Praziquantel: Uses, Interactions, Mechanism of ... - DrugBank

Praziquantel: Uses, Interactions, Mechanism of ... - DrugBank

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Praziquantel is a pyrazino-isoquinolein derivative from the thioxantonic group used as a broad anthelmintic spectrum. Specifically, it is known as a treatment of trematodes and cestodes infections such as schistosomiasis, taeniasis, and cysticercosis. 5 The efficacy of praziquantel in treating parasitic flatworms infection with low cost (~US$0.20 drug cost to treat a child) makes it an integral to WHO's plan to eliminate schistosomiasis by . 6 , 7 Despite being approved since , the exact mechanism of action is yet to be elucidated. 7

Praziquantel is an anthelmintic medication used to treat parasitic worm infections such as schistosomiasis, clonorchiasis, and opisthorchiasis

Indication

Associated Conditions

Indication TypeIndicationCombined Product DetailsApproval LevelAge GroupPatient CharacteristicsDose FormTreatment ofClonorchiasis&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;Treatment ofOpisthorchiasis&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;Treatment ofOpisthorchiasis&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;Treatment ofSchistosomiasis&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;Treatment ofSchistosomiasis&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;&#;

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Contraindications & Blackbox Warnings

Pharmacodynamics

In vitro studies on trematodes and cestodes have shown that praziquantel induces a rapid contraction of schistosomas by a specific effect on the permeability of the cell membrane. The drug further causes vacuolization and disintegration of the schistosome tegument. The effect is more marked on adult worms compared to young worms. An increased Ca2+-influx may play an important role.9

Secondary effects are inhibition of glucose uptake, lowering of glycogen levels and stimulation of lactate release. The action of praziquantel is specific to trematodes and cestodes; nematodes (including filariae) are not affected.9

Praziquantel is active against schistosoma (for example, Schistosoma mekongi, Schistosoma japonicum, Schistosoma mansoni and Schistosoma hematobium), and infections due to the liver flukes, Clonorchis sinensis/Opisthorchis viverrini. Published in vitro data have shown a potential lack of efficacy of praziquantel against migrating schistosomulae.10

An interesting quirk of praziquantel is that it is relatively ineffective against juvenile schistosomes. While initially effective, effectiveness against schistosomes decreases until it reaches a minimum at 3-4 weeks. Effectiveness then increases again until it is once again fully effective at 6-7 weeks.1

Mechanism of action

Although the exact mechanism of action is unknown, praziquantel was hypothesized to target the β subunits of voltage-gated Ca2+ channels, particularly in Schistosoma mansoni and Schistosoma japonicum, due to the lack of two conserved serine residues in these subunits. This is supported by the finding that co-administration of calcium channel blockers like nicarpidine and nifedipine renders 50% of Schistosoma mansoni resistant to praziquantel.10,1

Increased exposure of antigens on the worm surface was also observed, but little research has been done to elucidate on the mechanism of action.1

TargetActionsOrganism

A

Schistosome calcium ion (Ca2+) channels

other/unknown

Schistosoma

Absorption

After oral administration of praziquantel, about 80% of the dose is absorbed. In subjects with normal hepatic function who received 40 mg/kg of praziquantel under fasting conditions, the mean ± SD Cmax and AUC were 0.83 ± 0.52 µg/mL and 3.02 ± 0.59 µg/mL x hr. The Tmax was 1.48 ± 0.74 hours.10

Volume of distribution

Following a single oral dose of 40 mg/kg of praziquantel in healthy volunteers, the volume of distribution was estimated to be ± L.4

Protein binding

Approximately 80% of praziquantel is bound exclusively to albumin.3

Metabolism

Praziquantel is rapidly metabolized by the cytochrome P450 enzyme system and undergoes a first-pass effect after oral administration.10

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• Praziquantel

  • 4&#;hydroxy praziquantel

Route of elimination

Approximately 80% of an oral dose of praziquantel is excreted in the kidneys, almost exclusively (greater than 99%) in the form of praziquantel metabolites.10

Half-life

Following oral administration, the elimination half-life of praziquantel in serum ranges between 0.8 to 1.5 hours.10

Clearance

Following a single oral dose of 40 mg/kg of praziquantel in healthy volunteers, the clearance was estimated to be 11.4 ± 2.8 L/kg/h.4

Adverse Effects

Toxicity

The acute toxicity of praziquantel is relatively low, as demonstrated by oral LD50 values ranging between 200 - mg/kg in various species.9

Published studies have not identified an association between praziquantel use during pregnancy and major birth defects, miscarriage, or adverse maternal or fetal outcomes. In animal reproduction studies conducted in pregnant rats and rabbits no adverse developmental outcomes were observed with oral administration of praziquantel during organogenesis at approximately 0.65 times (rats) or 1.3 times (rabbits) the highest recommended human daily dose of 75 mg/kg/day, based on body surface area.10

Mutagenicity studies of praziquantel published in the scientific literature are inconclusive. Long-term oral carcinogenicity studies in rats and golden hamsters did not reveal any carcinogenic effect at doses up to 250 mg/kg/day (about half of the human daily dose based on body surface area). Praziquantel had no effect on fertility and general reproductive performance of male and female rats when given at oral doses ranging from 30 to 300 mg/kg body weight (up to 0.65 times the human daily dose based on body surface area).10

Pathways

Not Available

Pharmacogenomic Effects/ADRs

Not Available

PRAZIQUANTEL