Frequently (and not so frequently) Asked Questions
BRIEF: What is in the domperidone?
QUESTION:
What is in the domperidone, do you know? what is the specific drug that is the key
ingredient?
ANSWER:
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.