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Pharmacology · chapter 7 · Anti-infective Drugs

Antiparasitic and Anthelminthic Drugs

The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.

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Key points

  1. How protozoal infections spread

    Many of these conditions affect clients living in areas with poor sanitation because the spread can be attributed to either fecal-contaminated water or fecal–oral transfer.

  2. Signs of protozoal infection

    Signs and symptoms of protozoal infections include diarrhea, low-grade fever, nausea, greasy stools, and depressed appetite.

  3. Diagnosis from stool samples

    Intestinal protozoal infections are most often diagnosed from microscopic stool samples, although molecular tests have recently been developed that may allow faster detection of infections.

  4. The organism decides the drug

    It is important to ensure that an accurate diagnosis has been made regarding the causative organism because this will dictate which medication is most appropriate for the client.

  5. Tinidazole and alcohol

    Tinidazole is contraindicated in clients consuming alcohol while using the drug due to risk for causing a severe flushing reaction.

  6. Why lice come back

    Lice can be difficult to treat because if the eggs (nits) are not successfully removed from the hair after treatment, reinfestation can occur.

  7. Nits survive pediculicides

    Clinical Tip Ensure Removal of Nits Nits are the eggs of lice that attach to the hair, and they are unaffected by pediculicides.

  8. Comb the hair after treatment

    To ensure that nits do not go on to mature into adults requiring further pediculicide treatment, it is important to carefully comb through the hair with a fine-tooth nit comb after using a pediculicide.

  9. Ivermectin: topical and oral uses

    When used topically, it can treat lice and scabies infestations; when taken orally, it can treat a variety of helminth infections.

  10. Common adverse effects

    Most oral antiprotozoal and anthelminthic drugs can cause gastrointestinal upset. Any topical scabicides and pediculicides may cause skin irritation to the area where they are applied.

  11. Lindane and seizures

    Excessive use of lindane is not recommended in high doses, especially in children, because it can cause central nervous system excitation and seizure.

  12. Malathion and children

    Malathion should be kept away from children because ingesting it could cause cholinergic poisoning.

  13. Finish the whole course

    Advise the client to take the entire prescribed course of the medication to ensure adequate treatment and to reduce the development of drug resistance.

  14. Metronidazole and alcohol

    Avoid taking tinidazole or metronidazole with alcohol because the interaction can cause a severe flushing reaction.

Terms to know

Protozoa
Protozoa: Protozoa are unicellular organisms that replicate within a human host.
Helminths
Helminths: Helminths, or worms, are large complex organisms that can be consumed while they are in a larval stage and then mature into their adult stage in the host’s gastrointestinal tract.

Practice questions

Stuck on select-all-that-apply? How to take them one option at a time.

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Every question here, with the answer

  1. A client is prescribed metronidazole for giardiasis. Which statement by the client shows a need for more teaching?

    1. If I miss a dose, I will not take a double dose.
    2. I will take the pills with food if they upset my stomach.
    3. I will take the whole course even if I feel better.
    4. I can have a beer with dinner while I am on this drug.

    Answer: I can have a beer with dinner while I am on this drug.

    Metronidazole and tinidazole must not be taken with alcohol because the interaction can cause a severe flushing reaction. Taking the drug with food for stomach upset, finishing the course and not doubling doses are all correct teaching.

  2. A parent has treated a child's head lice with a pediculicide. What should the nurse teach the parent to do next?

    1. Carefully comb through the hair with a fine-tooth nit comb.
    2. Repeat the pediculicide every day for two weeks.
    3. Give the child an oral anthelminthic.
    4. Nothing more; the pediculicide also kills the eggs.

    Answer: Carefully comb through the hair with a fine-tooth nit comb.

    Nits are unaffected by pediculicides, so the hair must be combed with a fine-tooth nit comb or the eggs can mature and cause reinfestation. Repeating the product daily does not remove nits, and oral anthelminthics treat worms, not lice.

  3. A nurse is caring for a child with scabies. Which order should the nurse question?

    1. Repeated high-dose applications of lindane
    2. Teaching the family to report signs of an allergic reaction
    3. Monitoring the skin for irritation at the application site
    4. Topical permethrin

    Answer: Repeated high-dose applications of lindane

    Excessive or high-dose lindane is not recommended, especially in children, because it can cause central nervous system excitation and seizures; its black box warning reports seizures and deaths after repeated or prolonged use. The other actions are appropriate.

  4. A client has an intestinal protozoal infection. Which signs and symptoms should the nurse expect? Select all that apply.

    1. Depressed appetite
    2. Greasy stools
    3. Low-grade fever
    4. Diarrhea
    5. Seizures

    Answer: Depressed appetite, Greasy stools, Low-grade fever, Diarrhea

    The section lists diarrhea, low-grade fever, nausea, greasy stools and depressed appetite as signs of protozoal infection. Seizures are not listed; in this section they are linked to excessive lindane use.

  5. A nurse is teaching a client who is going home on an oral antiparasitic drug. Which instructions should the nurse include? Select all that apply.

    1. Take the entire prescribed course.
    2. Report throat swelling, severe itching, rash or chest tightness.
    3. Stop the drug once the diarrhea stops.
    4. Take a double dose if you miss one.
    5. Keep well hydrated.

    Answer: Take the entire prescribed course., Report throat swelling, severe itching, rash or chest tightness., Keep well hydrated.

    Clients should finish the full course to ensure treatment and reduce drug resistance, maintain adequate hydration, and report signs of an allergic reaction. Stopping early works against finishing the course, and double doses should not be taken.

  6. A family uses malathion for head lice. Which safety instruction is most important?

    1. Store it where children cannot reach it, because swallowing it can cause poisoning.
    2. Take it by mouth if the scalp becomes irritated.
    3. Apply it to the child's scalp with a nit comb daily for a month.
    4. Mix it with shampoo to make it less harmful.

    Answer: Store it where children cannot reach it, because swallowing it can cause poisoning.

    Malathion is an organophosphate and should be kept away from children because ingesting it could cause cholinergic poisoning. Daily prolonged use, oral use and mixing with shampoo are not supported by the section.

Where every quote comes from

Section 7.6 Antiparasitic and Anthelminthic Drugs of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.

The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.