Local injection of a sustained-release antiandrogen formulation into a target prostatic site: an experimental study

To evaluate the efficacy of one intraprostatic injection with sustained-release chlormadinone acetate (CMA-SR) in rats.

CMA, a steroidal antiandrogen, was enclosed in microcapsules for sustained-release (CMA-SR). Forty-eight rats were divided into group A (intraprostatic CMA-SR 8 mg/kg, one injection), group B (as A but with 25 mg/kg), group C (intraprostatic, vehicle only) and group D (subcutaneous, s.c., CMA 10 mg/kg once daily for 4 weeks). Prostate weight, body weight and plasma testosterone levels were measured for up to 4 weeks.

After a s.c. injection with CMA-SR, residual CMA at the s.c. injection site decreased with time. The injected prostate lobe weighed significantly (P < 0.05) less than the contralateral lobe in groups A and B, and significantly (P < 0.05) less in groups A and B than in group C. Both prostate lobes in group D were significantly (P < 0.05) smaller than in group C (P < 0.05). Plasma testosterone levels were significantly lower in group D than in group C (P < 0.05).

The sustained release of CMA after one intraprostatic injection persistently decreased the weight of the target prostate. This new concept of antiandrogen therapy might therefore be effective in man, with fewer systemic adverse reactions.