Anthelmintic Agents 363in liver and excreted in urine. It can be
safely used in pregnancy.
Adverse effects include nausea,
vomiting, epigastric distress, skin rash,
urticaria, headache and seizures.
PYRANTEL PAMOATE
It is a broad spectrum anthelmintic effective
in pinworm, ascariasis and hook worm
infestation. It exerts its action by producing
persistent nicotinic receptor activation which
results in spastic paralysis of worms.
It is poorly absorbed from GIT and is
active against luminal organisms. It is
excreted in urine as metabolites and in
unchanged form. Adverse reactions
include rash, nausea, vomiting, headache,
dizziness, anorexia and elevation of SGOT
levels.
DIETHYLCARBAMAZINE
It is the drug of choice for filariasis. It is
effective against W. malayi, W. bancrofti, Loa
loa and Onchocerca volvulus.
It has a dual action. Hyperpolarization
effect of piperazine moiety causes
paralysis of the worms and alteration in
microfilarial surface membrane makes
them susceptible to destruction by host
defence mechanism.
It is absorbed after oral administration,
distributed all over body, metabolized in
liver and excreted in urine.
Adverse effects include anorexia,
nausea, vomiting, skin rash, urticaria,
fatigue, dizziness and headache.
It is indicated in filariasis and
tropical eosinophilia.
IVERMECTIN
Semisynthetic derivative of drug
obtained from Streptomyces avermitilis.
Ivermectin binds selectively and with
high affinity to glutamate gated chloride
ion channels in invertebrate nerve and
muscle cells. This leads to an increase in
the permeability of cell membrane to
chloride ions with hyperpolarization of
nerve of muscle cell, resulting in paralysis
and death of the parasite.
Following the oral administration of
ivermectin, peak plasma concentration is
achieved in four hours. Ivermectin is
absorbed well on an empty stomach. The
bioavailability is 50 to 60%. It is mainly
metabolized in the liver and the tissue
concentration is maximum in liver and fat.
Ivermectin and its metabolites are excreted
mainly in faeces.
Adverse effects include nausea,
vomiting, abdominal pain, constipation and
fatigue.
It is mainly indicated in scabies,
ascariasis trichuriasis, strongyloidiasis,
enterobiasis, filariasis, onchocerciasis (River
blindness) and elephantiasis. It is drug of
choice for onchocerciasis producing long
lasting reduction in microfilaria without
affecting adult worm.PRAZIQUANTEL
Effective against schistosomes, other
trematodes, cestodes and their larval forms
but not against nematodes.
It causes spastic paralysis of worms
due to leakage of intracellular calcium
from membranes. At high concentration
it causes vacuolization of tegument and
release of contents of worms and their
destruction by host defence mechanism.