Praziquantel (praziquantel)

Dosage adjustments are not necessary in patients with renal impairment.

Praziquantel is administered orally. The tablets should not be chewed but can be halved or quartered to allow administration of individualized doses. Patients should be instructed to immediately swallow the praziquantel tablets, halves, and/or quarters with a sufficient amount of water during meals. Retention of the tablets or tablet segments in the mouth may cause gagging or vomiting as a result of the drug's bitter taste. Some clinicians state that regurgitation during administration of the tablets may theoretically predispose the patient to the development of cysticercosis during therapy for Taenia solium+ infections.

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Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Praziquantel/Dexamethasone

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Dexamethasone may induce the metabolism of praziquantel by CYP3A4.(1-3)

CLINICAL EFFECTS: Concurrent or recent use of dexamethasone may decrease the levels and effectiveness of praziquantel.

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The concurrent use of praziquantel and strong inducers of CYP3A4, such as dexamethasone, is contraindicated.(1) In patients receiving dexamethasone who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be used. If praziquantel is required, increase monitoring for praziquantel efficacy. If schistosomiasis treatment can be delayed, discontinue dexamethasone at least 2 to 4 weeks before administration of praziquantel. Dexamethasone therapy may be resumed 1 day after completion of praziquantel therapy.(1)

DISCUSSION: In a study in eight subjects, concurrent dexamethasone decreased praziquantel levels by 50%.(3)

Praziquantel/Rifampin; Rifapentine

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Rifampin and rifapentine may induce the metabolism of praziquantel by CYP3A4.(1)

CLINICAL EFFECTS: Concurrent or recent use of rifampin or rifapentine may decrease the levels and effectiveness of praziquantel.(1,2)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The concurrent use of praziquantel and rifampin or rifapentine is contraindicated.(1) In patients receiving rifampin or rifapentine who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be used. If praziquantel is required, increase monitoring for praziquantel efficacy. If schistosomiasis treatment can be delayed, discontinue rifampin or rifapentine at least 2 to 4 weeks before administration of praziquantel. Rifampin or rifapentine therapy may be resumed 1 day after completion of praziquantel therapy.(1)

DISCUSSION: In an open, randomized, cross-over study in 10 healthy Thai males, pretreatment with rifampin (600 mg daily for 5 days) decreased the levels of a single oral dose of praziquantel (40 mg/kg) to undetectable levels in 7 of 10 subjects. In the 3 subjects with detectable levels, the maximum concentration (Cmax) and area-under-curve (AUC) of praziquantel were decreased by 81% and 85%, respectively. In the same subjects, pretreatment with rifampin (600 mg daily for 5 days) decreased the levels of praziquantel (3 doses of 40 mg/kg, 8 hours apart) to undetectable levels in 5 of 10 subjects. In the 5 subjects with detectable levels, Cmax and AUC of praziquantel were decreased by 74% and 80%, respectively.(2)

Praziquantel/Selected Strong Cyp3a4 Inducers

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Strong CYP3A4 inducers may induce the metabolism of praziquantel by CYP3A4.(1)

CLINICAL EFFECTS: Concurrent or recent use of a strong CYP3A4 inducer may decrease the levels and effectiveness of praziquantel.

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The concurrent use of praziquantel and strong inducers of CYP3A4 is contraindicated.(1) In patients receiving strong CYP3A4 inducers who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be used. If praziquantel is required, increase monitoring for praziquantel efficacy. If schistosomiasis treatment can be delayed, discontinue strong CYP3A4 inducers at least 2 to 4 weeks before administration of praziquantel. The inducer may be resumed 1 day after completion of praziquantel therapy.(1)

DISCUSSION: A study examined praziquantel levels in 10 healthy controls, 10 subjects maintained on phenytoin monotherapy, and 10 subjects maintained on carbamazepine monotherapy. Praziquantel area-under-curve (AUC) and maximum concentration (Cmax) were reduced by 90.3% and by 92.1%, respectively, in carbamazepine-treated subjects when compared to control subjects. Praziquantel AUC and Cmax were reduced by 74% and 76%, respectively, in phenytoin-treated subjects when compared to control subjects.(2) Strong CYP3A4 inducers linked to this monograph include: apalutamide, barbiturates, carbamazepine, encorafenib, enzalutamide, fosphenytoin, ivosidenib, lumacaftor, mitotane, phenobarbital, phenytoin, primidone, and St. John's Wort.(3)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Praziquantel/Chloroquine

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: How chloroquine decreases praziquantel levels is unknown.(1)

CLINICAL EFFECTS: Concurrent use of chloroquine may result in decreased levels and effectiveness of praziquantel.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving concurrent therapy with chloroquine may need higher doses of praziquantel.(2) Monitor patients for praziquantel therapy failure.

DISCUSSION: In a study in 8 healthy male subjects, administration of chloroquine (600 mg) with praziquantel (40 mg/kg) decreased the maximum concentration (Cmax) and area-under-curve (AUC) of praziquantel by 58.7% and 64.5%, respectively, when compared to the administration of praziquantel alone in the same subjects. There was large inter-patient variability and one patient did not have any change in praziquantel levels.(2)

Praziquantel/Moderate Cyp3a4 Inducers

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Moderate inducers of CYP3A4 may induce the metabolism of praziquantel.(1,2)

CLINICAL EFFECTS: Concurrent or recent use of a moderate inducer of CYP3A4 may decrease the levels and effectiveness of praziquantel.(1,2)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The US manufacturer of praziquantel recommends avoiding concomitant administration with moderate CYP3A4 inducers due to the risk of a clinically significant decrease in praziquantel plasma concentration which may lead to reduced therapeutic effect of praziquantel.(2) In patients receiving a clinically significant CYP3A4 inducer drug who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be considered, where possible. If praziquantel treatment is necessary immediately, increase monitoring for reduced anthelmintic efficacy associated with praziquantel, when used in combination with a moderate CYP3A4 inducer.(2) In patients receiving a clinically significant CYP3A4 inducer drug whose treatment could be delayed, discontinue the CYP3A4 inducer drug at least 2 to 4 weeks before administration of praziquantel and, where possible, consider starting alternative medications that are not CYP3A4 inducers. The CYP3A4 inducer drug can be restarted 1 day after completion of praziquantel treatment, if needed.(2)

DISCUSSION: In a crossover study, 20 healthy subjects ingested a single 40 mg/kg oral dose of praziquantel following pre-treatment with oral efavirenz (400 mg daily for 13 days). Oral efavirenz reduced the mean praziquantel area-under-curve (AUC) by 77% and maximum concentration (Cmax) by 79%, when coadministered with praziquantel compared to praziquantel given alone.(2) Moderate CYP3A4 inducers include: belzutifan, bosentan, cenobamate, dabrafenib, dipyrone, efavirenz, elagolix, etravirine, fexinidazole, lesinurad, lorlatinib, mavacamten, mitapivat, modafinil, nafcillin, pacritinib, pexidartinib, repotrectinib, rifabutin, sotorasib, telotristat, thioridazine, and tovorafenib.(3-4)

There are no moderate interactions for this drug.

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• Ocular cysticercosis

There are no severe contraindications for this drug.

• Severe hepatic disease

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Rare or Very Rare

• Anaphylaxis
• Bloody diarrhea
• Bradycardia
• Cardiac arrhythmia
• Cerebral vasculitis
• Hepatitis
• Hypersensitivity drug reaction
• Interstitial pneumonitis
• Jarisch-herxheimer reaction
• Papilledema
• Polyserositis
• Seizure disorder
• Serum sickness
• Stevens-johnson syndrome
• Ventricular fibrillation

More Frequent

• Abdominal pain with cramps
• Anorexia
• Dizziness
• Drowsy
• Fever
• Headache disorder
• Malaise
• Nausea
• Vomiting

Less Frequent

• Pruritus of skin

Rare or Very Rare

• Dyspnea
• Eosinophilia
• Gait abnormality
• General weakness
• Intention tremor
• Myalgia
• Skin rash
• Tinnitus
• Tremor
• Urticaria
• Vertigo
• Visual changes
• Wheezing

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Reproduction studies in rats and rabbits using praziquantel dosages up to 40 times the usual human dosage have not revealed evidence of harm to the fetus. An increase in the rate of spontaneous abortion occurred in rats following administration of praziquantel dosages 3 times the usual human dosage. There are no adequate and controlled studies to date using praziquantel in pregnant women, and the drug should be used during pregnancy only when clearly needed.

Since praziquantel is distributed into milk, women should temporarily discontinue nursing on the day of praziquantel therapy and for 72 hours after administration of the last dose of the drug.

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