Chemistry - A prazinoisoquinoline derivative anthelmintic, praziquantel occurs as a white to practically white, hygroscopic, bitter tasting, crystalline powder, either odorless or having a faint odor. It is very slightly soluble in water and freely soluble in alcohol.
Storage/Stability/Compatibility - Unless otherwise instructed by the manufacturer, praziquantel tablets should be stored in tight containers at room temperature. Protect from light.
Pharmacology - 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 and stimulates the worm’s motility. At higher concentrations in vitro, praziquantel increases the contraction (irreversibly at very high concentrations) of the worm’s strobilla (chain of proglottids). Also, praziquantel causes irreversible focal vacuolization with subsequent cestodal disintegration at specific sites of the cestodal integument.
In schistosomes and trematodes, praziquantel directly kills the parasite, possibly by increasing calcium ion flux into the worm. Focal vacuolization of the integument follows and the parasite is phagocytized.
Uses/Indications - Praziquantel is indicated for (approved labeling) for the treatment of Dipylidium caninum, Taenia pisiformis and Echinococcus granulosis in dogs, and Dipylidium caninum and Taenia taeniaeformis in cats. Fasting is not required nor is it recommended before dosing. 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 feasible to 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 infections in humans.
Pharmacokinetics - Praziquantel is rapidly and nearly completely absorbed after oral administration, but there is a significant first-pass effect after oral administration. Peak serum levels are achieved after 30-120 minutes in dogs.
Praziquantel is distributed throughout the body and crosses the blood-brain barrier into the CNS and across the intestinal wall.
Praziquantel is metabolized by the liver to metabolites of unknown activity. It is excreted primarily in 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, a combination product containing praziquantel and febantel from the same manufacturer is approved for use in puppies and kittens of all ages. No other contraindications are listed for this compound by the manufacturer. In humans, praziquantel is contraindicated in patients hypersensitive to the drug. 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 being reported.
An increased incidence of adverse effects have been reported after using the injectable product. In dogs, pain at the injection site, vomiting, drowsiness and/or a staggering gait were reported from field 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 200 mg/kg, the drug induced vomiting. Parenteral doses of 50 - 100 mg/kg in cats caused transient ataxia 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 in veterinary patients is not clear.
Sheep & Goats:
For all species of Moniezia, Stilesia, or Avitellina:
a) 10 - 15 mg/kg (Roberson 1988a)
For susceptible parasites:
a) 5 mg/kg PO. (Fowler 1989)
a) 2.5-4.0 mg/kg orally for cestodiasis (Chandresekharan, 2002), (Chandresekharan et.al. 1995).
Chandrasekharan,K. 2002. Specific diseases of Asian elephants.
Journal of Indian Veterinary Association Kerala 7:(3):31-34
a) Chandrasekharan,K., Radhakrishnan,K., Cheeran,J.V., Nair,K.N.M., and Prabhakaran,T., 1995. Review of the Incidence, Etiology and Control of Common Diseases of Asian Elephants with Special Reference to Kerala. In: Daniel,J.C. (Editor), A Week with Elephants; Proceedings of the International Seminar on Asian Elephants. Bombay Natural History Society; Oxford University Press, Bombay, India pp. 439-449
Monitoring Parameters -
1) Clinical efficacy
Client Information - Fasting is not required nor is it recommended before dosing. A single dose is usually effective, but measures should be taken to prevent reinfection, particularly against D. caninum. Tablets may be crushed or mixed with food. Because tapeworms are often digested, worm fragments may not be seen in the feces after using.
Dosage Forms/Preparations/FDA Approval Status/Withholding Times -
Praziquantel 23 mg (feline), 34 mg (canine) Tablets; Droncit® Tablets (Bayer); (Rx) Approved for use in cats and dogs.
Praziquantel Injection 56.8 mg/ml in 10 ml vials; Droncit® Injection (Bayer); (Rx) Approved for use in cats and dogs.
Praziquantel/pyrantel pamoate; Drontal Tablets® (Bayer) (Rx) Approved for use in cats
Praziquantel/pyrantel pamoate plus febantel; Drontal Plus Tablets® (Bayer) (Rx) small, medium and large dog sizes
Praziquantel Tablets 600 mg; Biltricide® (Bayer) (Rx)
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