Comparison of the Effect of the Aromatase Inhibitor, Anastrazole, to the Antioestrogen, Tamoxifen Citrate, on Canine Prostate and Semen

This study compared the efficiency of the aromatase inhibitor, anastrazole, with the antioestrogenic receptor blocker, tamoxifen, on normal (NRL) and hyperplastic prostate glands. Forty healthy dogs were classified as NRL (n = 18) or abnormal (ABN) with benign prostate hyperplasia (n = 22). The dogs were randomly assigned to one of the following six groups, treated for 60 days; oral placebo for normal (NRL-PLC; n = 6) and abnormal (ABN-PLC; n = 6), oral anastrazole 0.25–1 mg/day, for normal (NRL-ANZ, n = 6) and abnormal (ABN-ANZ, n = 8) and oral tamoxifen citrate 2.5–10 mg/day for normal (NRL-TMX; n = 6) and abnormal (ABN-TMX; n = 8) dogs. The dogs were evaluated before treatment and then monthly for 4 months. At the end of the treatment, the prostatic volume decreased by 28.5 ± 4.3%, 21.6 ± 6.3% and 0.7 ± 1.0% in the ABN-TMX, ABN-ANZ and ABN-PLC (p < 0.01), respectively. From then on, prostatic volume began to increase without reaching pre-treatment values at the end of the study. In the ABN animals, there were no differences for this parameter between ANZ and TMX treatment (p > 0.1), whereas in the NRL animals ANZ produced a less pronounced decrease (p < 0.05), libido, testicular consistency and scrotal diameter decreased during treatment in the TMX group (p > 0.05). These parameters and sperm volume, count, motility and morphological abnormalities remained unaltered throughout the study in the ANZ and PLC groups (p > 0.05). There were no haematological nor biochemical side effects. Anastrazole might offer a safe and effective alternative for the medical management of dogs with benign prostatic hyperplasia.