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

Abstract

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.

Androgens and estrogens in benign prostatic hyperplasia: Past, present and future

“…In a study of seven beagles with spontaneous BPH, treatment with the SERM Tamoxifen resulted in decreased prostate volume [165]. A randomized trial of Tamoxifen in dogs with BPH showed an average 28.5% decrease in prostate volume compared to placebo [198]. SERMs are well-tolerated in men, and have been shown to ameliorate side effects of androgen ablation therapy in men with metastatic prostate cancer, reduce fracture risk and improve lipid profiles [199, 200].…”

Pharmacological Treatment for Common Prostatic Conditions in Dogs – Benign Prostatic Hyperplasia and Prostatitis: an Update

“…In another study, tamoxifen was administered for 60 days (2.5–10 mg/day) to 6 dogs with normal prostate glands and 8 dogs presenting BPH (Gonzalez et al. ). At the end of the treatment, the prostatic volume had decreased by 28.5 ± 4.3% in BPH males.…”

“…No clinical or haematological side effects were observed during 4 weeks of post-treatment follow-up (Corrada et al 2004). In another study, tamoxifen was administered for 60 days (2.5-10 mg/day) to 6 dogs with normal prostate glands and 8 dogs presenting BPH (Gonzalez et al 2009). At the end of the treatment, the prostatic volume had decreased by 28.5 AE 4.3% in BPH males.…”

“…No side effects were observed regarding haematological and biochemical parameters. On the whole, anastrozole was assessed as a safe and effective alternative for the medical management of canine BPH (Gonzalez et al 2009). However, the relatively short treatment period for both drugs should be indicated.…”

“…Another antioestrogen, the aromatase inhibitor anastrozole, has been comparatively investigated for BPH treatment (Gonzalez et al. ), showing similar effects. After 60‐day oral administration (0.25–1 mg/day), the prostate gland volume was reduced by 21.6 ± 6.3% with a subsequent progressive re‐increase within the 4‐month follow‐up period.…”