Niclosamide (9.122), a salicylamide derivative, is the drug of choice for most tape-
worm infestations. Niclosamide inhibits oxidative phosphorylation within the parasite,
causing the cestode to be rapidly killed.
Oxamniquine (9.123), a semisynthetic tetrahydroquinoline, is the treatment of choice
forSchistosoma mansoni infections. Its mechanism of action is unknown but appears
to entail binding of the drug to the nematode’s DNA, somehow causing its death.
Alternatively, it may cause worm paralysis and expulsion.
Praziquantel (9.124), a synthetic isoquinoline–pyrazine derivative, is effective for the
treatment of schistosome infections; it is also effective against trematode and cestode
infestations. This agent increases membrane permeability to Ca^2 +in the nematode,
causing paralysis, dislodgement, and death of the worm.
Pyrantel pamoate (9.125), a tetrahydropyrimidine derivative, is a broad-spectrum
antihelminthic active against pinworm and hookworm. This drug causes release of
acetylcholine in the worm, producing stimulation and paralysis, leading to expulsion
from the host’s intestinal tract.
590 MEDICINAL CHEMISTRY