Infections from relatively large organisms such as worms can often require treatment with special pharmaceutical drugs. A class of drugs known as the benzimidazole family is one such therapy. This worm medicine is not usually used with humans, but is instead sometimes given as a treatment to domestic animals, which are generally more likely than humans to contract worms.
Several different drugs make up this class of pharmaceuticals, such as mebendazole and flubendazole, along with benzimidazole itself. Generally, most of this family of compounds are effective in treating infections from both roundworms, called nematodes, and flatworms, called trematodes. A few, such as netobimin, can also treat liver flukes. These drugs tend to be the most effective at treating infections in horses and ruminants, such as cows. Worm infections in other species, such as dogs, cats, birds, and even humans, may sometimes be treated with a benzimidazole drug, however.
Benzimidazole and its relatives all treat worm infections in the same way. These drugs attach to a part of the worm's cell structure known as microtubules, preventing them from growing. Building microtubules is necessary for cell growth and division, and they can disintegrate without constant growth. Therefore, this type of worm medication prevents worms from growing or reproducing, and eventually directly kill the worm. This class of drug can also kill some types of fungus through the same mechanism.
Certain properties of benzimidazole drugs affect how they are used in treatment. Most of them are not very water soluble, which means they must be given in a paste or suspension form. Additionally, they absorb into the body at a slow rate, and some are broken down, or metabolized, by various tissues of the body fairly quickly. Repeated dosing at 12 hour intervals may sometimes be used to work around these issues. Alternately, controlled release forms of these medications may sometimes be used for the same reason.
Benzimidazole drugs are quite effective, but their usage may be declining. Some areas of the world, such as India, have seen cases where worms were resistant to this type of treatment. Other drugs have also been developed that are more water soluble and lack the metabolism issues that benzimidazole and its derivatives have, as well. Despite these drawbacks, however, these drugs remain the first treatment choice for many types of parasitic infections because they are effective against such a broad range of worms.