Anthelmintic Agents

Two Types of Helminths Commonly Infecting Humans

• Nematodes or roundworms
  • Pinworms, whipworms, threadworms, Ascaris, and hookworms
• Platyhelminthes or flatworms
  • Cestodes (tapeworms) and flukes (schistosomes)

Measures to Control Infection

• Keep nails short
• Keep hands clean
• Frequent handwashing
• Shower in the morning
• Change and launder undergarments, bed linens, and pajamas daily
• Disinfect toilet seat daily
• Handwashing after using the bathroom

Tissue-Invading Worms

• Trichinosis
  • Caused by ingestion of the encysted larvae of the roundworm, Trichinella spiralis, in undercooked pork
• Filariasis
  • Infection of the blood and tissues of healthy individuals by worm embryos, injected by insects
• Schistosomiasis
  • Infection by a fluke that is carried by a snail

Life Cycle of Schistosoma

 

Mebendazole (Vermox)

• Most commonly used of all of the anthelmintics
• Effective against pinworms, roundworms, whipworms, and hookworms
• Available in the form of a chewable tablet
• Few adverse effects
• Not metabolized in the body; most is excreted unchanged in the feces
• Should not be used during pregnancy

Pyrantel (Antiminth, Pin-Rid, Pin-X, Reese’s Pinworm)

• Oral drug effective against pinworms and roundworms
• Given as a single dose
• Poorly absorbed; excreted unchanged in the feces
• Not recommended for use during pregnancy and lactation
• Safety not established for children age <2 years
• Adverse effects may include GI side effects and diarrhea

Thiabendazole (Mintezol)

• Treats roundworm, hookworm, and whipworm infections
• Not the anthelmintic drug of choice (not as effective, more adverse effects)
• Best drug for treatment of threadworm infections
• Readily absorbed from the GI tract; reaches peak levels in 1 to 2 hours
• Metabolized in the liver and excreted in the urine

Albendazole (Albenza)

• Treats active lesions caused by pork tapeworm and cystic disease of the liver, lungs, and peritoneum caused by dog tapeworm
• Serious adverse effects
• Should be used only after causative worm is identified
• Poorly absorbed from the GI tract; reaches peak levels in about 5 hours
• Metabolized in the liver and primarily excreted in the urine
• Should not be used during pregnancy and lactation

Ivermectin (Stromectol)

• Effective against the nematode that causes onchocerciasis, or river blindness
• Used to treat threadworm disease or strongyloidiasis
• Readily absorbed from the GI tract; reaches peak plasma levels in 4 hours
• Completely metabolized in the liver with a half-life of 16 hours; excreted through the feces
• Should never be taken during pregnancy; used with caution during lactation

Praziquantel (Biltricide)

• Very effective in the treatment of a wide number of schistosomes, or flukes
• Taken in a series of three doses at 4- to 6-hour intervals
• Has relatively few adverse effects
• Rapidly absorbed from the GI tract; reaches peak plasma levels within 1 to 3 hours
• Metabolized in the liver with a half-life of 0.8 to 1.5 hours
• Excreted primarily through the urine

Anthelmintic Actions/Indications

• Affects metabolic processes that are different in worms than in human hosts or are not found in humans
• Causes death of the worm by interfering with normal functioning

Anthelmintic Contraindications

• Presence of known allergy to any of these drugs
• Lactation
• Pregnancy (in most cases)
• Caution should be used in the presence of renal or hepatic disease or severe diarrhea and malnourishment

Anthelmintic Adverse Effects

• Abdominal discomfort
• Diarrhea
• Pain
• Headache
• Dizziness
• Fever
• Chills

Anthelmintic Drug-to-Drug Interactions

• Theophylline = increased levels of theophylline
• Albendazole with dexamethasone increases the overall effect of the drug

Sites of Action of the Anthelmintic Drugs

 

 

Use of Anthelmintic Agents Across the Lifespan

Prototype Anthelmintic Agent

Drug/Dosage/Indication

Nursing Considerations for Anthelmintic Agents

• Assessment (history and physical exam)
• Nursing diagnosis
• Implementation
• Evaluation