Fui

Roundworm (A. lumbricoides), pinworms (Ā£. vermicularis)

Praziquantel (Biltricide)

All 3 Schistosoma speciesĀ®

Pyrantel (pamoate)" (Antiminth)

Roundworm (A. lumbricoides) and pinworm (E. vermicularis)

Pyrivinium pamoate' (Povan)

Pinworm (E. Vermicularis) Threadworm (Strongyloides stercoralis)

Table 7-10. (Continued)

Drug"

Structure"

Disease (organism)

Stibocaptate'' (Astiban)

Nr i

Schistosomiasis, all three species

Suramin1 (Germanin)

River blindness (O. olvulus)

Tetrachlorethylene (Nema)

Thiabendazole (Mintezol)

Hookworm (Necator americanus), liver and intestinal flukes (F. hepatica, F. buski)

Threadworm (S. stercoralis); pinworm (E. vermicularis)h

" Trade name in parentheses.

b Number in parentheses indicates where structure can be found.

c Very water-insoluble drug, either itself or as a sait such as hydroxynaphthoate or pamoate.

d Available in the United States only through CDC, UPHS.

* Not available in the United States.

1 There are several other benzimidazole carbamates under investigation that vary the 6-substituent: p-F-C6H5CO, flubendazole, cyclopropyl carbonyl, ciclobendazole, and CH3CH2CH2-S-, albendazole.

g Investigational against Fasciola spp. and other flukes.

h Investigational in trichinosis (Trichinella spiralis).

' Not yet approved in the United States.

' Now approved as an immunostimulant in cancer chemotherapy.

uptake by the gonads of the male affecting spermatogenesis. There is also a loss of glycogen in the organism. This has been shown to be due to the potentiation of schistosomal, but not mammalian, glycogen phosphorylase by inhibiting phosphorylase phosphatase, the enzyme that catalyzes the inactivation of phosphorylase. Whether this has a contributing effect toward worm death is not clear. The increased wasteful utilization of glucose possibly produces a form of "malnutrition." As with the previously considered nitroheterocy-cles, the nitro group seems essential, and the drug appears activated by its reduction.

Metrifonate, which was originally introduced as an organic phosphate insecticide, is a pro-drug for dichlorovos,10 a potent acetylcholinesterase inhibitor (Chapter 8) to which it is nonenzymatically metabolized spontaneously in vitro even at neutral pH (Eq. 7.11). The drug's clinical application is exclusively against S. hematobium infections. Although some effectiveness against other schistosomes exists, this is not achieved at safe doses.

10 Dichlorovos is a commercial ectoparasitizide for veterinary use and against household pet pests.

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