It is recommended that the cattle injectable formulation of moxidectin (recently approved by FDA) be used in goats because moxidectin has a superior pharmacokinetic profile in goats when administered by subcutaneous injection as compared to when administered orally.
This means that a much greater proportion of the drug administered remains in the body at high therapeutic levels, but is no more persistent over time. Therefore, worm resistance to moxidectin will develop more slowly if given by injection to goats. Because the drug reaches high therapeutic levels when injected, there is no need to double the dose.
So when administering moxidectin by subcutaneous injection, use the cattle dose which is on the label (0.09 mg/lb; 0.2 mg/kg; 21 day meat withdrawal ) This is the one exception with goats where a dewormer should be administered orally and where the regular label dose (not 2 times the dose) should be used.
However, it is still OK to administer moxidectin orally to goats (just not preferred). But if an individual has a personal preference to administer moxidectin orally to goats, then the sheep oral drench at a 2X dose (0.18 mg/lb; 0.4 mg/kg) should be given.
Source: Southern Consortium for Small Ruminant Parasite Control (SCSRPC) - wormx.org
**No formulation of moxidectin is FDA-approved for use in goats. If a animal drug is not used in accordance with its label, its use requires veterinary approval.