Anti-Parasitic Drugs (Buxton) Flashcards
Plasmodium sp., Giardia lamblia, Entamoeba histolytica, and Toxoplasma gondii are all examples of what kind of organism?
Protozoa
Schistosoma sp. is an example of what kind of organism?
Trematode
Teania sp. is an example of what kind of organism?
Cestode
Ascaris lumbricoides, hookworms, Trichinella sp., and filarial worms are all examples of what kind of organisms?
Nematodes
A 25-year-old medical student presents with high fever and chills, severe headache, malaise and myalgia 4 days after returning from a medical mission trip to Nigeria. He took chloroquine prophylactically to prevent malaria. His blood smear is shown in the photo. What does his blood smear show and how should he be treated?
P. falciparum (banana-shaped gametocyte)
Artemisinin
What happens when plasmodium break down heme?
Plasmodia utilize amino acids from hemoglobin; leaving behind heme, which becomes very toxic when it accumulates in the cell.
What treatments for malaria are inhibitors of the parasite electron transport system?
Atovaquone
Primaquine
What treatments of malaria are inhibitors of heme metabolism?
Chloroquine
Quinine
Qunidine
Mefloquine
Artemisin
What do inhibitors of heme metabolism do?
Result in build-up of toxic heme metabolites which are lethal to the parasite
What treatments of malaria inhibit translation?
Tetracycline
Doxycycline
Clindamycin
What do inhibitors of translation for the treatment of malaria do?
Bind to 30S or 50S ribosomal subunit to prevent parasite protein synthesis
What treatments of malaria inhibit folate metabolism?
Sulfdoxine + Pyrimethamine
Proguanil
What do inhibitors of folate metabolism for the treatment of malaria do?
Inhibit parasite nucleotide synthesis
Which drugs are used for the prevention of malaria?
Atovaquone/Proguanil
Chloroquine
Doxycycline
Mefloquine
Primaquine
What does malaria treatment depend on?
Species and resistance patterns in the geographic region where the infection occurred
What can sensitive strains of all 4 species of Plasmodium be treated with?
Chlorquine or Hydroxychloroquine
What drug must be added to the treatment regimine for P. vivax and P. ovale? Why?
Primaquine - hypnozoites
What can be used to treat Chloroquine-resistant P. falciparum?
Atovoquone-probuanil
A 25-year-old medical student is planning a mission trip to Uganda. Among the infectious disease precautions she must consider is prophylaxis for malaria.
Which malarial parasites are found in Uganda?
P. falciparum (>85%); P. malariae, P. ovale, P. vivax make up the remainder
A 25-year-old medical student is planning a mission trip to Uganda. Among the infectious disease precautions she must consider is prophylaxis for malaria.
Which drugs are available for malria prevention? What are their mechanisms of action?
Atovaquone-proguanil - inhibits ETC; inhibits folate metabolism
Doxycycline - inhibits translation
Mefloquine - inhibits heme metabolism
A 33-year-old male presents with high fever and shaking chills. He had recently returned from a 2-month long mission trip to India. He had taken malaria prophylaxis (Atovaquone-proguanil) while in India, but stopped the drug the day he left to return to the US (should be taken for 1 week after leaving malarious area). A blood smear taken to look for malaria parasites is shown. He is diagnosed with Plasmodium vivax.
How should this patient be treated? Justify choice of drugs.
Chloroquine + Primaquine
Must keep taking drugs after return because they’re killing parasite at different stages
What is used to treat chloroquine-resistant P. falciparum?
Mefloquine
Quinine + Doxycycline/Clindamycin
Atovaquone + Proguanil (aka Malarone)
What is used to treat Chloroquine-sensitive P. falciparum and P. malariae?
Chloroquine
What is used to treat P. vivax and P. ovale?
Chloroquine + Primaquine
A 12 year old boy presents with a 1 week history of malaise, weakness, abdominal cramps and diarrhea. Upon questioning, the boy admits to feeling bloated and having excessive flatulence. The stool is grey or light colored and greasy or fatty in appearance (steatorrhea) and is not visibly bloody. He had recently returned from a week long camping trip, and admits to drinking from a stream in the area. Examination of the stool reveals the parasite shown in the photograph.
With which parasite is he infected?
Giardia lamblia
A 12 year old boy presents with a 1 week history of malaise, weakness, abdominal cramps and diarrhea. Upon questioning, the boy admits to feeling bloated and having excessive flatulence. The stool is grey or light colored and greasy or fatty in appearance (steatorrhea) and is not visibly bloody. He had recently returned from a week long camping trip, and admits to drinking from a stream in the area. Examination of the stool reveals the parasite shown in the photograph.
How is this infection treated? What do these drugs do? What other parasitic infections are treated with the same agent?
Metronidazole
Nitazoxanide
Tinidazole
All 3 drugs induce DNA damage and generate toxic radicals within the parasite
Entamoeba histolytica, Trichomonas vaginalis
An ultrasound preformed on a pregnant woman in her 24th week of gestation showed her fetus to have hydrocephalis and intracranial calcifications. The mother was tested and found to have IgM antibodies to Toxoplasma gondii.
What is the recommended treatment for this infection?
What is the mechanism of action for these drugs?
Spiromycin - macrolide that binds to 50S ribosomal subunit to block protein sythesis
Pyrimethamine/sulfadiazine + leucovorin - 1st 2 are inhibitors of folate metabolism; leucovorin is a rescue antidote to prevent toxicity from either of the others
A 26-year-old Peace Core volunteer in Kenya was sent home due to 4 month history of increasing upper right quadrant abdominal pain, nausea, vomiting and diarrhea. Physical exam revealed hepatosplenomegaly. The stool was positive for blood. Stool cultures were negative for bacterial pathogens; however an ova and parasite exam revealed the eggs shown in the photo.
What kind of organisms are schistosomes?
Trematodes - blood flukes
A 26-year-old Peace Core volunteer in Kenya was sent home due to 4 month history of increasing upper right quadrant abdominal pain, nausea, vomiting and diarrhea. Physical exam revealed hepatosplenomegaly. The stool was positive for blood. Stool cultures were negative for bacterial pathogens; however an ova and parasite exam revealed the eggs shown in the photo.
How is this infection treated? What is the mechanism of action for this drug? What else can it treat?
Praziquantel
Increases parasite membrane permeability to calcium, resulting in parasite muscle contraction and paralysis
Can treat tapeworm & trematode infections, e.g. Echinoccus sp., Tania solium, Schistosoma sp.
While on a medical mission along the Amazon River in Peru, several children in a village present with varying degrees of abdominal discomfort. Ova and parasite exam results from stool are shown in the photographs.
With which parasites are they infected? What kind of parasites are these?
Nematodes - Ascaris, Ancyclostoma, Trichuris
While on a medical mission along the Amazon River in Peru, several children in a village present with varying degrees of abdominal discomfort. Ova and parasite exam results from stool are shown in the photographs.
What is the treatment for this infection? How do medications work?
Albendazole, Mebendazole, Thiabendazole
These drugs act by interfering with tubulin polymerization, leading to degradation of integument; also damages parasite intestinal epithelial cells
What, other than nematode infections, can albendazole, mebendazole, and thiabendazole be used to treat?
Cysticercosis & echinococcosis
What is pyrantel pamoate used to treat?
What is its mechanism of action?
Roundworms & hookworms
Acetylcholine agonist and depolarizing neuromuscular blocking agent. It produces rigid contraction of nematode muscles.
In the Garawan village, 60km north of Cairo, the WHO is attempting to reduce cases of lymphatic filariasis. The photos show individuals who developed symptoms of the disease at a young age and are now unable to stand or walk for long periods of time.
Which organisms cause lymphatic filariasis?
Lymphatic filariasis - Wuchueria bancrofti & Brugia malayi
Subcutaneous filariasis - Onchocerca volvulus, Loa loa
In the Garawan village, 60km north of Cairo, the WHO is attempting to reduce cases of lymphatic filariasis. The photos show individuals who developed symptoms of the disease at a young age and are now unable to stand or walk for long periods of time.
How is are these types of infection treated? What is the mechanism of action for these drugs?
Ivermectin - treatment of microfilariae of Onchocerca; increases cell membrane permeability for chloride ions, causing hyperpolarization of nerve or muscle cell, leading to paralysis
Diethylcarbamazine - similar to Ivermectin, but also kills adult worms
What drugs are used to treat Babesia microti?
Clindamycin + quinine
Atovaquone + azithromycin
What drugs are used to treat Toxoplasma gondii?
Spiromycin
Pyrimenthamine/sulfadiazine + leucovorin
What drugs are used to treat Giardia lamblia?
Metronidazole
Nitazoxanide
Tinidazole
