Frequently (and not so frequently) Asked Questions
BRIEF: What is in the domperidone?
What is in the domperidone, do you know? what is the specific drug that is the key ingredient?
Domperidone is a D2 dopamine receptor antagonist. It works at the receptor level to prevent fescue and ergot alkaloids from inhibiting the release of prolactin. As expensive as it is and given th opportunities for deactivation presented by the whole eating and digestion process, I don't think it is a very good candidate as a feed additive. This is entirely speculation and a suggestion for a researchable subject, not a suggested treatment for your horses (after all, I am not a vet): One might want to stick to an injectible agent to maintain better control of dosages and/or look for a cheaper drug that does not need to be injected very often. An old drug made from the Rauwolfia serpentina plant called reserpine also causes increases in prolactin. It can be taken orally, too. I am not sure of its exact mechanism, but it somehow depletes the body of catecholamines so they are not there to interact with the receptors. Reserpine would not be as specific as domperidone and it has tranquilizing, depressing, hypotensive side effects that might not be desirable in a horse under many circumstances, but if it worked, once a couple of doses are given, you might get by with one or two injections per week. Reserpine may be harmful to the fetus, for all I know, so I would wait for someone to do this in a research setting, or search the literature to see if anyone has tried it previously, before doing this as a managment technique.