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Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of parasitic worm infections in mammals, birds, amphibians, reptiles, and fish.[3] In humans specifically, it is used to treat schistosomiasis, clonorchiasis, opisthorchiasis, tapeworm infections, cysticercosis, echinococcosis, paragonimiasis, fasciolopsiasis, and fasciolosis.[3] It should not be used for worm infections of the eye.[4] It is taken by mouth.[3]
Side effects in humans may include poor coordination, abdominal pain, vomiting, headache, and allergic reactions.[4] While it may be used during pregnancy, it is not recommended for use during breastfeeding.[4] Praziquantel is in the anthelmintic class of medications.[3] It works partly by affecting the function of the worm's sucker.[3]
Praziquantel was approved for medical use in the United States in .[3] It is on the World Health Organization's List of Essential Medicines.[5]
Medical uses
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Praziquantel is used to treat diseases caused by infection with several types of internal/gastrointestinal, and external parasites, including:
Side effects
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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.[citation needed]
Pregnancy
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The WHO states praziquantel is safe during pregnancy.[22] Animal studies have failed to reveal evidence of fetal harm. Praziquantel is effective in reducing schistosomiasis during pregnancy.[23] Another trial found that treatment with praziquantel did not increase the rates of low birthweight, fetal death, or congenital anomalies.[24]
Drug interactions
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The antibiotic rifampicin decreases plasma concentrations of praziquantel.[25]
Carbamazepine and phenytoin are reported to reduce the bioavailability of praziquantel.[26] Chloroquine also reduces its bioavailability.[27]
The drug cimetidine heightens praziquantel bioavailability.[28][29]
Mechanism of action
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The drug's mode of action is not exactly known at present, but experimental evidence indicates praziquantel increases the permeability of the membranes of schistosome cells towards calcium ions. The drug thereby induces contraction of the parasites' muscle, 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.[citation needed]
Another hypothesis regarding the mechanism of action is that it interferes with adenosine uptake in worms.[30] 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.[citation needed]
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."[31]
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.[32]
Pharmacokinetics
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Praziquantel is well absorbed (about 80%) from the gastrointestinal tract. However, due to extensive first-pass metabolism, only a relatively small amount enters systemic circulation. Praziquantel has a serum half-life of 0.8 to 1.5 hours in adults with normal renal and liver function. Metabolites have a half-life of 4 to 5 hours. In patients with significantly impaired liver function (Child-Pugh score B and C), the serum half-life is increased to 3 to 8 hours. Praziquantel and its metabolites are mainly excreted renally; within 24 h after a single oral dose, 70 to 80% is found in urine, but less than 0.1% as the unchanged drug. Praziquantel is metabolized through the cytochrome P450 pathway via CYP3A4. Agents that induce or inhibit CYP3A4 such as phenytoin, rifampin, and azole antifungals will affect the metabolism of praziquantel.[citation needed]
Praziquantel has a particularly dramatic effect on patients with schistosomiasis. Studies of those treated have shown that within six months of receiving a dose of praziquantel, up to 90% of the damage done to internal organs due to schistosomiasis infection can be reversed.[14]
History
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Praziquantel was developed in the laboratories for parasitological research of Bayer AG and Merck KGaA in Germany (Elberfeld and Darmstadt) in the mid-s.[citation needed]
Society and culture
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Brand names
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Regulatory approval
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Praziquantel is on the World Health Organization's List of Essential Medicines.[5]
Praziquantel is not licensed for use in humans in the UK, but it can be imported when necessary on a named-patient basis.[34] It is available in the UK as a veterinary anthelmintic.
Praziquantel is FDA approved in the US for the treatment of schistosomiasis and liver flukes, although it is effective in other infections.[35]
Veterinary medicine
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It may cause problems in dogs with MDR1 mutations.[37]
See also
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References
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Included as part of the PRECAUTIONS section.
The use of Biltricide in patients with schistosomiasis may be associated with clinical deterioration (for example, paradoxical reactions, serum sickness Jarisch-Herxheimer like reactions: sudden inflammatory immune response suspected to be caused by the release of schistosomal antigens). These reactions predominantly occur in patients treated during the acute phase of schistosomiasis. They may lead to potentially life-threatening events, for example, respiratory failure, encephalopathy, papilledema, and/or cerebral vasculitis.
Biltricide can exacerbate central nervous system pathology due to schistosomiasis, paragonimiasis, or Taenia solium cysticercosis. As a general rule, consider whether to administer Biltricide to individuals reporting a history of epilepsy and/or other signs of potential central nervous systems involvement such as subcutaneous nodules suggestive of cysticercosis unless the potential benefit justifies the potential risk. Hospitalize the patient for duration of treatment when schistosomiasis or fluke infection is found to be associated with cerebral cysticercosis.
Data from two observational cohort studies in patients indicate that treatment with Biltricide in the acute phase of infection may not prevent progression from asymptomatic infection to acute schistosomiasis, or from asymptomatic infection/acute schistosomiasis into chronic phase.
Bradycardia, ectopic rhythms, ventricular fibrillation, and AV blocks has been observed with Biltricide administration. Monitor patients with cardiac arrhythmias during treatment.
Reduced hepatic metabolism of praziquantel results in higher and sustained plasma concentrations of unmetabolized praziquantel in patients with liver impairment [see CLINICAL PHARMACOLOGY]. Monitor patients for adverse reactions when administering the recommended dose of Biltricide to hepatosplenic schistosomiasis patients with moderate or severe liver impairment (Child-Pugh Class B or C).
Concomitant administration of strong CYP 3A inducers, such as rifampin, with Biltricide is contraindicated since therapeutically effective levels of praziquantel are unlikely to be achieved. [see CONTRAINDICATIONS, DRUG INTERACTIONS, and CLINICAL PHARMACOLOGY].
Avoid concomitant administration of Biltricide with moderate CYP 3A inducers, such as efavirenz, due to risk of a clinically significant decrease in praziquantel plasma concentrations which may lead to reduced therapeutic effect of Biltricide. [see DRUG INTERACTIONS].
In patients receiving a clinically significant CYP 3A inducer drug who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be considered, where possible. If Biltricide is necessary immediately, increase monitoring for reduced anthelmintic efficacy associated with Biltricide [see DRUG INTERACTIONS].
In patients receiving a clinically significant CYP 3A inducer drug whose treatment could be delayed, discontinue the CYP 3A inducer drug at least 2 weeks to 4 weeks before administration of Biltricide and, where possible, consider starting alternative medications that are not CYP 3A inducers. The CYP 3A inducer drug can be restarted one day after completion of Biltricide treatment, if needed [see DRUG INTERACTIONS]
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).
Published studies have not identified an association with Biltricide use during pregnancy and major birth defects, miscarriage or adverse maternal or fetal outcomes (see Data). 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.
The estimated background risk of major birth defects and miscarriage for the indicated population are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Human Data
Two randomized controlled clinical trials have been conducted using praziquantel for the treatment of schistosoma infection in pregnant women. In one randomized controlled trial in pregnant women with schistosoma (S. japonicum) infection, 186 pregnant women were treated with praziquantel compared to 184 women who received placebo. Treatment with praziquantel during pregnancy had no effect on birthweight, and there were no differences in rates of miscarriage, fetal death and major birth defects between the praziquantelÂtreated and control patients. In another randomized controlled trial that included pregnant women in Uganda, 18% of women were infected with schistosoma infection. Treatment with praziquantel during pregnancy had no effect on mean birth weight, perinatal mortality or major birth defects.
In other published studies, including a retrospective observational study, case series and case reports, there have been no reports of major birth defects, stillbirths or other adverse pregnancy outcomes associated with the use of praziquantel during pregnancy.
Animal Data
No evidence of fetal harm was observed in rats and rabbits at praziquantel dose levels of 30 to 300 mg/kg body weight given repeatedly by oral administration during the period of organogenesis. These doses were up to 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.
Limited data from published literature reports the presence of praziquantel in human milk at low concentrations. There is no information on the effects of praziquantel in the breastfed infant or effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the motherâ&#;&#;s clinical need for Biltricide and any potential adverse effects on the breastfed infant from Biltricide or from the underlying maternal condition.
Safety and dosing recommendations of Biltricide in pediatric patients 1 to 17 years have been established. Safety of Biltricide in pediatric patients younger than 1 year of age has not been established.
Post-marketing experience and published literature indicates that pediatric patients 1 to 17 years of age treated with praziquantel experience similar adverse reactions as adults treated with praziquantel [see ADVERSE REACTIONS].
Clinical studies of Biltricide did not include a sufficient number of subjects ages 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older patients cannot be ruled out. This drug is known to be substantially excreted by the kidney. Because elderly patients are more likely to have decreased renal function, the risk of toxic reactions to this drug may be greater in these patients [see CLINICAL PHARMACOLOGY].
Following oral administration of Biltricide to patients with liver impairment, reduced hepatic metabolism of praziquantel results in higher and sustained plasma concentrations of unmetabolized praziquantel [see CLINICAL PHARMACOLOGY]. Monitor patients for adverse reactions when administering the recommended dose of Biltricide to hepatosplenic schistosomiasis patients with moderate or severe liver impairment (Child-Pugh Class B or C).
No dosage adjustment of Biltricide is necessary in patients with renal impairment. Nephrotoxic effects of Biltricide or its metabolites are not known [see CLINICAL PHARMACOLOGY].
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