PIP: Recently I was asked to give a 3rd medroxyprogesterone injection (Depo-Promone; Upjohn TUCO, Belgium) to a female boxer. The 2 previous occasions the dog had been injected, respectively, in the right and left flank area, with an unknown dose (probably 100 mg). According to the owner, the injections had been given perpendicularly to the skin. About 2 weeks after each injection, an atrophic area developed at the injection site. Though the skin was completely normal, there was an almost round excavation, of about 5 cm diameter and .5 cm depth; most probably this was due to atrophic changes in the subcutaneous tissue (muscle? fat? connective tissue?). 3 weeks after the 3rd injection (100 mg; which was given carefully sc in the axilla area) no atrophic changes had developed (this might exclude atrophic changes in the connective tissue). As no similar cases had been reported to the pharmaceutical company, I tried to reproduce the effect by injecting 50 mg of medroxyprogesterone im in 2 different places of the hind limb muscles of a female sterilized German Shepherd dog. 2 weeks later no changes had occurred. So the origin of the atrophic changes remains unclear. It might be that only certain breeds are susceptible, that certain hormonal conditions have certain influences, that the injection ought to be done into the fat tissue, or that this effect is an extremely rare side effect of the drug. I would be most grateful if colleagues who have had similar experiences would let me know.