In the treatment of S haematobium, an oral dose of 7.5–10 mg/kg is given three times at 14-day intervals. Cure rates on this schedule are 44–93%, with marked reductions in egg counts in those not cured. Metrifonate was also effective as a prophylactic agent when given monthly to children in a highly endemic area, and it has been used in mass treatment programs. In mixed infections with S haematobium and S mansoni, metrifonate has been successfully combined with oxamniquine.
Adverse Reactions, Contraindications, & Cautions
Some studies note mild and transient cholinergic symptoms, including nausea and vomiting, diarrhea, abdominal pain, bronchospasm, headache, sweating, fatigue, weakness, dizziness, and vertigo. Metrifonate should not be used after recent exposure to insecticides or drugs that might potentiate cholinesterase inhibition. It is contraindicated in pregnancy.
Niclosamide is a second-line drug for the treatment of most tapeworm infections, but it is not available in the USA.
Niclosamide is a salicylamide derivative. It appears to be minimally absorbed from the gastrointestinal tract—neither the drug nor its metabolites have been recovered from the blood or urine. Adult worms (but not ova) are rapidly killed, presumably due to inhibition of oxidative phosphorylation or stimulation of ATPase activity.
The adult dose of niclosamide is 2 g once, given in the morning on an empty stomach. The tablets must be chewed thoroughly and then swallowed with water.
1.
Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Diphyllobothrium latum (fish tapeworm)—A single 2-g dose of niclosamide results in cure rates of over 85% for D latum and about 95% for T saginata. It is probably equally effective against T solium. Cysticercosis can theoretically occur after treatment of T solium infections, because viable ova are released into the gut lumen after digestion of segments, but no such cases have been reported.
2.
Other tapeworms—Most patients treated with niclosamide for Hymenolepis diminuta and Dipylidium caninum infections are cured with a 7-day course of treatment; a few require a second course. Praziquantel is superior for Hymenolepis nana (dwarf tapeworm) infection. Niclosamide is not effective against cysticercosis or hydatid disease.
3.
Intestinal fluke infections—Niclosamide can be used as an alternative drug in the treatment of Fasciolopsis buski, Heterophyes heterophyes, and Metagonimus yokogawai infections. The standard dose is given every other day for three doses.
Adverse Reactions, Contraindications, & Cautions
Infrequent, mild, and transitory adverse events include nausea, vomiting, diarrhea, and abdominal discomfort. Alcohol should not be consumed during or for 1 day after treatment. Safety has not been established in pregnancy or for children younger than 2 years.
Oxamniquine is an alternative to praziquantel for the treatment of S mansoni infections. It has also been used extensively for mass treatment. It is not effective against S haematobium or S japonicum. It is not available in the USA.
Oxamniquine, a semisynthetic tetrahydroquinoline, is readily absorbed orally; it should be taken with food. Its plasma half-life is about 2.5 hours. The drug is extensively metabolized to inactive metabolites and excreted in the urine—up to 75% in the first 24 hours. Intersubject variations in serum concentration have been noted, which may explain some treatment failures.