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25 terms

Medical Pharmacology - Antiparasitic Drugs (Test V)

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What are the three targets for antiparasitic chemotherapy?
1) Enzymes/processes found only in the parasite

2) Enzymes/processes found in both the host and parasite but indispensable only in the parasite

3) Common biochemical functions found in both parasite and host, but with different pharmacological properties
Metronidazole

Mechanism:
Spectrum:
Resistance:
Mechanism
- activated by PFOR (is NOT found in host cells)
- reactive intermediates disrupt protein and DNA
structure and function (an electron "sink")

Spectrum
- Trichomoniasis (*treat sexual partner too!),
Giardiasis, Amebiasis

Resistance
- rare
- due to DEC PFOR activity
What is the drug of choice for the treatment of Giardia lambia, Entamoeba histolytica, and Trichomonas vaginalis?
Metronidazole
Which drugs are the primary choice for the treatment of asymptomatic carriers of E. histolytica?
Iodoquinol and Paromomycin
Iodoquinol

Mechanism:
Spectrum:
Resistance:
Mechanism
- eliminates trophozoite and cyst forms of E.
histolytica from the LUMEN (not in tissue)

Spectrum
- asymptomatic/mild amebiasis (20 day regimen)

Resistance
- none
Paromomycin

Mechanism:
Spectrum:
Resistance:
Mechanism
- inhibits protein synthesis
- eliminates trophozoite and cyst forms of E.
histolytica from the LUMEN (not in tissue)

Spectrum
- asymptomatic/mild amebiasis

Resistance
- none
Nitazoxanide

Mechanism:
Spectrum:
Resistance:
Mechanism
- interference with PFOR

Spectrum
- Cryptosporidium parvum and Giardia lamblia
(OPPORTUNISTIC)

Resistance
- none
Pyrimethamine-Sulfadiazine AND
Trimethoprim-Sulfamethoxazole

Mechanism:
Resistance:
Mechanism
- inhibit pteroic acid formation via
dihydroptheroate synthase
(sulfamethoxazole/sulfadiazine)
- inhibit DHFR (Trimethoptrim/Pyrimethamine)

Resistance
- widely reported
- due to amino acid substitutions (point
mutations)
What is the drug of choice for Cryptosporidium parvum infection in the HIV/AIDS population?
Paromomycin and Nitazoxanide
What is the drug of choice for the treatment of Pneumocystis jirovecii?
Trimethoprim-Sulfamethoxazole
What is the drug of choice for the treatment of Toxoplasma gondii (Toxoplasmosis)?
Pyrimethamine-Sulfadiazine
True or False

Pyrimethamine-Sufadiazine can treat both active and dormant tissue cysts during Toxoplasmosis
False (CANNOT destroy dormant tissue cysts)
Chloroquine

Mechanism:
Spectrum:
Resistance:
Mechanism
- eliminates asexual erythrocytic stages of ALL
Plasmodium stages
- interferes w/ parasite's ability to detoxify

Spectrum
- effective against ALL species of Plasmodium in
the asexual erythtocytic stages

Resistance
- rapid, widespread resistance
- due to INC efflux
Quinine

Mechanism:
Spectrum:
Resistance:
Mechanism
- interferes with transcription and replication
- targets the intraerythrocytic forms

Spectrum
- effective against ALL species of Plasmodium in
the asexual erythtocytic stages

Resistance
- beginning to emerge in Asia

**not used often due to TOXICITY
Which anti-malarial drug can lead to CINCHONISM (tinnitus, hearing loss, headache, N/V, and visual disturbances)?
Quinine

**also causes HYPOGLYCEMIA
Which anti-malarial drug drug of choice that is active against the LIVER (hypnozoite) forms of P. vivax and P. ovale?
Primaquine
Mefloquine

Mechanism:
Spectrum:
Resistance:
Mechanism
- targets the intraerythrocytic forms

Spectrum
- effective against ALL species of Plasmodium in
the asexual erythtocytic stages

Resistance
- none
Primaquine

Mechanism:
Spectrum:
Resistance:
Toxicity:
Mechanism
- interferes with ETC and pyrimidine synthesis

Spectrum
- treats dormant LIVER (hypnozoite) forms of P.
vivax and P. ovale

Resistance
- some have emerged (require repeated therapy
and INC dosage)

Toxicity
- hemolysis w/ G6PD deficiency (SCREEN!!)
Malarone

Mechanism:
Spectrum:
Resistance:
Mechanism
- inhibits DHFR

Spectrum
- highly efficacious in the treatment of P.
FALCIPARUM (as well as prophylaxis)

Resistance
- none
What is the drug of choice for the treatment of P. falciparum?
Malarone
Doxycycline

Mechanism:
Spectrum:
Resistance:
Mechanism
- inhibit protein synthesis and cell growth

Spectrum
- effective against all species of Plasmodium
(treatment and prophylaxis)

Resistance
- none
Benzimidazoles (Albendazole, Mebendazole, Thiabendazole)

Mechanism:
Spectrum:
Resistance:
Mechanism
- inhibits assembly of microtubules and disrupts
mitosis via binding to beta-tubulin

Spectrum
- Albendazole/Mebendazole = drugs of choice of
Ascariasis, Hookworm, Pinworm, and
Whipworm
- Thiabendazole = second line drug for
Strongyloidiasis, and topical for Cutaneous
Larval Migrans

Resistance
- occurs in veterinary medicine only
Ivermectin

Mechanism:
Spectrum:
Resistance:
Mechanism
- causes INC Cl permeability and muscle
paralysis
- mainly works on embryogenesis

Spectrum
- Strongyloidiasis, and other tissue dwelling
helminths

Resistance
- none
Pyrantel Pamoate

Mechanism:
Spectrum:
Resistance:
Mechanism
- produces depolarizing neuromuscular blockade
via cholinergic nicotinic receptor activation

Spectrum
- drug of choice for PINWORM
- **treat the ENTIRE househole

Resistance
- only in veterinary medicine
Praziquantel

Mechanism:
Spectrum:
Resistance:
Mechanism
- INC Ca permeability & cause depolarization

Spectrum
- drug of choice for nearly all TAPEWORM and
FLUKE infections

Resistance
- resistant Schistosomes are emerging