Chapter 43 Antimalarial, Antiprotozoal, and Anthelmintic Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc

Chapter 43

Antimalarial, Antiprotozoal, and Anthelmintic Drugs

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Parasitic protozoa: live in or on humans Malaria Leishmaniasis Amebiasis Giardiasis Trichomoniasis Trypanosomiasis

Protozoal Infections

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 2

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

Malaria



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

Malarial Parasite (Plasmodium)


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

Plasmodium Life Cycle



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

Classic Malaria Paroxysm


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

Treatment of Malaria


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

Antimalarial Drugs


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

Antimalarial Drugs: Mechanism of Action


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

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



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.


Primaquine Only exoerythrocytic drug (works in both phases) Binds and alters parasitic DNA

Sulfonamides, tetracyclines, clindamycin Used in combination with antimalarials for synergistic

effects




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


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

Antimalarial Drugs: Drug Effects


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

Antimalarial Drugs: Indications


Many adverse effects for the various drugs Primarily gastrointestinal

Nausea Vomiting Diarrhea Anorexia Abdominal pain

Antimalarial Drugs: Adverse Effects


atovaquone (Mepron) metronidazole (Flagyl) pentamidine (Pentam 300) paromomycin (Humatin) Several drugs used to treat malaria are also

used to treat nonmalarial protozoal infections

Antiprotozoal Drugs


Amebiasis Giardiasis Pneumocystosis Toxoplasmosis Trichomoniasis

Protozoal Infections


Transmission Person to person Ingestion of contaminated water or food Direct contact with the parasite Insect bite (mosquito or tick)

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

Protozoal Infections (cont’d)


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

Antiprotozoal Drugs: Mechanism of Action and Indications


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.

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

Antiprotozoal Drugs: Mechanism of Action and Indications (cont’d)


Classroom Response QuestionA 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.


atovaquone (Mepron) Nausea, anorexia, constipation, increased liver

enzyme levels, many others metronidazole (Flagyl)

Metallic taste, vomiting, diarrhea, headache, many others

Antiprotozoal Drugs: Adverse Effects



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


pentamidine Bronchospasms Leukopenia Thrombocytopenia Acute pancreatitis Nephrotoxicity Increased liver enzyme levels Hypotension Many others

Antiprotozoal Drugs: Adverse Effects (cont’d)


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

Anthelmintic Drugs


albendazole (Albenza) ivermectin (Stromectol) praziquantel (Biltricide) pyrantel (Pin-X)

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)

Anthelmintic Drugs (cont’d)


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

Anthelmintic Drugs: Mechanism of Action and Indications


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

Anthelmintic Drugs: Mechanism of Action and Indications (cont’d)


Effects will vary with each drug Common adverse effects

Nausea Vomiting Diarrhea Dizziness Headache

Anthelmintic Drugs: Adverse Effects


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

Nursing Implications


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

Nursing Implications (cont’d)


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

Antimalarial Drugs: Nursing Implications


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

Antimalarial Drugs: 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

Nursing Implications (cont’d)


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Chapter 43 Antimalarial, Antiprotozoal, and Anthelmintic Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc