effective in the treatment of schistosome infections of all species and most
other trematode and cestode infections, including cysticercosis. The drug’s
safety and effectiveness as a single oral dose have also made it useful in mass
treatment of sev-eral infections.
is a synthetic isoquinoline-pyrazine derivative. It is rapidly absorbed, with a
bioavailability of about 80% after oral administration. Peak serum concentrations
are reached 1–3 hours after a therapeutic dose. Cerebrospinal fluid
concentrations of prazi-quantel reach 14–20% of the drug’s plasma
concentration. About 80% of the drug is bound to plasma proteins. Most of the
drug is rapidly metabolized to inactive mono- and polyhydroxylated prod-ucts
after a first pass in the liver. The half-life is 0.8–1.5 hours. Excretion is
mainly via the kidneys (60–80%) and bile (15–35%). Plasma concentrations of
praziquantel increase when the drug is taken with a high-carbohydrate meal or
with cimetidine; bioavail-ability is markedly reduced with some antiepileptics
(phenytoin, carbamazepine) or with corticosteroids.
to increase the permeability of trematode and cestode cell membranes to
calcium, resulting in paralysis, dislodgement, and death. In schistosome
infections of experimen-tal animals, praziquantel is effective against adult
worms and immature stages, and it has a prophylactic effect against cercarial
are taken with liquid after a meal; they should be swallowed without chewing
because their bitter taste can induce retching and vomiting.
Praziquantel is the
drug of choice for all forms of schistosomiasis. The dosage is 20 mg/kg per dose
for two (S mansoni and S haema-tobium) or three (S japonicum and S mekongi) doses at intervals of4–6 hours. High cure rates
(75–95%) are achieved when patients are evaluated at 3–6 months; there is
marked reduction in egg counts in those not cured. The drug is effective in
adults and children and is generally well tolerated by patients in the
hepatos-plenic stage of advanced disease. There is no standard regimen for
acute schistosomiasis (Katayama syndrome), but standard doses as described
above, often with corticosteroids to limit inflammation from the acute immune
response and dying worms, are recom-mended. Increasing evidence indicates rare S mansoni drug resis-tance, which may be
countered with extended courses of therapy (eg, 3–6 days at standard dosing) or
treatment with oxamniquine. Effectiveness of praziquantel for chemoprophylaxis
has not been established.
Standard dosing is 25
mg/kg three times daily for 2 days for each of these fluke infections.
single dose of praziquantel, 5–10 mg/kg, results in nearly 100% cure rates for T saginata, T solium, and D latum
infections. Because praziquantel does not kill eggs, it is theoretically
possible that larvae of T solium
released from eggs in the large bowel could penetrate the intestinal wall and
give rise to cysticercosis, but this hazard is probably minimal.
Albendazole is now the
preferred drug, but when it is not appropri-ate or available, praziquantel has
similar efficacy. Indications for praziquantel are similar to those for
albendazole. The praziquantel dosage is 100 mg/kg/d in three divided doses for
1 day, then 50 mg/ kg/d to complete a 2- to 4-week course. Clinical responses
to ther-apy vary from dramatic improvements of seizures and other neuro-logic
findings to no response and even progression of the disease. Praziquantel—but
not albendazole—has diminished bioavailabilitywhen taken concurrently with a
corticosteroid. Recommendations on use of both antihelminthics and
corticosteroids in neurocysticer-cosis vary.
Praziquantel is the
drug of choice for H nana infections
and the first drug to be highly effective. A single dose of 25 mg/kg is taken
initially and repeated in 1 week.
In hydatid disease,
praziquantel kills protoscoleces but does not affect the germinal membrane.
Praziquantel is being evaluated as an adjunct with albendazole pre- and
postsurgery. In addition to its direct action, praziquantel enhances the plasma
concentration of albendazole.
trials at a dosage of 25 mg/kg three times daily for 1–2 days indicate
effectiveness of praziquantel against fasciolopsia-sis, metagonimiasis, and
other forms of heterophyiasis. Praziquantel was not effective for fascioliasis,
however, even at dosages as high as 25 mg/kg three times daily for 3–7 days.
Mild and transient
adverse effects are common. They begin within several hours after ingestion of
praziquantel and may persist for about 1 day. Most common are headache,
dizziness, drowsiness, and lassitude; others include nausea, vomiting,
abdominal pain, loose stools, pruritus, urticaria, arthralgia, myalgia, and
low-grade fever. Mild and transient elevations of liver enzymes have been
reported. Several days after starting praziquantel, low-grade fever, pruritus,
and skin rashes (macular and urticarial), sometimes asso-ciated with worsened
eosinophilia, may occur, probably due to the release of proteins from dying
worms rather than direct drug tox-icity. The intensity and frequency of adverse
effects increase with dosage such that they occur in up to 50% of patients who
receive 25 mg/kg three times in 1 day.
neurologic abnormalities may be exac-erbated by inflammatory reactions around
dying parasites. Common findings in patients who do not receive
corticoster-oids, usually presenting during or shortly after therapy, are
head-ache, meningismus, nausea, vomiting, mental changes, and seizures (often
accompanied by increased cerebrospinal fluid pleocytosis). More serious
findings, including arachnoiditis, hyperthermia, and intracranial hypertension,
may also occur. Corticosteroids are commonly used with praziquantel in the
treatment of neurocysticercosis to decrease the inflammatory reaction, but this
is controversial and complicated by knowledge that corticosteroids decrease the
plasma level of praziquantel up to 50%. Praziquantel is contraindicated in
ocular cysticercosis, because parasite destruction in the eye may cause
irreparable damage. Some workers also caution against use of the drug in spinal
neurocysticercosis.The safety of praziquantel in children younger than age 4
years is not established, but no specific problems in young children have been
documented. Indeed, the drug appears to be better tolerated in children than in
adults. Praziquantel increased abortion rates in rats and therefore should be
avoided in pregnancy if possible. Because the drug induces dizziness and
drowsiness, patients should not drive during therapy and should be warned
regarding activities requiring particular physical coordination or alertness.