C H A P T E R 1 3
Anthelmintic agents
185
Therapeutic actions and indications
Anthelmintic agents are indicated for the treatment of
infections by certain susceptible worms and are very
specific in the worms that they affect; they are not inter-
changeable for treating various worm infections. See
Table 13.2 for usual indications for each of these agents.
Anthelmintics interfere with metabolic processes in
particular worms, as described previously. Figure 13.2
shows sites of actions for these drugs.
Pharmacokinetics
Mebendazole is available in the form of a chewable
tablet, and a typical 3-day course can be repeated in
3 weeks if needed. Very little of the mebendazole is
absorbed systemically, so adverse effects are few. The
drug is not metabolised in the body, and most of it is
excreted unchanged in the faeces. A small amount may
be excreted in the urine.
Albendazole is poorly absorbed from the gastroin-
testinal (GI) tract, reaching peak plasma levels in about
5 hours. It is metabolised in the liver and primarily
excreted in urine.
Ivermectin is readily absorbed from the GI tract and
reaches peak plasma levels in 4 hours. It is completely
metabolised in the liver with a half-life of 16 hours;
excretion is through the faeces.
experience. Swallow the tablets whole and avoid holding
them in your mouth for any length of time because a very
unpleasant taste may occur.
• Common effects of this drug include
•
Nausea, vomiting and loss of appetite:
Take the drug with
food, and eat small, frequent meals.
•
Dizziness and drowsiness:
If this occurs, avoid driving a car
or operating dangerous machinery. Change positions
slowly to avoid falling or injury.
• Report any of the following conditions to your healthcare
provider: fever, chills, rash, headache, weakness or tremors.
• Take all of the drug that has been prescribed. Never use
this drug to self-treat any other infection or give it to any
other person.
• Tell any doctor, nurse or other healthcare provider that
you are taking this drug.
• Keep this drug and all medications out of the reach of
children.
Rough
endoplasmic
reticulum
Smooth
endoplasmic reticulum
Polyribosomes
Golgi
apparatus
Cilia with
microtubules
Peroxisomes
Lysosomes
Nucleus:
Nuclear
membrane
Nuclear pore
Nucleolus
Cell membrane
Microtubules
Mitochondria
Centrioles
Praziquantel increases
membrane permeability,
causing cell death
Ivermectin blocks
calcium channels,
leading to nerve and
muscle paralysis
and cell death
Albendazole
blocks tubule
formation
Mebendazole
prevents cell
use of glucose
Pyrantel causes
paralysis and
cell death
FIGURE 13.2
General structure of a
cell, showing the sites of action of the
anthelmintic agents. Mebendazole
interferes with the ability to use
glucose, leading to an inability to
reproduce and cell death. Albendazole
blocks tubule formation, resulting in
cell death. Ivermectin blocks calcium
channels, leading to nerve and muscle
paralysis and cell death. Pyrantel is
a neuromuscular polarising agent
that causes paralysis and cell death.
Praziquantel increases membrane
permeability, leading to a loss of
intracellular calcium and muscular
paralysis; it may also result in
disintegration of the integument
