The 8-hydroxyquinolines are a group of synthetic compounds with antibacterial, antifungal, and antiprotozoal activity. The best-known compounds of this class are iodochlorhydroxyquin (clioquinol), diiodohydroxyquin (iodoquinol), broxyquinoline, and hydroxyquinoline. Because they are not absorbed from the GI tract to any degree, their main use has been to treat intestinal infections caused by bacteria or protozoa (such as Giardia). Hydroxyquinolines are also used topically for skin infections caused by bacteria and fungi. Hydroxyquinolines are potentially neurotoxic when used for prolonged periods. The dose for a 455-kg horse is 10 g/day, PO, using a decreasing dosage regimen to discontinue medication.