Praziquantel
Mechanism :
Praziquantel induces a rapid contraction of schistosomes by a specific effect on the permeability of the cell membrane and causes vacuolization and disintegration of the schistosome tegument. The effect is more marked on adult worms compared to young worms. Secondary effects are inhibition of glucose uptake, lowering of glycogen levels and stimulation of lactate release. The action of praziquantel is limited very specifically to trematodes and cestodes; nematodes (including filariae) are not affected.
Indication :
- Schistosomiasis
- Liver fluke (off-label)
- Lung fluke (off-label)
- Intestinal fluke
- Neurocysticercosis (off-label)
- Echinococcosis
Contraindications :
Patients who have previously shown hypersensitivity to the drug. Since parasite destruction within the eye may cause irreparable lesions, ocular cysticercosis should not be treated with praziquantel.
Dosing :
<4 years, safety and efficacy not established.
Schistosomiasis:
≥4 years:
20 mg/kg (Oral) thrice a day for 1 day to be taken at intervals of 4-6 hours.
Clonorchiasis, Opisthorchiasis:
≥4 years:
75 mg/kg/day (Oral) in 3 divided doses for 1 day at intervals of 4-6 hours.
Cysticercosis (off-label):
≥4 years:
50-100 mg/kg/day (Oral) in 3 divided doses for 30 days.
Flukes (off-label):
≥4 years:
75 mg/kg/day in 3 daily divided doses for 1-2 days.
Tapeworms (off-label):
≥4 years:
5-10 mg/kg as a single dose or 25 mg/kg for hymenolepsis nana.
Adverse Effect :
Adverse reactions vary according to dose and duration of praziquantel medication. Abdominal pain, nausea, vomiting, headache, vertigo, weakness, dizziness, drowsiness, malaise, myalgia, urticaria or elevated temperature may occur occasionally/frequently. Mild increases in liver enzymes have been reported in some patients.
Interaction :
Dexamethasone: Can lead to lower concentrations of praziquantel in blood.
Phenytoin, Carbamazepine, Phenobarbital: may reduce serum levels of praziquantel.
Chloroquine: Reduces bioavailability of praziquantel.
Cimetidine: Hepatic enzyme inhibitor - may increase serum levels of praziquantel.
Alcohol: Potentiates CNS effects of praziquantel.
Hepatic Dose :
Increased plasma concentration of unmetabolized drug are seen in moderate to severe hepatic impairment due to reduced clearance by the liver. Therefore dose reduction would be reasonable and levels of drug should be monitored.