Chapter 43
Antimalarial, Antiprotozoal,
and Anthelmintic Drugs
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Protozoal Infections

Parasitic protozoa: live in or on humans

Malaria
 Leishmaniasis
 Amebiasis
 Giardiasis
 Trichomoniasis
 Trypanosomiasis
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Malaria



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Caused by Plasmodium protozoa
Four different Plasmodium species
Transmitted by the bite of an infected adult
female anopheline mosquito
Can also be transmitted by infected individuals
via blood transfusion, congenitally, or from
infected needles by drug abusers
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Malarial Parasite (Plasmodium)



Two interdependent life cycles
Sexual cycle: occurs in the mosquito
Asexual cycle: occurs in the human


Knowledge of the life cycles is essential in
understanding antimalarial drug treatment
Drugs are effective only during the asexual cycle
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Plasmodium Life Cycle
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
Asexual cycle: two phases
Exoerythrocytic phase
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
Occurs “outside” the erythrocyte
Also known as the tissue phase
Erythrocytic phase


Occurs “inside” the erythrocyte
Also known as the blood phase
Erythrocytes = RBCs
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Classic Malaria Paroxysm



Chills and rigors, followed by fever of up to 104°
F (40° C) and diaphoresis, frequently leading to
extreme fatigue and prolonged sleep
This syndrome often repeats itself periodically in
48- to 72-hour cycles
Other common symptoms include headache,
nausea, and joint pain
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Treatment of Malaria


Not initiated until the diagnosis has been
confirmed with diagnostic tests
Treatment is guided by:

The infecting Plasmodium species
 Clinical status of the patient
 Drug susceptibility of the infecting parasites as
determined by the geographic area where the
infection was acquired
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Antimalarial Drugs

Attack the parasite during the asexual phase,
when it is vulnerable



Erythrocytic phase drugs: chloroquine,
hydroxychloroquine, quinine, mefloquine,
pyrimethamine
Primaquine: kills parasite in both phases
May be used together or with a sulfonamide for
synergistic or additive killing power
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Antimalarial Drugs:
Mechanism of Action

4-Aminoquinoline derivatives: chloroquine and
hydroxychloroquine

Bind to parasite nucleoproteins and interfere with
protein synthesis; also alter pH within the parasite
 Interfere with parasite’s ability to metabolize and use
erythrocyte hemoglobin
 Effective only during the erythrocytic phase
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Antimalarial Drugs:
Mechanism of Action (cont’d)

Quinine and mefloquine

Alter pH within the parasite
 Interfere with parasite’s ability to metabolize and use
erythrocyte hemoglobin
 Effective only during the erythrocytic phase
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Antimalarial Drugs:
Mechanism of Action (cont’d)

Diaminopyrimidines (pyrimethamine and
trimethoprim)

Inhibit protein synthesis essential for growth and
survival
 Only effective during the erythrocytic phase
 May be used with sulfadoxine or dapsone for
synergistic effects
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Classroom Response Question
When pyrimethamine is used to treat malaria, a
sulfonamide antibiotic is often also used. The purpose of
the antibiotic is to:
A. treat the bacterial infections that often accompany
malaria.
B. allow the antimalarial drug to be effective in the
exoerythrocytic phase.
C. cause synergism, allowing for a stronger antimalarial
effect.
D. allow for reduced adverse effects because smaller
doses of each drug are used.
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Antimalarial Drugs:
Mechanism of Action (cont’d)

Primaquine



Only exoerythrocytic drug (works in both phases)
Binds and alters parasitic DNA
Sulfonamides, tetracyclines, clindamycin

Used in combination with antimalarials for synergistic
effects
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Classroom Response Question
Before administration of primaquine, it is most
important for the nurse to assess the patient for a
history of which condition?
A. Asthma
B. Diabetes mellitus
C. Hypertension
D. Rheumatoid arthritis
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Antimalarial Drugs: Drug Effects


Kill parasitic organisms
Hydroxychloroquine



Has antiinflammatory effects
Sometimes used in the treatment of rheumatoid
arthritis and systemic lupus erythematosus
Quinine and quinidine


Decrease the excitability of both cardiac and skeletal
muscles
Quinidine is still currently used to treat certain types
of cardiac dysrhythmias
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Antimalarial Drugs: Indications



Used to kill Plasmodium organisms, the
parasites that cause malaria
The drugs have varying effectiveness on
the different malaria organisms
Some drugs are used for prophylaxis against
malaria
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Antimalarial Drugs: Adverse Effects


Many adverse effects for the various drugs
Primarily gastrointestinal

Nausea
 Vomiting
 Diarrhea
 Anorexia
 Abdominal pain
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Antiprotozoal Drugs

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
atovaquone (Mepron)
metronidazole (Flagyl)
pentamidine (Pentam 300)
paromomycin (Humatin)
Several drugs used to treat malaria are also
used to treat nonmalarial protozoal infections
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Protozoal Infections





Amebiasis
Giardiasis
Pneumocystosis
Toxoplasmosis
Trichomoniasis
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Protozoal Infections (cont’d)

Transmission

Person to person
 Ingestion of contaminated water or food
 Direct contact with the parasite
 Insect bite (mosquito or tick)
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Protozoal Infections (cont’d)

Patients with compromised immune systems are
at risk for acquiring these infections

Patients taking immunosuppressive drugs after a
transplant
 Patients with leukemia
 AIDS patients

Protozoal infections are often fatal in these
cases
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Antiprotozoal Drugs: Mechanism of
Action and Indications

atovaquone (Mepron)

Protozoal energy comes from the mitochondria
 Atovaquone: selective inhibition of mitochondrial
electron transport
 Result: no energy, leading to cellular death
• Used to treat mild to moderate Pneumocystis jirovecii
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Antiprotozoal Drugs: Mechanism of
Action and Indications (cont’d)

metronidazole (Flagyl)

Disruption of DNA synthesis as well as nucleic acid
synthesis
 Bactericidal, amebicidal, trichomonacidal
 Used for treatment of trichomoniasis, amebiasis,
giardiasis, and antibiotic-associated
pseudomembranous colitis
 Tinidazole (Tindamax) is a newer, similar drug.
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Antiprotozoal Drugs: Mechanism of
Action and Indications (cont’d)

pentamidine (NebuPent, Pentam 300)



Inhibits protein and nucleic acid synthesis
Used mainly for the treatment of active P. jirovecii
pneumonia and for prophylaxis of P. jirovecii
pneumonia in patients at high risk for initial or
recurrent Pneumocystis infection, such as patients
with HIV infection and AIDS
Sometimes used to treat various other protozoal
infections
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Classroom Response Question
A male patient with an HIV infection has a severe case of P. jirovecii
pneumonia (PJP) and needs to be treated with pentamidine. However,
he is allergic to the inhaled form of this medication. Considering the
seriousness of his condition, what does the nurse expect will be done in
this situation?
A. He will be given the inhaled form of pentamidine and be monitored
closely.
B. He will be given the pentamidine in an IM or IV injection and be
monitored closely.
C. Another drug, such as metronidazole (Flagyl), will be ordered.
D. He will receive supportive care because he is unable to take the
pentamidine.
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Antiprotozoal Drugs:
Adverse Effects

atovaquone (Mepron)


Nausea, anorexia, constipation, increased liver
enzyme levels, many others
metronidazole (Flagyl)

Metallic taste, vomiting, diarrhea, headache, many
others
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Classroom Response Question
A patient is taking metronidazole for amebiasis.
What information should the nurse include in the
patient teaching?
A. How to check stool samples correctly and safely
B. Metronidazole may precipitate hypertension
C. Blurred vision is an expected effect of this
medication, which will resolve with time
D. To take the medication on an empty stomach
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Antiprotozoal Drugs:
Adverse Effects (cont’d)

pentamidine

Bronchospasms
 Leukopenia
 Thrombocytopenia
 Acute pancreatitis
 Nephrotoxicity
 Increased liver enzyme levels
 Hypotension
 Many others
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Anthelmintic Drugs



Drugs used to treat parasitic worm infections:
helminthic infections
Unlike protozoa, helminths are large and have
complex cellular structures
Drug treatment is very specific to the organism
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Anthelmintic Drugs (cont’d)
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


albendazole (Albenza)
ivermectin (Stromectol)
praziquantel (Biltricide)
pyrantel (Pin-X)
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Anthelmintic Drugs (cont’d)


It is very important to identify the causative worm
Done by finding the parasite ova or larvae in
feces, urine, blood, sputum, or tissue

Cestodes (tapeworms)
 Nematodes (roundworms)
 Trematodes (flukes)
 Platyhelminthes (flatworms)
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Anthelmintic Drugs: Mechanism of
Action and Indications

praziquantel (Biltricide)



Paralyzes worms’ musculature and immobilizes their
suckers
Causes worms to dislodge from mesenteric veins to
the liver; then killed by host tissue reactions
Used to treat fluke infections, some tapeworms
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Anthelmintic Drugs: Mechanism of
Action and Indications (cont’d)

pyrantel (Pin-X)



Pyrimidine-derived anthelmintic drug that is indicated
for the treatment of infection with intestinal
roundworms, including ascariasis, enterobiasis, and
other helminthic infections
Only anthelmintic available in the United States
without a prescription
Available only for oral use
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Anthelmintic Drugs:
Adverse Effects


Effects will vary with each drug
Common adverse effects

Nausea
 Vomiting
 Diarrhea
 Dizziness
 Headache
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Nursing Implications
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


Before beginning therapy, perform a thorough
health history and medication history, and
assess for allergies
Be sure to collect specimens before beginning
drug therapy
Check baseline vital signs
Check for conditions that may contraindicate
use, and for potential drug interactions
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Nursing Implications (cont’d)



Some drugs may cause the urine to have an
asparagus-like odor, or cause an unusual skin
odor or a metallic taste; be sure to warn the
patient ahead of time
Administer all drugs as ordered and for the
prescribed length of time
Most drugs should be taken with food to reduce
GI upset
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Antimalarial Drugs:
Nursing Implications



Assess for presence of malarial symptoms
When used for prophylaxis, these drugs should
be started 1 to 2 weeks before potential
exposure to malaria, and for 4 to 8 weeks after
leaving the area
Medications are taken weekly, with 8 ounces of
water
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Antimalarial Drugs:
Nursing Implications (cont’d)


Instruct patient to notify prescriber immediately if
ringing in the ears, hearing decrease, visual
difficulties, nausea, vomiting, profuse diarrhea,
or abdominal pain occurs
Alert patient to the possible recurrence of the
symptoms of malaria so that he or she will know
to seek immediate treatment
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Nursing Implications (cont’d)

Monitor for adverse effects


Ensure that patients know the adverse effects that
should be reported
Monitor for therapeutic effects and adverse effects
with long-term therapy
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