I don't know if that is how you spell it, but it is a injection that you give to help with the marishness. My friend is getting a horse that is(might) be on it, and does that mean she is getting a insane horse?
I know a few horses that have been on it (apparently it helps geldings be less sour as well...). It doesn't necessarily mean her horse is crazy, but there is something that is undesirable enough in her actions that someone thought to put her on it. It doesn't work with every horse but if it helps her horse, great.
It's a human birth control shot designed for once a month with low doses of hormones to prevent pregnancy. I imagine it would act the same way with horses depending on the dosage and very well my curb some of the "pms" problems mares tend to have just like their human counterparts. Other than that I'm clueless as to why a horse would be receiving the injections