S1B6 - Antiparasitics Flashcards
What is the mechanism of action of quinoline derivatives in malarial infection? What are some examples of quinoline derivatives?
Quinoline derivatives have activity against the erythrocytic stage of infection. Quinoline derivatives function to block the detoxification of heme into hemozoin. Heme accumulates and is toxic to plasmodia. Quinoline derivatives include
- Chloroquine
- Mefloquine
- Primaquine
- Quinine
What antimalarial has the fastest parasitic clearance of all antimalarials currently used? How is this drug used as part of an antimalarial regimen?
Artemisinins such as artesunate act by binding iron, breaking down peroxide bridges that lead to the generation of free radicals. Artemisinins have the fastest parasite clearance times of any antimalarial and act rapidly, killing blood stages of all Plasmodium species. Artemisinin-based combination therapy (ACTs) combine the highly effective short-acting artemisinins with a longer-acting partner to protect against artemisinin resistance and to facilitate dosing convenience.
Acute malarial attack caused by chloroquine resistant P. vivax could be treated with
A) Chloroquine
B) Quinine and Doxycycline
C) Quinine
D) Primaquine
Quinine and Doxycycline
A 16-year-old male with copious volume watery diarrhea after a camping trip is suspected of having a Giardia infection. Which antibiotic should be prescribed?
A) Piperacillin-tazobactam
B) Metronidazole
C) Gentamicin
D) Polymyxin B
E) Ciprofloxacin
Metronidazole
Answer Explanation
Metronidazole is used for some protozoal infections, notably Giardia and Entamoeba.
Match bugs to drugs; What drugs can be used for Giardiasis? (treatment is typically monotherapy with one of them)
Drugs for Giardiasis
- metronidazole
- tinadazole
- nitazoxanide
Ivermectin
A) inhibits beta-tubulin polymerization
B) causes paralysis of the pharyngeal muscles of worm by activating glutamate-gated channels
C) causes paralysis of the pharyngeal muscles of worm by activating GABA-gated chloride channels
D) causes paralysis of the pharyngeal muscles of worm by activating glutamate-gated chloride channels
causes paralysis of the pharyngeal muscles of worm by activating glutamate-gated chloride channels
Match drugs to bugs; In Africa, a patient with G6PD and with Ascariasis is treated with
A) mebendazole
B) praziquantel
C) metronidazole
D) primaquine
E) atovaquone/proguanil
mebendazole
What species of Plasmodium is mefloquine effective against?
Mefloquine is available as an oral formulation and may be used as treatment or prophylaxis for P. falciparum (including choloroquine-resistant strains) or P. vivax.
Treating chloroquine resistant P. plasmodium, an appropriate drug is
A) chloroquine
B) atovaquone/proguanil
C) primaquine
D) metronidazole
E) mebendazole
atovaquone/proguanil
In treating malaria, it is important to know wheter it is
A) chloroquine resistant
B) P. vivax or P. plasmodium
C) Both of the above
Both of the above
Describe 6 clinical indications for metronidazole.
Metronidazole indications can be remembered by the mnemonic GET GAP on the Metro:
- Giardia
- Entamoeba
- Trichomonas
- Gardnerella vaginalis
- Anaerobes (Bacteroides, C. difficile)
- H. Pylori (as part of triple therapy with proton pump inhibitor and clarithromycin)
Menbendazole
A) is a prodrug activated by a parasite’s enzyme
B) is poorly absorbed by the host (human)
C) is selectively toxic to the parasite and not the host (human)
D) is absorbed by host (human) and toxicity is an importand issue
is poorly absorbed by the host (human)
Is lindane first line or second line in the treatment for scabies?
Lindane is indicated for patients who cannot tolerate or have failed first-line medication for the treatment of scabies.
What are the indications for permethrin?
Permethrin is often used to treat head lice and scabies.
Ascaris lunbricides (Giant round worm) infection could be treated with
A) Mebendazole
B) Malathion
C) Metronidazole
D) Nitozoxanide
Mebendazole
How do antifolates function in treating Plasmodium infections? What are some examples of antifolates that can serve as antimalarials?
Antifolates act synergistically to target enzymes involved in folate synthesis, which leads to impairment of parasite DNA synthesis. Examples of antifolates used for malaria include
- Sulfonamides
- Pyrimethamine
- Proguanil
- Dapsone
Which foods should not be taken with metronidazole?
A) Fava beans
B) Unpasteurized cheese
C) Grapefruit
D) Alcohol
Alcohol
Answer Explanation
Metronidazole + EtOH can lead to an unpleasant disulfiram-like reaction (nausea, flushing).
What is the mechanism of action of permethrin?
Permethrin is an antiparasitic agent that works by inhibition of sodium ion influx through cell membrane channels in parasites, resulting in delayed repolarization and thus paralysis and death of the pest.
Match bugs to drugs; fish tape worm is treated with
A) ivermectin
B) amphotericin B
C) mebendazole
D) praziquantel
praziquantel
Antimalarial drugs are similar in targeting what stage of malaria infection?
Antimalarial drugs are used for the treatment and prevention of malaria infection. Most antimalarial drugs target the erythrocytic stage of malaria infection, which is the phase of infection that causes symptomatic illness.
Which four drugs can be used for Amebiasis? (treatment is typically monotherapy with one of them)
Drugs for Amebiasis
- iodoquinol
- paromomycin
- metronidazole
- tinadazole
What species of Plasmodium is chloroquine ineffective against? What are the toxicities associated with chloroquine?
Chloroquine is use for the treatment of plasmodial species other than P. falciparum due to widespread resistance via a membrane pump that decreases intracellular concentration of the drug. Toxicities of chloroquine include retinopathy and pruritus (especially in dark-skinned individuals).
What is a common antifolate drug combination used for Plasmodium infections?
Atovaquone-proguanil interferes with two separate pathways involved in the biosynthesis of pyrimidines essential for nucleic acid replication.
What is the mechanism of action of lindane?
Lindane is an antiparasitic agent that is directly absorbed by parasites and ova through the exoskeleton and stimulates the nervous system by inhibition of GABA channels, resulting in seizures and death of parasitic arthropods.
What is the mechanism of action of malathion?
Malathion is an organophosphate that acts as a pediculicide by inhibiting cholinesterase activity in Pediculus humanus capitis (head lice).
What is the mechanism of action of metronidazole?
Metronidazole contains a nitro group that acts as an electron sink, capturing electrons and creating free radicals, resulting in cytotoxic intermediates that inhibit bacterial DNA synthesis.
What antimalarial is used for its effect on the latent hypnozoites in P. ovale and P. vivax infection?
Primaquine is used for infection due to P. ovale or P. vivax, due to its activity against hypnozoites, which can otherwise remain dormant in the liver for months to years after infection.
What are the toxicities associated with metronidazole?
Toxicities of metronidazole include
- Disulfiram-like reaction (severe flushing, tachycardia, hypotension) with alcohol
- Metallic taste
- Headache
