Antiparasitics

Question 1

Prevalence in the USA

Answer 1

Helminth Infections 
Toxocara 
Malaria
Amebiasis
Giardia
Trichomonas vaginalis
Infections associated with poor economic conditions

Question 2

Approach to Antiparasitic Chemotherapy

Answer 2

Target enzymes/function unique to parasite
Target enzymes indespinsable to them
Target common functions but different pharmacological properties

Question 3

Chemotherapy of Nematode (Roundworm) Infections

Answer 3

Mebendazole
Albendazole
Thiabendazole
Pyrantel Pamoate

Question 4

Mebendazole

Answer 4

Poor oral absorption 
Intestinal roundworms
Kills som Ova
Broad coverage
Poorly absorbed; low systemic toxicity

Question 5

Albendazole

Answer 5

Echnococcus
Unlableled use: cutaneous larval migrans
Well distributed
Elevated hepatic enzymes, abdominal pain, nausea, vomiting, headache

Question 6

Pyrantel Pamoate

Answer 6

Hookworm, pinworm, and roundworm
OTC as Pin-X for pinworm
Not for whipworm (Trichuris)
Poorly absorbed so for mild GI symptoms

Question 7

Thiabendazole

Answer 7

Strongyloides, cutaneous larva migrans (“disseminated” dog or cat hookworm)
oral or topical if limited
Rapidly absorbed: nausea, vomiting, dizziness

Question 8

Trematode Infections

Answer 8

Praziquantel

Question 9

Praziquantel

Answer 9

Drug of choice for Schistosoma
Some activity against other trematodes
Good activity for Cestodes
Taenia solium also kills eggs (which are infective to man) therby avoiding cysticercosis (PREVENTIVE FOR NEUROCYSTOCERCOSIS)
Side effects: abdominal discomfort, nausea

Question 10

Cestode (tapeworm) Infections

Answer 10

Praziquantel
Albendazole
Paromomycin Sulfate

Question 11

Albendazole

Answer 11

Cestode Infections
Systemically distributed
Treat neurocysticercosis

Question 12

Paromomycin Sulfate

Answer 12

3rd choice for those who can’t tolerate the other drugs

Treats Cestode Infections

Question 13

Antimalarial Drugs

Answer 13

None are preventive of infection

Only prevent progression to systemic malaria (prophylaxis)

Question 14

Prophylaxis

Answer 14

For P.vivax and ovale target hepatic form for 14 days after leaving endemic area
For all 4 species, target RBC forms whilein endeic area and continue for 4 weeks after leaving endemic area

Question 15

Chloroquine

Answer 15

First effective synthetic antimalarial
Basic drug in acidic vacuole of parasite
Parasitized erthrythrocytes concentrate the drug (by pH mechanisms)
Inhibits the heme polymerization allowing heme to accumulate to toxic levels and damage the parasite
Uses: malarial prophylaxis (all 4 species if they are sensitive) but not as effective for chloroquine-resistant strains of P. falcipairum and P. vivax
Treatment to eradicate P. malariae and chloroquine sensitive P. falciparum and Target blood schizonts of P. vivax and ovale (doesn’t target liver hypnozoites)
Side Effects: visual impairment

Question 16

Mefloquine

Answer 16

Mechanism: similar to chloroquine
against blood schizonticide
Use: treatment of chloroquine resistant P. falciparum and P. vivax
prophylaxis in chloroquine resistant areas
Contrainidcated: epilepsy and psychiatric disorders
Side effects: psychiatric effects (anxiety, paranoia, depression) and vestibular effects (dizziness, vertigo)

Question 17

Atovaquone and Proguanil (malarone)

Answer 17

Both block pyrimidine synthesis
Atovaquone- selectively inhibits malarial mitochondrial electron transport (cytochrome bc1) and disrupt pyrimidine synthesis
Proguanil- inhibit malarial dihydrogolate reductase and block folate synthesis
Use: prevention and treamtent of chloroquine resistant P. falciparum
Side Effects: nausea, diarrhea, vomitin, rash

Question 18

Quinine

Answer 18

Similar to chloroquine
Use: blood schizonticide: all four malarial parasites
severe acute attacks
alternative for chloroquine resitant P. falciparum
Side Effects: cinchonism (headache, visual disturbance, dizziness, tinitus), gastric irritaiton, nausea, vomiting, cardiac effects like quinidine

Question 19

Doxycycline

Answer 19

Antimalarial mechanisms: decrease malarial protein synthesis, depresses dihydoorotate dehydrogenase activity (interfere with pyrimidine synthesis)
Use: treat of multidrug resistant P. falciparum and prophylaxis of chloroquine resistant P. falciparum

Question 20

Primaquine

Answer 20

Uses: kills liver hypnozoites, radical cure/terminal prophylaxis of P. vivax and P. ovale (in conjunction with blood schizonticide)
pneumocystis jivoreci pneumonia in AIDA patients in combination with clindamycin
Side Effects: hemolytic reactions in those with G6P dehydrogenase deficiency

Question 21

Therapy of Amebic Dysentery

Answer 21

Tissue Amebicides- metronidazole (symptomatic infections)

Lumnial amebicides- iodoquinol, paromomycin suflate (alone for asymptomatic infections and given with tissue amebicide)

Question 22

Metronidazole

Answer 22

Tissue amebicide
Symptomatic infections
Giardia lamblia
Trichomonas Vaginalis

Question 23

Iodoquinol

Answer 23

Luminal amebicide

Side Effects :diarrhea, other GI symptoms, contraindicated in those with hypersinsitive to iodine

Question 24

Paromomycin SUlfate

Answer 24

luminal amebicide
aminoglycoside that inhibits protein synthesis
oral dose is poorly absorbed= low incidence of systemic side effects
Side effects: diarrhea, nausea, vomiting, epigastric pain

Question 25

Nitazoxanide

Answer 25

Giardia lamblia Cryptosporidium parvum GI side effects: diarrhea, nausea, abdominal pain Inhibits pyruvate: ferredoxim oxidoreductase, disrupting anaerobic energy metabolism

Question 26

Atovaquone

Answer 26

Pneumocystis jivoreci (carinii) prophylaxis or treatment Toxoplasma gondii Used with proguanil- prevention and treament of chloroquine resistant P. falciparum

Question 27

Treatment of Pneumocystis Jivoreci

Answer 27

Trimethoprim+suflamethoxazole (TMP-SMX) Clindamycin+ primaquine Atovaquone Dapsone