Antiparasitics Flashcards
What are the Antiamebics?
Metronidazole, Tinidazole, Diloxanide Furoate, Iodoquinol, Paramomycin, Chloroquine, Dehydroemetine, Emetine
Mixed Luminal and Systemic Antiamebics
Metronidazole and Tinidazole
DOC for invasive amebiasis
Metronidazole; follow with Luminal Agent
MOA of Metronidazole
Non-ezymatic reduction by Ferredoxin produces cytotoxic compounds that bind to proteins and DNA, causing cell death
Clinical applications of Metronidazole
Part of combination therapy against H. pylori, Giardia lamblia, Trichomonas vaginalis, Anaerobic cocci, Anaerobic Gram negative bacilli
PK of Metronidazole
Oral; well distributed (including vaginal and seminal fluids, CSF, breast milk, and saliva); hepatic oxidation and glucuronidation via CYP450 enzymes
AE of Metronidazole
Disulfiram-like reaction, dark urine, metallic taste, oral monoliasis, ataxia
Is Metronidazole safe for use during pregnancy?
Unknown
2nd generation Nitroimidazole better tolerated than Metronidazole
Tinidazole
Clincal applications of Tinidazole
Amebiasis, Amebic liver abscess, Giardiasis, and Trichomoniasis
AE of Tinidazole
Same as Metronidazole but shorter duration; dark urine, metallic taste, Disulfiram-like reaction, oral monoliasis, ataxia
Luminal Antiamebics
Diloxanide Furoate, Iodoquinol, Paramomycin
DOC for asymptomatic amebiasis
Diloxanide Furoate
MOA of Diloxanide Furoate
Converted to Diloxanide freebase active form in gut
AE of Diloxanide Furoate
Mild GI distress
Used as alternative to Diloxanide Furoate for mild to severe amebic infections
Iodoquinol
MOA of Iodoquinol
Orally active against luminal trophozoite AND cyst forms of E. histolytica
AE of Iodoquinol
Optic neuritis with long-term use; rash, diarrhea, peripheral neuropathy
Aminoglycoside antibiotic active against luminal forms of E.histolytica and tapeworm
Paramomycin
Clinical applications of Paramomycin
Alternative for Cryptosporidiosis in AIDS patient
MOA of Paramomycin
Amebicidal; binds to 30S ribosomal subunit to inhibit bacterial protein synthesis; reduces intestinal flora
AE of Paramomycin
Arthralgia, GI effects and diarrhea, headaches
Systemic Antiamebics
Chloroquine, Emetine, Dehydroemetine
Indications for Systemic Antiamebics
Treating liver abscesses or intestinal wall infections
Clinical applications of Chloroquine
Used in combination with Metronidazole and Diloxanide Furoate
MOA of Chloroquine
Eliminates trophozoites in liver abscesses
MOA of Emetine and Dehydroemetine
Block ribosomal movement along mRNA to inhibit protein synthesis
Indications of Dehydroemetine and Emetine
Backup drugs for treatment of severe intestinal or hepatic amebiasis
Clinical applications of Dehydroemetine and Emetine
Used in combination with luminal agent
PK of Dehydroemetine and Emetine
Concentrate in liver –> persist for 1 month; slow metabolism and elimination
AE of Dehydroemetine and Emetine
Pain at injection site, Cardiotoxicity, neuromuscular weakness, rash
Antihelminthics
Albendazole, Mebendazole, Thiabendazole, Ivermectin, Piperazine, Pyrantel pamoate, Diethylcarbamazine, Doxycycline, Praziquantel, Bithionol, and Niclosamide
Benzimidazole Antihelminthics
Albendazole, Mebendazole, and Thiabendazole
GABA Agonist Antihelminthics
Ivermectin and Piperazine
MOA Albendazole and Mebendazole
Inhibit microtubule synthesis and glucose uptake –> decreased ATP causes worm immobilization and death
Indications for Albendazole
Cestodal infections (cysticercosis), Taenia solium, Echinococcus granulosus (hydatid
PK of Albendazole
Oral; absorption enhanced by fatty meal;
Extensive first-pass metabolism –> rapid sulfoxidation to active metabolite
AE of Albendazole
Hepatotoxicity, agranulocytosis, or pancytopenia with long-term treatment (3 months for Echinococcus)
Which Benzimidazole is associated with inflammatory responses to dying parasites in the CNS?
Albendazole; convulsions, hyperthermia, headache, mental changes
Contraindications of Albendazole
Pregnancy (Cat. C) and children < 2 yoa
PK of Mebendazole
Oral; insoluble in aqueous solution; absorption increases with fatty meals; 1st pass metabolism causes inactive compounds
How are parasites treated with Mebendazole excreted?
In the feces
Contraindications of Mebendazole
Pregnancy (Cat. C) and patients with cirrhosis, and children < 2 yoa
AE of Mebendazole
abdominal pain, headache, diarrhea, and dizziness
MOA of Thiabendazole
Inhibits microtubule aggregation
Indications of Thiabendazole
Strongyloides stercalis (threadworm), cutaneous larva migrant, and early stage of trichinosis
PK of Thiabendazole
Oral; insoluble in water
Contraindications of Thiabendazole
Pregnancy (Cat. C), liver or kidney disease
AE of Thiabendazole
CNS disturbances (dizziness and seizures), Stevens-Johnson syndrome, Erythema multiforme
Most toxic of Benzimidazoles
Thiabendazole
DOC for Strongyloides, Onchocerciasis, and Cutaneous Larva Migrans
Ivermectin
MOA of Ivermectin
GABA agonist; Cl- influx causes hyper polarization of nerve/muscle cell –> paralysis of parasite causes death
PK of Ivermectin
Oral; does not cross BBB
Mazzotti-like Rxn is associated with which GABA agonist ?
Ivermectin
Contraindications of Ivermectin
Pregnancy (Cat. C), Meningitis (may cross BBB), and concomitant use with other GABAergic drugs (benzodiazepines and barbituates)
Contraindications of Piperazine
Patients with seizure disorders
MOA of Piperazine
GABA agonist
Indications of Piperazine
Alternative treatment for pinworm and round worm infections
PK of Piperazine
Expulsion of worm via peristalsis
Indications of Pyrantel pamoate
Roundworm, pinworm, and hookworm infections
MOA of Pyrantel pamoate
Acts as a depolarizing neuromuscular blockade –> Act release and inhibition of Achesterase causes persistent activation of parasite’s nicotinic receptors
PK of Pyrantel pamoate
Poor oral absorption –> exerts effects in intestinal tract
AE of Pyrantel pamoate
N/V/D
MOA of Diethylcarbamazine
Immobilizes microfilariae, making them susceptible to host defenses
DOC for Loiasis, Tropical Eosinophilia, and Lymphatic filiarisis
Diethylcarbamazine
May administer Antihistamines or Steroids with this Antihelminthic agent to decrease AE
Diethylcarbamazine
AE of Diethylcarbamazine
Thought to be due to host responses after damage to/death of parasite: leukocytosis, myalgia, fever, rash, etc.
Tetracycline antibiotic that also is active against Wucheria bancrofti (macrofilaricidal) and Onchocerca volvulus (onchocerciasis)
Doxycycline
MOA of Doxycycline
Acts indirectly by killing Wolbachia, intracellular bacterial symbiont of filarial parasites
Which Antihelminthic drug has the same efficacy as Albendazole when treating Cysticercosis?
Praziquantel
DOC for Schistosomiasis and most Trematode and Cestode infections
Praziquantel
MOA of Praziquantel
Increases cell membrane permeability to Ca ==> contracture and paralysis of worm musculature ==> detachment of suckers from blood vessel walls
PK of Praziquantel
Oral; extensive first-pass metabolism via CYPs
Excretion of Praziquantel
Inactive metabolites excreted in bile and urine
Drug interactions with Praziquantel are due to?
CYP450 enzymes
Contraindications of Praziquantel
Pregnancy (Cat. B), nursing mothers, treatment of Ocular Cysticercosis (destruction of organism may damage the eye!)
AE of Praziquantel
GI upsets, anorexia, drowsiness
DOC for Fasciolis (sheep liver fluke)
Bithionol
Alternative treatment for Pulmonary Paragonimiasis
Bithionol
MOA of Bithionol
Inhibits parasite’s ETC
2nd line drug for most Cestode infections; however, it is uncommonly used due to efficacy of Praziquantel
Niclosamide
MOA of Niclosamide
Inhibits mitochondrial phosphorylation of ADP and possibly inhibits anaerobic metabolism
How does Niclosamide affect Cestodes?
Lethal to Cestode scolex and segments of Cestode but not to ova
PK of Niclosamide
Oral; Laxative should be administered prior to Niclosamide purge all dead segments and ova, which may lead to Cysticerosis
What must be avoided within 1 day of dose of Niclosamide
Alcohol
Is Niclosamide safe for use in pregnancy and children < 2 yoa?
Unknown
DOC for Ascariasis (roundworm)
Albendazole, Pyrantel pamoate, or Mebendazole
DOC for Enterobiasis (pinworm)
Mebendeazole or Pyrantel pamoate
DOC for Trichuriasis (whipworm)
Mebendazole or Albendazole
DOC for Hookworm (N. americanus or A. duodenale)
Pyrantel pamoate, Mebendazole, or Albendazole
DOC for Onchocerciasis (River Blindness)
Ivermectin
Cutaneous larva migrans (Creeping eruption, dog, and cat hookworm) Ancylostoma sp
Albendazole or Ivermectin
DOC for Fasciola hepatica (liver fluke)
Bithionol
DOC for Schistosomiasis
Praziquantel
DOC for Clonorchis sinensis (Oriental liver fluke)
Praziquantel
DOC for Paragonimus westermani (lung fluke)
Praziquantel
DOC for Echinococcosis - Echinococcus granulosis (dog tapeworm)
Albendazole
DOC for Taeniasis - Taenia solium (pork tapeworm)
Praziquantel or Niclosamide
DOC for Taeniasis - Taenia saginata (beef tapeworm)
Praziquantel or Niclosamide
Cysticercosis (Taenia solium larvae)
Albendazole or Praziquantel
DOC for Dyphyllobothriasis - Dyphyllobothrium latum (fish tapeworm)
Praziquantel or Niclosamide
DOC for Giardia lamblia and Trichomonas vaginalis
Metronidazole
Trypanosomiasis (African sleeping sickness)
Melarsoprol or Suramin
Treatment of hemolymphatic stage of trypanosomiasis and for Pneumocystis jiroveci
Pentamidine
DOC Toxoplasmosis (toxoplasmic encephalitis)
Pyramethamine + Clindamycin or Sulfadiazine or Folinic acid (Leucovorin)
Treatment of Leishmaniasis (all stages)
Sodium stibogluconate/Amphotercin B
DOC for Pneumocystis jiroveci
Trimethoprim-Sulfamethoxazole (Cotrimoxazole)