• Single-Celled Eukaryotes
• Can replicate intracellularly (Plasmodium spp.) OR extracellularly in intestines (Giardia lamblia), blood (Trypanosoma), urogenital (Trichomonas vaginalis)
• All protozoa surrounded by a unit membrane similar to cell membrane of all eukaryotes
• Some have a very thin plasmalemma whereas others have a rigid body wall (flagellates and ciliates) called a pellicle

Symptomatic Amoebiasis

• Abdominal discomfort
• Loss of appetite
• Metallic taste
• Disulfiram-Like Reaction - wait at least 3 days after cessation of therapy to drink alcohol

• Black Box Warning: May cause severe dermatologic reactions including Stevens-Johnson Syndrome
• Causes photosensitivity
• Take with plenty of water to prevent crystallization in the kidneys
• The drug is a folic acid synthesis inhibitor -- take with Folic Acid

• Multicellular eukaryotes
• Most alternate between sexual reproduction in definitive host and asexual in intermediate host or vector
• Adults don't multiply in hosts but do generate eggs or larvae -- they can do damage and it depends on infective load

Trichinella spiralis

Necator americanus

Enterobius vermicularis

Ascaris lumbricoides

• Outer protective cuticle (tegument)
• Outer portion of tegument has glycocalyx, a protective zone that inhibits the action of digestive enzymes
• Some have tegumental spines
• Layer of muscle below

Praziquantel

• Mebendazole
• Pyrantel pamoate
• Albendazole

Targeted Therapy: Necator americanus

• Mebendazole
• Pyrantel pamoate
• Albendazole

• Mebendazole
• Pyrantel pamoate
• Albendazole

• Mebendazole
• Pyrantel pamoate
• Albendazole

Broad spectrum antihelminthic action

• Single day treatment, TID
• CYP450 Metabolism -- possibility for drug interactions
• Lack of serious toxicity
• Take with liquid at meals

Inhibits polymerization of tubulin into microtubules of helminths --> depletes glycogen stores --> decrease in ATP

• Hepatotoxic (caution with liver disease)
• Poorly absorbed systemically
• May cause abdominal pain, nausea, vomiting, or headache

• The only OTC medicine to treat pinworms
• Repeat dose in 2 weeks -- only kills the adult pinworms, NOT the eggs -- give again in 2 weeks because the eggs can survive and become adults
• Caution with liver disease

• Attach to or live on the skin
• Directly damage the host or indirectly by depositing feces, saliva, or pathogen
• At the site of the bite, mouthparts may be associated with lymphocytes, eosinophils, macrophages which is a response to what is being deposited (feces, saliva, pathogen)

• Chitinous exoskeleton (cuticle)
• The exoskeleton limits growth so periodic molting is required

• Causes paralysis of the louse or mite
• Indicated for lice, ticks, mites, and fleas

• Only indicated for patients that have failed first line treatment (permethrin)
• Black Box Warning: Seizures and deaths with repeat or prolonged application -- should not be given to children who weigh < 110 lbs because it increases risk of neurotoxicity