Anthelmintic (cestodes and trematodes)
Praziquantel is an antiparasitic medicine used to treat schistosomiasis and liver fluke infections (clonorchiasis and opisthorchiasis). It is taken orally, usually as a single dose or short course calculated by weight. It is well tolerated; the most common side effects are headache, dizziness and abdominal discomfort.
Also known as: Biltricide
Combining Praziquantel with Ritonavir increases Praziquantel concentrations, with an increased risk of adverse effects, especially of the central nervous system.
Praziquantel is rapidly metabolised by the cytochrome P450 enzyme system (CYP3A4) and undergoes first-pass effect; the praziquantel label explicitly states that "CYP450 inhibitors, for example cimetidine, ketoconazole, itraconazole, erythromycin and ritonavir, may increase praziquantel plasma concentrations". Raised levels potentiate the adverse effects (headache, dizziness, abdominal discomfort, nausea, urticaria and, in susceptible patients, seizures or arrhythmias — bradycardia, ventricular fibrillation and AV blocks have been observed). Monitor the patient during treatment (usually 1 day of therapy) and consider a lower dose in patients with liver disease, where exposure is already increased.
Praziquantel + ritonavir: ritonavir inhibits CYP3A4 and raises praziquantel levels. Watch for adverse effects (headache, dizziness, seizures).
As a CYP3A4 inhibitor, Ritonavir reduces Praziquantel metabolism, increasing its exposure and the risk of toxicity (headache, dizziness, seizures).
Watch for CNS adverse effects (headache, dizziness, drowsiness, seizures).
Seizures or severe neurological effects require discontinuation and evaluation.
Monitor adverse effects and consider reducing the Praziquantel dose if the combination is necessary.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9 ; approved Ritonavir label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2849298e-de6e-47bb-8194-56e075b33fc3 — with additional reference: Prontuário Terapêutico do INFARMED, INFARMED (11th ed., 2012)
The combination of Praziquantel with Efavirenz is not recommended: it significantly reduces Praziquantel concentrations, with a risk of therapeutic failure.
Praziquantel is metabolised by CYP3A4 and efavirenz is a moderate CYP3A4 inducer: the praziquantel label documents the study with 20 volunteers in which efavirenz (400 mg/day for 13 days) reduced the mean praziquantel AUC by 77% (95% CI: 38–91%) and Cmax by 79% (95% CI: 41–92%), and classifies the combination as "avoid, unless the benefit outweighs the risks, due to the risk of a clinically significant decrease in praziquantel plasma concentrations which may lead to reduced therapeutic effect". If treatment cannot be delayed, consider stopping efavirenz 2–4 weeks before praziquantel (if possible) and monitor the anthelmintic efficacy; in practice, prefer an efavirenz alternative or another anthelmintic.
Efavirenz + praziquantel: efavirenz induces CYP3A4 and greatly reduces praziquantel levels (AUC −77%). Avoid; monitor efficacy.
Efavirenz, a moderate CYP3A4 inducer, accelerates the hepatic metabolism of Praziquantel, lowering its exposure.
Monitor the parasitological response and symptoms of the infection.
Treatment failure requires a therapeutic alternative.
Prefer an alternative; if unavoidable, closely monitor the parasitological response.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9 ; approved Efavirenz label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=92603fa5-7a2c-4bfb-9a70-aadb4fba952c — with additional reference: Prontuário Terapêutico do INFARMED, INFARMED (11th ed., 2012)
The combination of Praziquantel with Rifampin is contraindicated: Rifampin markedly reduces Praziquantel concentrations, posing a risk of therapeutic failure.
Praziquantel undergoes extensive CYP3A4 first-pass metabolism; rifampicin, a potent inducer, markedly reduces its concentrations and compromises efficacy against schistosomiasis, taeniasis and other parasitoses — a classically label-documented interaction. Avoid the coadministration; if unavoidable, treat the parasitosis after completing the rifampicin regimen or choose an alternative therapy.
Praziquantel + rifampicin: rifampicin markedly reduces praziquantel levels (CYP3A4 induction), with antiparasitic treatment failure. Avoid the combination.
Rifampin, a strong CYP3A4 inducer, increases the hepatic metabolism of Praziquantel, significantly reducing its exposure.
Monitor the parasitological response (e.g. egg clearance) when the combination is unavoidable.
Persisting parasitosis despite treatment suggests failure and requires an alternative strategy.
Do not co-administer; complete Rifampin treatment before starting Praziquantel or choose an alternative antiparasitic treatment.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9 ; approved Rifampin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b389b1a3-672f-47e3-916c-4a9c044b211b — with additional reference: Prontuário Terapêutico do INFARMED, INFARMED (11th ed., 2012)
Grapefruit juice inhibits CYP3A4 and can raise praziquantel concentrations and its adverse effects.
Avoid grapefruit juice during treatment.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9
A high-fat meal increases praziquantel absorption; taking it during or after a meal is recommended.
Take during or immediately after a meal.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9
Praziquantel is extensively metabolised in the liver; severe hepatic impairment raises active drug concentrations.
Use with caution and consider dose reduction in severe liver disease.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9
Praziquantel can cause headache, dizziness and, in neurocysticercosis, seizures, especially in patients with epilepsy.
Use with caution in patients with epilepsy and monitor neurological symptoms.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9
Data on praziquantel in pregnancy are limited; WHO guidelines allow its use in helminth infections when indicated.
May be used in any trimester per WHO guidelines for helminthiasis.
Present in breast milk in small amounts; generally compatible.
No specific contraception required.
DailyMed/FDA (NIH/NLM) — approved Praziquantel label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=34ce1cdd-648e-4f1e-8512-bf3d4cc22eb9
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Praziquantel induces rapid contraction of schistosomes by a specific effect on parasite cell membrane permeability, followed by vacuolization and disintegration of the tegument; exposure of parasite antigens facilitates the host immune response.
The exact mechanism of action is not fully known: it increases parasite membrane permeability to calcium, causing spastic contraction and tegument damage. Active against Schistosoma spp. and liver flukes (Clonorchis sinensis/Opisthorchis viverrini).
After oral administration about 80% of the dose is absorbed, with peak serum concentrations 1-3 hours after dosing. In patients with moderate-to-severe hepatic impairment (Child-Pugh B/C), Cmax and AUC increase progressively (up to 4.3-fold and 15-fold in Child-Pugh C).
Rapidly metabolised by the cytochrome P450 enzyme system (CYP3A4), with a first-pass effect after oral administration; about 80% of an oral dose is excreted by the kidneys, almost exclusively (>99%) as metabolites.
Serum elimination half-life of 0.8 to 1.5 hours after oral administration (increases in liver disease: ~4.7 h in Child-Pugh B and ~8.5 h in Child-Pugh C).
