Antihelminthic Flashcards
What is unique about the lifecycle of worms?
Multiply outside of their hosts - killing adults in host leads to permanent reduction of worm burden.
Exceptions: Strongyloides, Echinococcus.
Name 6 Intestinal Roundworms and their sources.
- Enterobius vermicularis (pinworm)- Food w/ eggs
- Ascaris lumbricoides (giant round) - Fecal-oral eggs
- Strongyloides stercoralis (thread) - Larvae penetrate skin
- Necator/Ancylostoma (hook) - Larvae penetrate skin
- Trichuris trichura (whip) - Food w/ eggs
- Trichinella spiralis - Larvae in undercooked pork
MNEUMONIC: Ryan had 2 TRICHS played on him and he got ASCARe and ROLLED (roundworm) his ankles even through he had STRONG ANCYLs. This gave him ENTERic problems (enterobius and intestinal roundworms).
Medications for Intestinal Roundworms
Bendazoles, pyrantel pamoate, Ivermectin (strongyloides)
Name 4 Tissue Roundworms and their transmission.
- Dracunculus medinensis - Drinking water
- Onchocerca volvulus - Female blackfly
- Loa loa - Deer, horse, and mango flies
- Wuchereria bancrofti - Female mosquito
- Toxocara canis/cati - Food w/ eggs
Name 4 tapeworms (cestodes) and their transmission.
- Taenia saginata - larvae undercooked beef
- Taenia solium - larvae undercooked prok
- Diphyllobrothrium latum - Larvae freshwater fish
- Echinococcus granulosus - Eggs dog feces
Which is the largest tapeworm?
Diphyllobrothrium latum - 10m
What is the main problem with Taneia solium infections?
Neurocysticercosis. Ingest oncospheres –> hatch –> invade and migrate into mm, brain, liver –> cysticerci
Name 3 trematodes (flukes) and their transmission.
Schistosoma - snails
Clonorchis sinensis - undercooked fish
Paragonimus westermani - undercooked crab
What causes the symptoms associated with bloodflukes (schistosoma)?
Immune reaction with eggs.
Headache, fatigue, fever, GI problems, Hepatic fibrosis, ascites, bladder cancer.
What drug is used for flatworms? What is the one exception?
Praziquantel - for cestodes and trematodes.
Except - Echinococcus granulosus - use bendazoles.
What is the most common worm infection in the world?
Ascarasis. Associated with poor sanitation.
What two worms are associated with undercooked pork?
Taenia solium - Intestinal and neural stage
Trichinella spiralis - Intestinal and mm stages
What is one major sign of filariasis?
Elephantiasis from lymphatic dwelling.
What is the main goal of helmnith therapy?
Reduce the worm burden.
What is the mechanism of Praziquantel? What do you treat with this?
Disrupts clacium homeostasis –> mm spasms –> dislodge and kill worms
Treat Flatworms (trematodes, cestodes)
What is the mechanism of Benzimidazoles? What are three examples?
Bind microtubule + end and prevents growth. Shortening continues from the - ends.
Examples: Albendazole, Mebendazole, Thiabendazole
A fatty meal needs to be taken with what anti-helminthic medication and why?
With ALL benzimidazoles WHEN TREATING TISSUE INFECTIONS - needed to enhance tissue uptake of the medication.
For luminal infections - take on an empty stomach
Why would you use Albendazole over Mebendazole?
Albendazole:
- Also treats cystercosis (cestode) in addn. to Intestinal nematodes
- CAN be used in pregnancy
- Activated in liver (less toxicity/less excretion impairment if liver damage)
When would you use Thiabendazole?
Never - toxicity, Can’t be used in pregnancy.
What is Diethylcarbamazine used to treat? What might you co-administer and why?
Filariasis: Loa Loa, Wurchereria bancrofti (drug of choice)
Possibly with doxycycline: Kill Wolbachia encosymbiont
What is the Mazzotti reaction? When is this seen?
An immune reaction to dying worms: Papular rash, itching, enlarged lymph nodes, fever, arthralgias.
Seen especially in filiarial diseases, particularly Onchocerca volvulus.
What is Ivermectin used to treat? What is its mechanism of action?
Strongyloides and Onchocerca.
Paralyzes parasites by binding Cl- ion channels - ENHANCES GABA signaling.
What drug is sometimes used in mass treatment programs - e.g. in school children?
Ivermectin - because larvae in soil penetrate skin for Strongyloides
What is Pyrantel pamoate used to treat?
Broad spectrum
Alternative to Benzimidazoles for Enterobius, Ascaris, and Necator/Ankylostomata
What is the mecahnism of pyrantel pamoate? What anti-helmnithic is it similar to and how do the two differ?
Both ivermectin and pyrantel pamoate work on neurotransmitters to paralyze and expel the organism.
Pyrantel pamoate causes Ach release and Cholinesterase inhibition.
What is the treatment for head lice and scabies?
permethrin w/ 2nd application 10 days following
pre treat scabies w/ salicyclic acid if crusted
