Macrocyclic Lactones
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This group of drugs are derived from Streptomyces species and are coded as 3-AV products. They are commonly known as avermectins and milbemycins. Drugs in use include; ivermectin, abamectin, doramectin, moxidectin, eprinomectin and selamectin.
Activity
- They have a wide spectrum of activity. They are endectocides; active against common nematodes at all developmental stages and against many arthropods.
- They are inactive against trematodes, cestodes and adult filarial worms. Though are active against migrating heart worm larvae and are used as heartworm prophylactics in cats and dogs.
- Their mode of action is by opening invertebrate specific glutamate-gated chloride channels on the post-synaptic membranes. This results in flaccid paralysis of the parasite.
Pharmacokinetics
- These drugs are excreted very slowly and so the plasma concentration curve has a very long tail.