Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.

PRAZIQUANTEL

Chemistry - A prazinoisoquinoline derivative anthelmintic, praziquantel occurs as a white topractically white, hygroscopic, bitter tasting, crystalline powder, either odorless or having a faintodor. It is very slightly soluble in water and freely soluble in alcohol.

Storage, Stability, Compatibility

Unless otherwise instructed by the manufacturer, praziquanteltablets should be stored in tight containers at room temperature. Protect from light.

Pharmacology - PRAZIQUANTEL

Praziquantel's exact mechanism of action against cestodes has not been determined. At low concentrations in vitro, the drug appears to impair the function of their suckers andstimulates the worm's motility. At higher concentrations in vitro, praziquantel increases thecontraction (irreversibly at very high concentrations) of the worm's strobilla (chain of proglottids).
Also, praziquantel causes irreversible focal vacuolization with subsequent cestodal disintegration atspecific sites of the cestodal integument.
In schistosomes and trematodes, praziquantel directly kills the parasite, possibly by increasingcalcium ion flux into the worm. Focal vacuolization of the integument follows and the parasite isphagocytized.

Uses, Indications

Praziquantel is indicated for (approved labeling) for the treatment of
Dipylidium caninum, Taenia pisiformis and Echinococcus granulosis in dogs, and Dipylidiumcaninum and Taenia taeniaeformis in cats. Fasting is not required nor is it recommended beforedosing. A single dose is usually effective, but measures should be taken to prevent reinfection, particularly against D. caninum.
Praziquantel has been used in birds and other animals, but it is usually not economically feasibleto use in large animals. In humans, praziquantel is used for schistosomiasis, other trematodes (lung, liver, intestinal flukes) and tapeworms. It is not routinely effective in treating F. hepatica infectionsin humans.

Pharmacokinetics - PRAZIQUANTEL

Praziquantel is rapidly and nearly completely absorbed after oral administration, but there is a significant first-pass effect after oral administration. Peak serum levels areachieved after 30-120 minutes in dogs.
Praziquantel is distributed throughout the body and crosses the blood-brain barrier into the CNSand across the intestinal wall.
Praziquantel is metabolized by the liver to metabolites of unknown activity. It is excreted primarilyin the urine and the elimination half-life is approximately 3 hours in the dog.

Contraindications, Precautions, Reproductive Safety

The manufacturer recommends not using praziquantel in puppies less than 4 weeks old or in kittens less than 6 weeks old. However, acombination product containing praziquantel and febantel from the same manufacturer is approvedfor use in puppies and kittens of all ages. No other contraindications are listed for this compoundby the manufacturer. In humans, praziquantel is contraindicated in patients hypersensitive to thedrug. Praziquantel is considered to be safe to use in pregnant dogs or cats.

Adverse Effects, Warnings

When used orally, praziquantel can cause anorexia, vomiting, lethargy or diarrhea in dogs, but the incidence of these effects is less than 5%. In cats, adverse effects were quite rare (<2%) in field trials using oral praziquantel with salivation and diarrhea beingreported.
An increased incidence of adverse effects have been reported after using the injectable product. Indogs, pain at the injection site, vomiting, drowsiness and/or a staggering gait were reported fromfield trials with the drug. Some cats (9.4%) showed symptoms of diarrhea, weakness, vomiting, salivation, sleepiness, transient anorexia and/or pain at the injection site.

Overdosage, Acute Toxicity

Praziquantel has a wide margin of safety. In rats and mice the oral
LD50 is at least 2 g/kg. An oral LD50 could not be determined in dogs, as at doses greater than 200mg/kg, the drug induced vomiting. Parenteral doses of 50 - 100 mg/kg in cats caused transientataxia and depression. Injected doses at 200 mg/kg were lethal in cats.

Drug Interactions

Reportedly in humans, synergistic activity occurs with praziquantel and oxamniquine in the treatment of schistosomiasis. The clinical implications of this synergism inveterinary patients is not clear.

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