Oral administration of an anti-inflammatory does not compromise the efficacy of intra-testicular injection of zinc gluconate as a contraceptive for dogs

The objective was to determine whether the efficacy of zinc gluconate (Testoblock(?)) as a chemical contraceptive in male dogs was compromised in the presence of metamizole sodium (a nonsteroidal antiinflammatory/analgesic agent). Ten sexually mature mongrel dogs were assigned to two groups, a control group (n = 5) and a treated group (n = 5). Testoblock(?), a proprietary zinc-gluconate (13.1 mg zinc/ml) solution in a physiological vehicle, was injected into each testis (0.2-1.0 ml/testis, based on testis width). Half of the dogs (treated group) were also given metamizole sodium (also known as sodium dipyrone) orally (25mg/kg three times a day for 2 days), starting 2-3 h after testis injection. A physical examination and assessment of testis width, hematology, clinical chemistry (hepatic and renal function) and semen characteristics, were done immediately after treatment and then every 2 months for 180 days. There was no post-treatment scrotal biting or licking, although there was transient testicular swelling in both control and treated dogs during the first 3 days after injection. At 60 days after injection, all dogs were azoospermic. At 120 and 180 days, seven dogs had azoospermia and the remaining three (two control and one treated) had apparent aspermia (no ejaculate could be collected). There were no significant differences between groups for clinical findings or any aspect of hematology, renal, or hepatic function. In conclusion, giving metamizole sodium concurrent with an intra-testicular injection of a zinc-based solution did not interfere with chemical sterilization and it improved animal welfare.