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Antiparasitics: Antihelminthic Drugs Flashcards

1
Q

Antiparasitic drugs

A

no vaccines available

  • resistance always a problem
  • commercial incentives not really there to make parasitic infections
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2
Q

what are some neglected parasitic infections?

A

Trypanosma Cruzi-> chaga’s disease 30,000 people infected

Taenia solium-> pork tapeworm, 1,000 hospitalizations a yr

Toxocara-> dog and cat roundwarms, 14% of U.S. population exposed, 70 people are blinded (mostly children)

toxoplasma gondi

trichomonas

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3
Q

toxocara is what kind of parasitic infection?

A

zoonotic

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4
Q

toxoplasma gondi

A

60 million infection chronically

  • new infectious in pregnant women can lead to birth defects
  • can be fatal in people with IC’s
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5
Q

trichomoas

A

sexually transmitted

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6
Q

parasitic infections associated with HIV in US?

A

pneumocystis jiroveci-Pneumonia
toxoplasma gondi- encephalitis
cryptosporidium- cryptosporidiosis (contaminated drinking water)

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7
Q

parasitic infections associated with HIV globally?

A

Malaria
Leishmania
trypanosoma cruzi- Chagas disease

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8
Q

what is the global burden of malaria?

A

300-500 million cases/year

  • lots of death, mostly african children less than 5
  • no vaccine
  • drug resistance widespread
  • new drugs needed urgently
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9
Q

Malaria: Plasmodium falciparum

A
  • most important
  • tropical regions of Africa
  • can infection type of red blood cell
  • 48 hour life cycle
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10
Q

Malaria: Plasmodium vivax

A

relapsing malaria-caused by hypnozoites in liver (infections smaller subset of red blood cells, erythrocytes)

  • sub tropics and temperate regions
  • 48 hour life cycle
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11
Q

Malaria: Plasmodium ovale

A

relasping, found in west africa

  • no dominant form
  • 48 hour life cycle
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12
Q

Malaria: Plasmodium knowlesi

A

24 hour life cycle (fastest)

zoonotic infections

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13
Q

life cycle of Malaria

A

infected mosquitos bites person-> injects sporozoites-> go to liver and undergo 1 round of replication in liver-> progeny merozoites go on to infect red blood cells-> in blood merozoites invade and undergo replication-> 48 hours later lyse RBC and invade other RBC.
-sexual stages produce gameocytes that are passed on to mosquitos

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14
Q

what stage do malaria drugs usually target?

A

RBC stages

  • don’t treat symptoms
  • mainly targets RBC replication
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15
Q

chemoprophylaxis

A

No drugs that kills sporozoites

  • can’t prevent infection
  • drugs can prevent development of symptoms
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16
Q

RX establishment infection

A

No single agent effective vs ALL liver and RBC stages-complete elimination of infection may require more drug

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17
Q

Schizonticides

A

tissue- act on liver forms

Blood-act on RBC forms

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18
Q

Liver classification

A

Exoerythrocytic schizonticides
Primaquine
Atovaquone
Artemisinins

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19
Q

Blood drugs

A 
chloroquine 
melfoquine
artemisinins
quinine
doxycycline 
clindamycin
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20
Q

prevention against malaria

A

bed nets
insect repellent
-insecticides
why kind of malaria is there

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21
Q

gametocides

A

kill sexual stages and prevent transmission to mosquitos

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22
Q

drugs for prevention

A

Chloroquine (Aralen and generic) hydroxychloroquine
-continue for 4 weeks after leave the area
Mefloquine(lariam)
Primaquine
Doxycycline

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23
Q

chloroquine resistant drug option?

A

atovaquone + Proquanil

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24
Q

Mefloquine

A

start 2 weeks early and 4 weeks after

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25
Primaquine
primarly P. vivax in area | -start 1-2 days prior and 7 days after
26
Doxycycline
start 1-2 days prior and continue 4 weeks after
27
Treatment options for malaria
- depends on the type (species) - where they were when they got infected (for drug resistance) - Clinical status of patient (other conditions, accompanying illnesses, pregnant)
28
Drugs for uncomplicated malaria? Chloroquine sensitive
Chloroquine and hydroxychloroquine
29
Drugs for uncomplicated malaria? chloroquine resistant
``` atovaquone+ Proguanil Artmether + lumefantrine Quinine sulfate Doxycycline, tetracycline, clindamycin melfoquine ```
30
drugs for severe complicated malaria?
Quinidine gluconate- IV - plus doxycycline or tetracycline - consult a cardiologist and experienced physician monitor - can have severe cardiac complications-if so stop drug
31
Artesunate
alternative if quinidine gluconate not available or not tolerated -IV only Has IND
32
Artemisinin
derived from Chinese wormwood - endoperoxide active group required for function - mechanism not clear but may involve toxic free radicals - most likely interaction with intracellular iron in parasite - loss in mitochondrial potential possibly
33
advantages of artemisinin
- acts very quickly on blood schizonticide - 4 log reduction in parasite numbers in 48 hours - active against all species - no effect on liver stage
34
what species is artemisinin used for?
Chloroquine resistant P. falciparium
35
disadvantage of artemisinin?
short half life - recrudescence rate is high after short course of treatment - not good for chemoprophylaxis - commonly paired with other drugs (mefloquine or lumefantrine)
36
artemisinin combination therapy?
pairing of artemisinin derivatives with longer half life drugs - provides rapid knockdown - longer half life component eliminates remaining parasites - Artemisinin better tolerated than most anti-malarials
37
artemisinin combination drugs
artemether+ lumefantrine artensunate+ mefloquine dihydroartemisinin+ piperaquine
38
artemisinin anti-malarial effect associated with Cmax?
concentration dependent killing
39
artemisinin derivatives
Artesunate: water soluble Artemether:lipid soluble
40
adverse side effects of aretmisinin?
N&V, diarrhea, and dizziness | Not recommended for 1st trimester for uncomplicated malaria
41
quinolines
2 classes: 1. ) chemical substituent at 4 position 2. ) chemical substituent at 8th position
42
quinolines derivatives function
blocking polymerization of heme, accumulates in food vacuoles (pigment vacuole) and inhibits heme polymerization
43
hemoglobin metabolism in parasites
-parasites will ingest the hemoglobin and degrade it in order to produce amino acids-> once they degrade hemoglobin and release heme-> free heme is toxic-> parasites polymerize heme into hemozoin with is nontoxic
44
resistance of quiolines?
associated with lack of accumulation in food vacuole | -parasites that have this mutation but can't replicate as quickly
45
Chloroquine facts
treats erythrocytic forms of sensitive strains - well absorbed - formulated for oral use - very large volume distribution (slowly released from tissue) - initial half life of 3-5 days, terminal half-life 1-2 months
46
Chloroquine: time-dependent killing
- acts slower than artemisinin - more effective if drug concentration was above the minimal drug concentration - can maintain for a long period of time at high concentrations in blood
47
chloroquine resistance malaria
P. falciparum, mutations in PfCRT1 - localized to food vacuole - causes reduced accumulation of chloroquine - over-expression of PfMDR1
48
adverse effects of chloroquine
- usually very well tolerated - Pruritus - contrainicated for: psoriasis, porphyria - retina or visual field abnormalities - myopathy
49
chloroquine like drugs
``` mefloquine lumefantrine peperaquine amodiaquine halofantrine tafenoquine ```
50
Quinine
-bark from cinchona tree (tonic water has quinine in it)
51
Quinine and Quinidine
- act on blood schizonticide - active against all plasmodium and babeoisis - MOA prbably similar to chloroquine - IV for severe falciparum, oral for uncomplicated - metabolism CYP3A4 (can raise warfarin and digoxin) interactions with anti-retroviral drugs
52
quinine adverse effects?
Cinchonism: tinnitis, headache, N, dizziness, flushing and visual disturbances -cardiotoxicity -can stimulate uterine contractions -hemolysis (G6PD deficiency, black water fever) severe hypotension can occur from too rapid infuson
53
Mefloquine
- evidence of increasing resistance - used for treatment and pro - erythrocytic forms-falciparum and vivax
54
mefloquine adverse effects
generic name: Lariam | neuropsychiatric toxicity: seizures, toxic psychosis, sleep disturbance
55
Primaquine
- MOA unknown - drug of choice for liver stages P. vivax and ovale - gametocidal against all 4 - well absorbed - some resistance - only drug active against hyponozoites
56
Primaquine adverse effects
too toxic for long term drug use | -contraindications: G6PD deficiency (predisposes for hemolytic anemia), pregnancy
57
patients to avoid giving Primaquine too?
-avoid in patients with: granulocytopenia, or methemoglobinemia, receiving potentially myelosuppressive drugs, disorders that commonly include myelosuppresion
58
what does sulfadoxine target?
DHPS
59
Fansidar (pyrimethamine-sulfadoxine)
folate synthesis inhibitors - slow acting erythrocyte schizonticides - toxoplasmosis - pyrimethamine- inhibits plasmodia DHF
60
antifolates
toxoplasmosis | pnueomocystis (fungal)
61
use of antifolates
single use not recommended | -
62
Malarone
treatment and chemoprop - combination fo proguanil and atavaquone - taken with food - atavaquone is alternative therapy for P. jiroveci
63
Atavaquone MOA
disrupts mito electron transport
64
antibiotics as anti-malaria drugs
tetracycline, doxycycline (paired with quinine usually), clindamycin - target components of apicoplast: plant like organelle that carries out many biochemical processes - antibiotics target this organelle
65
Non-malaria antiprotozoal drugs
drugs for GI lumen or tissue infections
66
associated diseases for Non-malaria antiprotozoal drugs
``` amebiasis cryptosporidiosis giardiasis leishmaniasis pneumocystis pneumonia toxoplasmosis trichomoniasis trypansomiasis ```
67
P. vivax or P. ovale CQ sensitive drugs:
CQ sensitive: Chloroquine, hydroxycholorquine + primaquine
68
P. vivax or P. ovale CQ resistant drugs:
quinine sulfate + doxycycline, or tetracycline + primaquine atovaquone + proguanil + primaquine Mefloquine+ primaquine
69
P. malariae or P knowlesi drugs
chloroquine or hydrozychloroquine sulfate
70
fansidar blocks what proteins?
PABA-> dihydrofolic by dihyrdropteroate synthase (DHPS) dihydrofolic acid-> tetrahydrofolic acid by dihrydofolate reductase (DHFR) no purines
71
pyrimethamine sulfadoxine other name is
fansidar
72
what does fansidar do?
folate synthesis inhibitors - slow acting erythrocytic schizonticides - toxoplasmosis
73
first line therapy for pneumocystis
trimethoprim + sulfamethoxazole | atavaquone alternative
74
why is use of sing antifolate not recommended?
resistance develops quickly - paired with other drugs - both have long half lives
75
half life of pyrimethamine
90 hours
76
half life of sulfadoxine
170 hours
77
drug of choice for extraintestinal entamoeba histolytica, giardiasis, trichomoniasis
metronidazole | -kills trophozites but NOT CYSTS
78
what usually follows treatment of metrondiazole
luminal drug to eliminate asymptomatic infection
79
MOA of metrondiazole
not known but | anaerobes have electron transport proteins with low redox potential-> active metrondiazole may target DNA parasite
80
similar drug to metrondiazole
tinidazole | less toxic

Pharmacology (14 decks)

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