No drugs are specifically approved for microfilaricidal treatment of ''Dirofilaria immitis'', and successful elimination of adult worms should result in the demise of circulating microfilariae four to six weeks later<sup>2</sup>. Single doses of ivermectin, milbemycin oxime, moxidection or selamectin are, however, effective at removing microfilariae from the circulation. The sudden death of large numbers of microfilariae may invoke an anaphylactic response, and oral prednisolone may be administered with microfilaricides to help prevent this. | No drugs are specifically approved for microfilaricidal treatment of ''Dirofilaria immitis'', and successful elimination of adult worms should result in the demise of circulating microfilariae four to six weeks later<sup>2</sup>. Single doses of ivermectin, milbemycin oxime, moxidection or selamectin are, however, effective at removing microfilariae from the circulation. The sudden death of large numbers of microfilariae may invoke an anaphylactic response, and oral prednisolone may be administered with microfilaricides to help prevent this. |