2.1  Recommended Dosage

Schistosomiasis The recommended dosage for the treatment of schistosomiasis is 20 mg/kg body weight administered orally three times a day separated by 4 to 6 hours, for 1 day only.

Clonorchiasis and Opisthorchiasis

The recommended dosage for the treatment of clonorchiasis and opisthorchiasis is 25 mg/kg body weight administered orally three times a day separated by 4 to 6 hours for 1 day only.

2.2  Administration

Take tablets with water during meals. Do not chew or keep the tablets (or parts of tablets) in the mouth; the bitter taste may cause gagging or vomiting. To prevent choking in pediatric patients under 6 years of age, the tablets may be crushed or disintegrated and mixed with semi-solid food or liquid. Use crushed or disintegrated tablets within 1 hour of mixing.

Praziquantel 600 mg tablets have three scores which can be split into four segments at the scores. When broken, each of the four segments contains 150 mg of praziquantel so that the dosage can be adjusted to the patient’s body weight. Segments are broken off by pressing the score (notch) with thumbnails. If one-quarter of a tablet is required, this is best achieved by breaking the segment from the outer end.

5.1  Clinical Deterioration

The use of praziquantel 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.

5.2  Central Nervous System (CNS) Effects

Praziquantel can exacerbate central nervous system pathology due to schistosomiasis, paragonimiasis, or Taenia solium cysticercosis. As a general rule, consider whether to administer praziquantel 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.

5.3  Potential Lack of Efficacy During the Acute Phase of Schistosomiasis

Data from two observational cohort studies in patients indicate that treatment with praziquantel 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.

5.4  Cardiac Arrhythmias

Bradycardia, ectopic rhythms, ventricular fibrillation, and AV blocks has been observed with praziquantel administration. Monitor patients with cardiac arrhythmias during treatment.

5.5  Hepatic Impairment in Hepatosplenic Schistosomiasis Patients

Reduced hepatic metabolism of praziquantel results in higher and sustained plasma concentrations of unmetabolized praziquantel in patients with liver impairment [see Clinical Pharmacology (12.3)]. Monitor patients for adverse reactions when administering the recommended dose of praziquantel to hepatosplenic schistosomiasis patients with moderate or severe liver impairment (Child-Pugh Class B or C).

5.6  Concomitant Administration with Strong Cytochrome P450 Inducers

Concomitant administration of strong CYP450 inducers, such as rifampin with praziquantel is contraindicated since therapeutically effective levels of praziquantel may not be achieved. [see Contraindications (4) and Drug Interactions (7.1)].

 In patients receiving rifampin who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be considered. However, if treatment with praziquantel is necessary, discontinue rifampin 4 weeks before administration of praziquantel. Treatment with rifampin can then be restarted one day after completion of praziquantel treatment [see Drug Interactions (7.1, 7.2)].

7.1  CYP450 Inducers

Rifampin

Concomitant administration of rifampin, a strong CYP450 inducer, with praziquantel is contraindicated. In patients receiving rifampin, for example, as part of a combination regimen for the treatment of tuberculosis, alternative drugs for schistosomiasis should be considered. If treatment with praziquantel is necessary, treatment with rifampin should be discontinued 4 weeks before administration of praziquantel. Treatment with rifampin can then be restarted one day after completion of praziquantel treatment. [See Contraindications (4), Warnings and Precautions (5.6) and Clinical Pharmacology (12.3).]

Other CYP 450 Inducers

Concomitant administration of other drugs that are CYP450 inducers, for example, antiepileptic drugs (phenytoin, phenobarbital and carbamazepine), and dexamethasone, may also reduce plasma concentrations of praziquantel. [See Warnings and Precautions (5.6).]

7.2  CYP450 Inhibitors

Concomitant administration of drugs that decrease the activity of drug metabolizing liver enzymes (CYP450 inhibitors), for example, cimetidine, ketoconazole, itraconazole, erythromycin may increase plasma concentrations of praziquantel. In addition, grapefruit juice was also reported to produce a 1.6-fold increase in the Cmax and a 1.9-fold increase in the AUC of praziquantel. The effect of this exposure increase on the therapeutic effect and safety of praziquantel has not been systematically evaluated [see Dosage and Administration (2.2)].

8.1  Pregnancy

Risk Summary

Published studies have not identified an association with praziquantel 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.

Data

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 birth weight, and there were no differences in rates of miscarriage, fetal death and major birth defects between the praziquantel­-treated and control patients. In another randomized controlled trial that included 2,507 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.

8.2  Lactation

Risk Summary

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 mother’s clinical need for praziquantel and any potential adverse effects on the breastfed infant from praziquantel or from the underlying maternal condition.

8.4  Pediatric Use

Safety and dosing recommendations of praziquantel in pediatric patients 1 to 17 years have been established. Safety of praziquantel 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 (6)].

8.5  Geriatric Use

Clinical studies of praziquantel 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 (12.3)].

8.6  Hepatic Impairment

Following oral administration of praziquantel to patients with liver impairment, reduced hepatic metabolism of praziquantel results in higher and sustained plasma concentrations of unmetabolized praziquantel [see Clinical Pharmacology (12.3)]. Monitor patients for adverse reactions when administering the recommended dose of praziquantel to hepatosplenic schistosomiasis patients with moderate or severe liver impairment (Child-Pugh Class B or C).

8.7  Renal Impairment

No dosage adjustment of praziquantel is necessary in patients with renal impairment. Nephrotoxic effects of praziquantel or its metabolites are not known [see Clinical Pharmacology (12.3)].

12.1  Mechanism of Action

Praziquantel is an anthelmintic drug [see Microbiology (12.4)].

12.3  Pharmacokinetics

Absorption

After oral administration, 80% of an administered praziquantel dose is absorbed, with maximal serum concentrations of praziquantel achieved 1 to 3 hours after dosing.

Elimination

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

Metabolism

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

Excretion

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

Specific Populations

Patients with Hepatic Impairment

The pharmacokinetics of praziquantel were studied in 40 patients with Schistosoma mansoni infections with varying degrees of hepatic impairment (See Table 1). In patients with schistosomiasis, the pharmacokinetic parameters did not differ significantly between those with normal hepatic function (Group 1) and those with mild (Child-Pugh class A) hepatic impairment. However, in patients with moderate-to-severe hepatic impairment (Child-Pugh class B and C), praziquantel half-life, Cmax, and AUC increased progressively with the degree of hepatic impairment. In Child-Pugh class B, the increases in mean half-life, Cmax, and AUC relative to Group 1 were 1.58-fold, 1.76-fold, and 3.55-fold, respectively. The corresponding increases in Child-Pugh class C patients were 2.82-fold, 4.29-fold, and 15-fold for half-life, Cmax, and AUC.

Table 1: Pharmacokinetic parameters of praziquantel in four groups of patients with varying degrees of liver function following administration of 40 mg/kg of praziquantel tablets under fasting conditions.

a) p<0.05 compared to Group 1

b) p<0.05 compared to Group 2

c) p<0.05 compared to Group 3

Patients with Renal Impairment

Excretion of praziquantel following oral administration of praziquantel might be delayed in patients with impaired renal function, but accumulation of unchanged drug would not be expected.

Drug Interaction Studies

Rifampin (CYP450 Inducer)

In a crossover study with a 2-week washout period, 10 healthy subjects ingested a single 40 mg/kg oral dose of praziquantel following pre-treatment with oral rifampin (600 mg daily for 5 days). Plasma praziquantel concentrations were undetectable in 7 out of 10 subjects. When a single 40 mg/kg oral dose of praziquantel was administered to these same healthy subjects two weeks after discontinuation of rifampin, the mean praziquantel AUC and Cmax were 23% and 35% lower, respectively, than when praziquantel was given alone.

12.4  Microbiology

Praziquantel induces a rapid contraction of schistosomes by a specific effect on the permeability of the cell membrane. The drug further causes vacuolization and disintegration of the schistosome tegument. However, the mechanism of action is unknown.

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 [see Indications and Usage (1)]. Published in vitro data have shown a potential lack of efficacy of praziquantel against migrating schistosomulae [see Warnings and Precautions (5.3)].

13.1  Carcinogenesis, Mutagenesis, Impairment of Fertility

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).