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→Pharmacokinetics
* These drugs are excreted very slowly and so the plasma concentration curve has a very long tail.
* These drugs are excreted very slowly and so the plasma concentration curve has a very long tail.
* The initial peak will kill all adult worms and the residual "tail" is able to have a high enough concentration to ensure that infective larvae ingested, for a time after treatment, are incapable of establishing. This provides a '''period of protection against reinfection'''.
* Pour on products are available but these are unable to provide the initial adulticide peak but will provide a period of protection for an even greater period of time.
* These prolonged protection periods mean that these drugs are often used in prophylactic worm control programmes for cattle. They can be '''prophylactic''' and be given at spring turnout to prevent eggs and infective larvae accumulating on the pasture.
They can be '''metaphylactic''' and be given mid-season, thus protecting animals grazing on contaminated pastures.
* Due to this long tail on the plasma curve, the product remains in the animal's body longer than most. This means that its meat and milk withdrawal periods are longer than other anthelmintics. Eprinomectin is the exception is used in dairy cows as it isn't excreted in milk.
==Safety==
==Safety==