Pyrantel is an anti-helminthic drug developed by Pfizer in the 1960s to treat roundworm, pinworm, hookworm, and other parasitic infections. It works by activating nicotinic cholinergic receptors in the worm's nervous system, causing paralysis and expulsion. Pyrantel is a light yellow to tan powder that is odorless, tasteless, and stable in heat but decomposes in light. It has a chemical formula of C11H14N2S and is administered orally to treat parasitic infections. Common side effects include nausea, diarrhea, dizziness, and headache.