PRAZIQUANTEL - Par Health USA, LLC

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

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 bodyweight. 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.

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.

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.

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.

Bradycardia, ectopic rhythms, ventricular fibrillation, and AV blocks has been observed with praziquantel 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 (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).

Strong Cytochrome P450 3A Enzyme (CYP 3A) Inducers

Concomitant administration of strong CYP 3A inducers, such as rifampin, with praziquantel is contraindicated since therapeutically effective levels of praziquantel are unlikely to be achieved. [see Contraindications (4), Drug Interactions (7.1) and Clinical Pharmacology (12.3)].

Moderate CYP 3A Inducers

 Avoid concomitant administration of praziquantel 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 praziquantel. [see Drug Interactions (7.1)].

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 praziquantel is necessary immediately, increase monitoring for reduced anthelmintic efficacy associated with praziquantel [see Drug Interactions (7.1)].

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 praziquantel 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 praziquantel treatment, if needed [see Drug Interactions (7.1)]

Strong and Moderate CYP 3A Inducers

Concomitant administration of praziquantel with Strong and Moderate CYP 3A inducers decrease praziquantel AUC and C_max  [see Clinical Pharmacology (12.3)] which may reduce the efficacy of praziquantel. Concomitant administration of a Strong CYP 3A inducer, such as rifampin, with praziquantel is contraindicated [see Contraindications (4)]. Concomitant administration of a Moderate CYP 3A inducer, such as efavirenz, should be avoided unless the benefit outweighs the risks 

[see Warnings and Precautions (5.6) and Clinical Pharmacology (12.3).]

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

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 birthweight, 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.

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.

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)].

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)].

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).

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)].

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

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, C_max, and AUC increased progressively with the degree of hepatic impairment. In Child-Pugh class B, the increases in mean half-life, C_max, 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, C_max, 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 (Strong CYP 3A 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 C_max were 23% and 35% lower, respectively, then when praziquantel was given alone.

Efavirenz (Moderate CYP 3A Inducer)

In a crossover study, 20 healthy subjects ingested a single 40 mg/kg oral dose of praziquantel following pretreatment with oral efavirenz (400 mg daily for 13 days). Oral efavirenz reduced the mean praziquantel AUC and C_max by 77% (95% confidence interval: 38% to 91%) and 79% (95% confidence interval: 41% to 92%), respectively, when coadministered with praziquantel compared to praziquantel given alone.

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)].

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).