Lippincott Chapter 44: Anthelmintic Drugs

Question 1

CHEMOTHERAPY OF HELMINTIC
INFECTIONS: FOR NEMATODES

cestodes (tapeworms), trematodes (flukes) and nematodes (roundworms).

Answer 1

Diethylcarbamazine BANOCIDE
Ivermectin STROMECTOL
Mebendazole VERMOX
Pyrantel pamoate PIN-X
Thiabendazole MINTEZOL

Question 2

CHEMOTHERAPY OF HELMINTIC
INFECTIONS: FOR TREMATODES

Answer 2

Praziquantel BILTRICIDE

Question 3

CHEMOTHERAPY OF HELMINTIC
INFECTIONS: FOR CESTODES

Answer 3

Albendazole ALBENZA
Niclosamide

Question 4

Drug treatment for nematodes
Mebendazole

Answer 4

Mebendazole
Mebendazole [me-BEN-da-zole], a synthetic benzimidazole com-
pound, is a first-line agent for the treatment of infections caused by
whipworms (Trichuris trichiura), pinworms (Enterobius vermicularis),
hookworms (Necator americanus and Ancylostoma duodenale), and
roundworms (Ascaris lumbricoides). Mebendazole acts by inhibiting
the assembly of the microtubules in the parasite and also by irre-
versibly blocking glucose uptake. Affected parasites are expelled
in the feces. Adverse effects include abdominal pain and diarrhea.
Mebendazole should not be used in pregnant women. [Note: Many
anthelmintics should be avoided in pregnancy (Figure 44.3); however,
in mass prevention or treatment programs, certain agents (for exam-
ple, mebendazole or albendazole) may be used in the second or third
trimester.]

Question 5

Pyrantel pamoate

Answer 5

Pyrantel pamoate [pi-RAN-tel PAM-oh-ate] is also effective in the
treatment of infections caused by roundworms, pinworms, and hook-
worms (Figure 44.4). Pyrantel pamoate is poorly absorbed orally and
exerts its effects in the intestinal tract. It acts as a depolarizing, neuro-
muscular-blocking agent, causing release of acetylcholine and inhibi-
tion of cholinesterase, leading to paralysis of the worm. The paralyzed worm releases its hold on the intestinal tract and is expelled. Adverse
effects are mild and include nausea, vomiting, and diarrhea.

Question 6

Thiabendazole

Answer 6

Thiabendazole [thye-a-BEN-da-zole], a synthetic benzimidazole, is a
potent broad-spectrum anthelmintic agent. Current use of thiaben-
dazole is limited to the topical treatment of cutaneous larva migrans
(creeping eruption). Because of its toxic effects, it has been largely
replaced by other agents for many clinical applications.

Question 7

Ivermectin

Answer 7

Ivermectin [eye-ver-MEK-tin] is the drug of choice for the treatment of
cutaneous larva migrans, strongyloidiasis, and onchocerciasis (river
blindness) caused by Onchocerca volvulus (kills microfilariae but has
no activity against adult worms). [Note: Ivermectin is also useful in
the treatment of pediculosis (lice) and scabies.] Ivermectin targets
the glutamate-gated chloride channel receptors. Chloride influx is
enhanced, and hyperpolarization occurs, resulting in paralysis and
death of the worm. The drug is given orally and does not readily cross
the blood–brain barrier. Ivermectin should not be used in pregnancy
(Figure 44.3). The killing of the microfilaria in onchocerciasis can
result in a dangerous Mazzotti reaction (fever, headache, dizziness,
somnolence, and hypotension). The severity of this reaction is related
to parasite load. Antihistamines or steroids may be given to amelio-
rate the symptoms.

Question 8

Diethylcarbamazine

Answer 8

Diethylcarbamazine [dye-eth-il-kar-BAM-a-zeen] is the drug of choice
for filariasis caused by infection with Wuchereria bancrofti and Brugia
malayi. It kills the microfilariae and has activity against adult worms.
[Note: In countries where filariasis is endemic, a combination of anti-
filarial drugs (either diethylcarbamazine and albendazole or iver-
mectin and albendazole) may be used as preventive chemotherapy.]
Diethylcarbamazine is rapidly absorbed following oral administration
with meals and is excreted mainly in the urine. Adverse effects may
include fever, nausea, vomiting, arthralgia, and headache. [Note:
Diethylcarbamazine can accelerate blindness and cause severe
Mazzotti reactions in patients with onchocerciasis. It should be
avoided in patients with this disorder.]

Question 9

Drug treatment for nematodes

Praziquantel

Answer 9

Praziquantel
Praziquantel [pray-zi-KWON-tel] is an agent of choice for the
treatment of all forms of schistosomiasis, other trematode infec-
tions, and cestode infections such as taeniasis. Praziquantel is
also used off-label in the treatment of cysticercosis (caused by Taenia solium larvae; Figure 44.6). Permeability of the cell mem-
brane to calcium is increased, causing contracture and paralysis
of the parasite. Praziquantel should be taken with food and not
chewed due to a bitter taste. It is rapidly absorbed after oral
administration and distributes into the cerebrospinal fluid (CSF).
The drug is extensively metabolized, and the inactive metabo-
lites are excreted primarily in the urine. Common adverse effects
include dizziness, malaise, and headache as well as gastrointes-
tinal upset. Dexamethasone, phenytoin, rifampin, and carbam-
azepine may increase the metabolism of praziquantel. Cimetidine
causes increased praziquantel levels. Praziquantel is contraindi-
cated for the treatment of ocular cysticercosis, because destruc-
tion of the organism in the eye may cause irreversible damage.

Question 10

Drug treatment for CESTODES

Niclosamide

Answer 10

Niclosamide [ni-KLOE-sa-mide] (no longer available in the United
States) is an alternative to praziquantel for the treatment of taeniasis,
diphyllobothriasis, and other cestode infections. It inhibits the mito-
chondrial phosphorylation of adenosine diphosphate (ADP) in the
parasite, making it lethal for the cestode’s scolex and segments but
not for the ova. Anaerobic metabolism may also be inhibited. A laxa-
tive is administered prior to oral administration to purge the bowel of
all dead segments and to enhance digestion and liberation of the ova.
Alcohol should be avoided within 1 day of niclosamide use.

Question 11

Albendazole

Answer 11

Albendazole [al-BEN-da-zole], another benzimidazole, inhibits micro-
tubule synthesis and glucose uptake in nematodes and is effective against most nematodes known. Its primary therapeutic application,
however, is in the treatment of cestodal infestations, such as cysticer-
cosis and hydatid disease (caused by larval stage of Echinococcus
granulosus). [Note: Albendazole is also very effective in treat-
ing microsporidiosis, a fungal infection.] Albendazole is erratically
absorbed after oral administration, but absorption is enhanced by a
high-fat meal. The drug distributes widely, including the CSF. It under-
goes extensive first-pass metabolism, including formation of an active
sulfoxide. Albendazole and its metabolites are primarily excreted in
the bile. When used in short-course therapy (1 to 3 days) for nema-
todal infestations, adverse effects are mild and transient and include
headache and nausea. Treatment of hydatid disease (3 months) has
a risk of hepatotoxicity and, rarely, agranulocytosis or pancytopenia.
Medical treatment of neurocysticercosis is associated with inflamma-
tory responses to dying parasites in the CNS, including headache,
vomiting, fever, and seizures.