicle-controlled study.

SETTING

Undergraduate college research facility and medical research laboratory.

ANIMALS

18 castrated male rats and 18 cycling female rats.

INTERVENTION(S)

Preparations of danazol with particle sizes of 2.05 microm or 5.2 microm were administered as a single subcutaneous injection of 400 mg/kg to castrated male rats or estrus-cycling females.

MAIN OUTCOME MEASURE(S)

Serum LH level in males and estrous cycle length in females.

RESULT(S)

In males, both preparations significantly (P<. 001) suppressed serum LH by day 5 of treatment. Gonadotropin levels remained low throughout the 35-day study in rats that received the larger-particle danazol, whereas LH levels began to increase after 25 days in rats that received smaller-particle danazol. In females, the normal 4- to 5-day estrous cycle interval was prolonged to 38.7 days (P<.001) in those that received the larger-particle danazol and 25.5 days in those that received the smaller-particle danazol.

CONCLUSION(S)

The results demonstrate the prolonged effectiveness of a single subcutaneous dose of danazol and indicate that one might be able to predict the effective duration of activity by changing the particle size of the danazol administered.