7.6 Antiparasitic and Anthelminthic Drugs

Parasitic and helminthic infections pose significant health challenges worldwide. These invaders, ranging from tiny protozoa to larger worms, can wreak havoc on the human body, causing a variety of symptoms and complications.

Understanding the mechanisms of infection and available treatments is crucial for healthcare providers. From antiprotozoal drugs to anthelmintics, a range of medications can combat these parasites, but careful consideration of effectiveness and side effects is essential for optimal patient care.

Parasitic and Helminthic Infections

Mechanisms of parasitic infections

Top images from around the web for Mechanisms of parasitic infections

• 

  File:Life Cycle of the Malaria Parasite.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  13.8B: Antiprotozoan and Antihelminthic Drugs - Biology LibreTexts View original

  Is this image relevant?

• 

  Parasitism - Wikipedia View original

  Is this image relevant?

• 

  File:Life Cycle of the Malaria Parasite.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  13.8B: Antiprotozoan and Antihelminthic Drugs - Biology LibreTexts View original

  Is this image relevant?

1 of 3

Top images from around the web for Mechanisms of parasitic infections

• 

  File:Life Cycle of the Malaria Parasite.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  13.8B: Antiprotozoan and Antihelminthic Drugs - Biology LibreTexts View original

  Is this image relevant?

• 

  Parasitism - Wikipedia View original

  Is this image relevant?

• 

  File:Life Cycle of the Malaria Parasite.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  13.8B: Antiprotozoan and Antihelminthic Drugs - Biology LibreTexts View original

  Is this image relevant?

1 of 3

• Parasitic protozoa or helminths invade and multiply within a host organism, deriving nutrients and causing harm to the host
• Protozoan parasites (Giardia, Cryptosporidium) typically infect the gastrointestinal tract, leading to diarrhea and malabsorption
• Helminthic parasites, including roundworms (Ascaris), tapeworms (Taenia), and flukes (Schistosoma), can infect various organs and tissues, resulting in a wide range of symptoms
• Parasites are transmitted through ingestion of contaminated food or water (Giardia), contact with infected feces (pinworms), penetration of skin by larvae (hookworms), or via insect vectors (malaria)
• Some parasites can be transmitted between animals and humans (zoonotic transmission)

Symptoms and diagnosis of infections

• Gastrointestinal symptoms manifest as diarrhea, abdominal pain, cramping, nausea, vomiting, weight loss, and malnutrition
• Systemic symptoms include fever, chills, fatigue, weakness, anemia, and nutrient deficiencies
• Microscopic examination of stool, blood, or tissue samples aids in identifying parasites or their eggs
• Serological tests detect antibodies or antigens specific to the parasite
• Imaging techniques (X-rays, CT scans) help visualize internal damage caused by parasitic infections

Antiparasitic and Anthelminthic Drugs

Major antiparasitic drugs

• Antiprotozoal drugs target specific protozoan parasites
  • Metronidazole disrupts DNA synthesis, causing cell death in anaerobic protozoa (Giardia, Entamoeba)
  • Chloroquine interferes with heme detoxification in malaria parasites (Plasmodium)
  • Nitazoxanide inhibits the pyruvate ferredoxin oxidoreductase enzyme, disrupting energy metabolism in protozoa (Cryptosporidium)
• Anthelmintic drugs combat parasitic worms
  • Benzimidazoles (albendazole, mebendazole) inhibit microtubule formation, impairing glucose uptake and causing paralysis in helminths
  • Pyrantel pamoate acts as a neuromuscular blocking agent, leading to paralysis in roundworms
  • Praziquantel increases cell membrane permeability, causing calcium influx and paralysis in tapeworms and flukes

Effectiveness vs side effects

• Drug effectiveness varies based on the specific parasite, chosen medication, dosage, treatment duration, and potential drug resistance
• Common side effects include gastrointestinal disturbances (nausea, vomiting, diarrhea), headache, dizziness, and fatigue
• Rarely, severe reactions such as liver toxicity or blood disorders may occur
• Antacids and iron supplements may reduce the absorption of some antiparasitic drugs
• Anticonvulsants and rifampin can decrease the effectiveness of certain anthelmintics
• Caution is needed when combining antiparasitic or anthelminthic drugs with medications that have similar side effects

Pharmacology of antiparasitic drugs

• Pharmacokinetics: The study of how the body processes antiparasitic drugs, including absorption, distribution, metabolism, and excretion
• Pharmacodynamics: The examination of how antiparasitic drugs interact with their targets and produce therapeutic effects
• Understanding these processes helps optimize dosing regimens and predict potential drug interactions

Nursing considerations for administration

• Assess for contraindications and allergies before administering medications
• Administer drugs with food or milk to minimize gastrointestinal side effects
• Monitor patients closely for adverse reactions and promptly report severe symptoms
• Ensure proper hydration and electrolyte balance, especially in patients experiencing diarrhea
• Educate patients on the importance of completing the full course of treatment
• Implement infection control measures to prevent the spread of parasitic or helminthic infections

Patient education for medications

• Explain the purpose and expected outcomes of the prescribed medication to the patient
• Provide clear instructions on dosage, administration, and duration of treatment
• Discuss potential side effects and when to seek medical attention
• Emphasize the importance of personal hygiene and sanitation to prevent reinfection
  • Encourage frequent handwashing, proper food cooking, and drinking clean water
  • Advise patients to avoid swimming in contaminated water sources and to wear protective clothing when necessary

Global impact of infections

• Parasitic and helminthic infections are highly prevalent in developing countries with poor sanitation and limited access to clean water
• These infections contribute to malnutrition, anemia, and impaired cognitive development, especially in children
• The burden of disease strains healthcare systems, requiring ongoing treatment and prevention efforts
• Challenges include developing effective vaccines, managing drug resistance, and improving diagnostic tools in resource-limited settings
• Public health interventions, such as mass drug administration and health education campaigns, are crucial for controlling and eliminating these infections