Pediatric Schistosomiasis Medication

Updated: Feb 26, 2015
  • Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: Russell W Steele, MD  more...
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Medication

Medication Summary

Praziquantel (a pyrazinoquinolone) has become the main antischistosomal agent because it is effective against all human pathogens and is well tolerated orally. Other oral compounds available are oxamniquine (a nitroquinolone that is no longer available in the United States) and metrifonate (an organophosphorus cholinesterase inhibitor that is also unavailable in the United States), but these have limited parasite specificity.

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Anthelmintics

Class Summary

Parasite biochemical pathways are different from those of the human host; thus, toxicity is directed to the parasite, egg, or larvae. The mechanism of action varies within the drug class. Antiparasitic actions may include the following:

- Inhibition of microtubules, causing irreversible block of glucose uptake

- Tubulin polymerization inhibition

- Depolarizing neuromuscular blockade

- Cholinesterase inhibition

- Increased cell membrane permeability, resulting in intracellular calcium loss

- Vacuolization of the schistosome tegument

- Increased cell membrane permeability to chloride ions via chloride-channel alteration

Praziquantel (Biltricide)

Animal studies report that praziquantel induces rapid contraction of schistosomes by exerting a specific effect on the permeability of the cell membrane. The drug further causes vacuolization and disintegration of the schistosomal tegument. It has a more marked effect on adult worms than on young worms. After oral administration, praziquantel is rapidly absorbed (80%). It is subject to a first-pass effect and extensive metabolism.

Oxamniquine

Oxamniquine is no longer available in the United States. It is active only against S mansoni. Oxamniquine is effective in disintegrating the schistosome tegument to which phagocytes attach, causing death.

The drug is well absorbed and is metabolized extensively to inactive metabolites that, in turn, are excreted in urine. The plasma half-life is approximately 1-2.5 hours, and a peak in drug concentrations is usually reached in 1-1.5 hours after oral administration.

Metrifonate

Metrifonate, an organophosphate derivative with anthelmintic and anticholinesterase activity, is not available in the United States. It is used as an alternative to praziquantel for treatment of S haematobium infections; it is not effective for S japonicum or S mansoni infections. The drug is well absorbed from the gastrointestinal (GI) tract, with peak levels occurring 1 hour after administration.

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