Anthelmintics, dosage

Although the actions of anthelmintic drugs vary, Hieir prime purpose is to kill the parasite Adverse reactions associated with the anthelmintic drugs, if Hiey do occur, are usually mild when the drug is used in Hie recommended dosage. 

Follow the dosage schedule exactly as printed on the prescription container. (See Administering an Anthelmintic Drug for the directions specific for each drug.) It is absolutely necessary to follow the directions for taking the drug to eradicate the helminth. 

The important anthelmintic agents along with their specific uses and dosage are listed in table 9.10.1. 

Dosage of anthelmintics, which usually refers to a single dose, is based on semiquantitative assessment of clinical efficacy, although, when appropriate, bioavailability and the plasma concentration profile of the active moiety (parent drug and/or active... 

When absorption takes place rapidly, which is usual for conventional dosage forms, fca > kd, but when absorption takes place slowly and ka < k(j the flip-flop phenomenon occurs, whereby the rate of absorption controls the rate of elimination of the drug. This situation applies not only to sustained-release oral dosage forms administered to dogs, but also to phenylbutazone and meclofe-namic acid in horses, salicylate administered as an aspirin bolus to cattle and oral suspensions of benzimidazole anthelmintics in ruminant species. 

Importantly, such absolute arbitrary categorization actually affords no useful and gainful objective as a host of anthelamintics have been recognized that particularly manifest both actions equally, as per the strength of dosages employed. Therefore, in a broader sense and perspective the anthelmintics are defined more appropriately as— drugs used to combat any type of helminthiasis . 

Some of the antimalarials , discussed in Chapter-20, are also used as anthelmintics at different dosage regimen. 

These pharmacokinetic interactions are established, and are likely to be clinically important when these anthelmintics are used to treat systemic worm infections. For these infections it may be necessary to increase the albendazole or mebendazole dosage in patients taking phenytoin, carbamazepine or phenobarbital. Monitor the outcome of concurrent use. The interactions are of no importance when these anthelmintics are used for intestinal worm infections (where their action is a local effect on the worms in the gut), which is the most common use of mebendazole in particular. 

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