1. Antimalarial, Antiprotozoal, and Anthelmintic Drugs
Chapter 43
Antimalarial, Antiprotozoal, and Anthelmintic Drugs
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Protozoal Infections
Parasitic protozoa: live in or on humans
Malaria
Leishmaniasis
Amebiasis
Giardiasis
Trichomoniasis
Trypanosomiasis
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Malaria
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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5. 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
Asexual cycle: two phases
Exoerythrocytic phase
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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8. 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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11. 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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12. 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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13. 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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14. Classroom Response Question
When pyrimethamine is used to treat malaria, a sulfonamide antibiotic is often also used. The purpose of the antibiotic is to:
treat the bacterial infections that often accompany malaria.
allow the antimalarial drug to be effective in the exoerythrocytic phase.
cause synergism, allowing for a stronger antimalarial effect.
allow for reduced adverse effects because smaller doses of each drug are used.
Correct answer: C
Rationale: The combination of some antimalarial drugs with specific antibiotics results in synergistic effects, thus making the drugs more effective against the malarial infection.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

15. 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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16. Classroom Response Question
Before administration of primaquine, it is most important for the nurse to assess the patient for a history of which condition?
Asthma
Diabetes mellitus
Hypertension
Rheumatoid arthritis
Correct answer: D
Rationale: Primaquine is contraindicated in patients with allergy or any disease states that may cause granulocytopenia (rheumatoid arthritis, systemic lupus erythematosus). Primaquine must be used with caution in patients with methemoglobinemia, porphyria, methemoglobin reductase deficiency, and glucose-6-phosphate dehydrogenase (G6PD) deficiency.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

17. 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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18. 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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19. 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
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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22. 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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23. 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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24. 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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25. 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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26. 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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27. 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?
He will be given the inhaled form of pentamidine and be monitored closely.
He will be given the pentamidine in an IM or IV injection and be monitored closely.
Another drug, such as metronidazole (Flagyl), will be ordered.
He will receive supportive care because he is unable to take the pentamidine.
Correct answer: B
Rationale: Hypersensitivity is more common when the drug is administered by inhalation. An allergic reaction to the inhalational form does not preclude its administration by either the intramuscular or intravenous route, due to the seriousness of the Pneumocystis infection.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

28. 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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29. Classroom Response Question
A patient is taking metronidazole for amebiasis.
What information should the nurse include in the patient teaching?
How to check stool samples correctly and safely
Metronidazole may precipitate hypertension
Blurred vision is an expected effect of this medication, which will resolve with time
To take the medication on an empty stomach
Correct answer: A
Rationale: When the patient is taking metronidazole for amebiasis, the nurse should include in the instructions how to check stool samples correctly and safely, and how to dispose of samples properly. Metronidazole may precipitate dizziness, so encourage the patient to be cautious in all activities until a response to the drug is noted and is consistent. Encourage the patient to contact the prescriber if there is any visual disturbance noted. The medication should be taken with food to decrease gastrointestinal upset.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

30. 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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32. Anthelmintic Drugs (cont’d)
albendazole (Albenza)
ivermectin (Stromectol)
praziquantel (Biltricide)
pyrantel (Pin-X)
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33. 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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34. 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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35. 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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36. Anthelmintic Drugs: Adverse Effects
Effects will vary with each drug
Common adverse effects
Nausea
Vomiting
Diarrhea
Dizziness
Headache
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Nursing Implications
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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38. 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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39. 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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40. 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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41. 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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