What is/are Praziquantel?
Praziquantel (Biltricide) is an anthelmintic effective against flatworms. Praziquantel is not licensed for use in humans in the UK; it is, however, available as a veterinary anthelmintic, and is available for use in humans on a named-patient basis.
Praziquantel is used to treat diseases in humans, mammals, and fish that are caused by infection with several types of internal/ gastrointestinal, and external parasites including the following:
- Salmon poisoning disease
- Hydatid disease caused by infection of various organs with larval stages of tapeworms of the genus Echinococcus
- Cysticercosis caused by infection of the brain and/ or muscles with the eggs and larvae of the pork tapeworm Taenia solium (though it has been judged less effective than albendazole in treatment of neurocysticercosis)
- Feline taeniasis caused in cats by gastrointestinal infection with adult tapeworms of the species Taenia taeniaeformis; used either alone or in combination with pyrantel pamoate
- Toxocariasis in cats and dogs whose gut is infected with the roundworms/ nematodes Toxocara cati or Toxocara canis respectively; use is often combined with pyrantel
- Schistosomiasis caused by trematodes of the genus Schistosoma. As of 2005, praziquantel is the primary treatment for human schistosomiasis, for which it is usually effective in a single dose.
- Clonorchiasis brought on by the Chinese liver fluke Clonorchis sinensis
- Paragonimiasis caused by infection with lung flukes, mostly of the species Paragonimus westermani.
- Fasciolopsiasis caused by intestinal fluke Fasciolopsis buski
- Diplozoon paradoxum and other Trematoda infections of many fish species.
The majority of side effects develop due to the release of the contents of the parasites as they are killed and the consequent host immune reaction. The heavier the parasite burden, the heavier and more frequent the side effects normally are.
- Central nervous system: Frequently occurring side effects are dizziness, headache, and malaise. Drowsiness, somnolence, fatigue, and vertigo have also been seen. Almost all patients with cerebral cysticercosis experience CNS side effects related to the cell-death of the parasites (headache, worsening of pre-existing neurological problems, seizures, arachnoiditis, and meningism). These side effects may be life-threatening and can be reduced by coadministration of corticosteroids. It is strongly recommended that all patients with cerebral cysticercosis are hospitalized during treatment.
- GI Tract: Approximately 90% of all patients have abdominal pain or cramps with or without nausea and vomiting. Diarrhea may develop and may be severe with colic. Sweating, fever, and sometimes bloody stools may occur together with diarrhea.
- Liver: Asymptomatic and transient increases of liver enzymes (AST and ALT) are noted frequently (up to 27%). No case of symptomatic liver damage has ever been seen so far.
- Sensitivity reactions: Urticaria, rash, pruritus and eosinophilia in white blood cell counts
- Other locations/body as a whole: Lower back pain, myalgia, arthralgia, fever, sweating, various cardiac arrhythmias, and hypotension
Mechanism of action
Although the mode of action is not exactly known at present, there is experimental evidence that praziquantel increases the permeability of the membranes of schistosome cells towards calcium ions. The drug thereby induces contraction of the parasites, resulting in paralysis in the contracted state. The dying parasites are dislodged from their site of action in the host organism and may enter systemic circulation or may be destroyed by host immune reaction (phagocytosis). Additional mechanisms including focal disintegrations and disturbances of oviposition (laying of eggs) are seen in other types of sensitive parasites.
Another hypothesis concerning the mechanism of action of praziquantel has been recently reported. The drug seems to interfere with adenosine uptake in cultured worms. This effect may have therapeutical relevance given that the schistosome, as the taenia and the echinococcus (other praziquantel sensitive parasites), is unable to synthesize purines such as adenosine de novo.
Bayer's Animal Health Division website states, "Praziquantel is active against cestodes (tapeworms). Praziquantel is absorbed, metabolized in the liver and excreted in the bile. Upon entering the digestive tract from the bile, cestocidal activity is exhibited. Following exposure to praziquantel, the tapeworm loses its ability to resist digestion by the mammalian host. Because of this, whole tapeworms, including the scolices (plural of "scolex"), are very rarely passed after administration of praziquantel. In many instances only disintegrated and partially digested pieces of tapeworms will be seen in the stool. The majority of tapeworms are digested and are not found in the feces."
Praziquantel is administered as a racemate, but only the (R)-enantiomer is biologically active; the enantiomers may be separated using a resolution of an amine obtained from praziquantel.
This article uses material from the Wikipedia article Praziquantel, which is released under the Creative Commons Attribution-Share-Alike License 3.0.