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Pharmacology > Antiparasitics: Antihelminthic Drugs > Flashcards

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
Q

Primaquine

A

primarly P. vivax in area

-start 1-2 days prior and 7 days after

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26
Q

Doxycycline

A

start 1-2 days prior and continue 4 weeks after

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27
Q

Treatment options for malaria

A
  • depends on the type (species)
  • where they were when they got infected (for drug resistance)
  • Clinical status of patient (other conditions, accompanying illnesses, pregnant)
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28
Q

Drugs for uncomplicated malaria? Chloroquine sensitive

A

Chloroquine and hydroxychloroquine

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29
Q

Drugs for uncomplicated malaria? chloroquine resistant

A 
atovaquone+ Proguanil
Artmether + lumefantrine
Quinine sulfate
Doxycycline, tetracycline, clindamycin
melfoquine
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30
Q

drugs for severe complicated malaria?

A

Quinidine gluconate- IV

  • plus doxycycline or tetracycline
  • consult a cardiologist and experienced physician monitor
  • can have severe cardiac complications-if so stop drug
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31
Q

Artesunate

A

alternative if quinidine gluconate not available or not tolerated
-IV only
Has IND

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32
Q

Artemisinin

A

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
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33
Q

advantages of artemisinin

A
  • 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
Q

what species is artemisinin used for?

A

Chloroquine resistant P. falciparium

35
Q

disadvantage of artemisinin?

A

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
Q

artemisinin combination therapy?

A

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
Q

artemisinin combination drugs

A

artemether+ lumefantrine
artensunate+ mefloquine
dihydroartemisinin+ piperaquine

38
Q

artemisinin anti-malarial effect associated with Cmax?

A

concentration dependent killing

39
Q

artemisinin derivatives

A

Artesunate: water soluble

Artemether:lipid soluble

40
Q

adverse side effects of aretmisinin?

A

N&V, diarrhea, and dizziness

Not recommended for 1st trimester for uncomplicated malaria

41
Q

quinolines

A

2 classes:

  1. ) chemical substituent at 4 position
  2. ) chemical substituent at 8th position
42
Q

quinolines derivatives function

A

blocking polymerization of heme, accumulates in food vacuoles (pigment vacuole) and inhibits heme polymerization

43
Q

hemoglobin metabolism in parasites

A

-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
Q

resistance of quiolines?

A

associated with lack of accumulation in food vacuole

-parasites that have this mutation but can’t replicate as quickly

45
Q

Chloroquine facts

A

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
Q

Chloroquine: time-dependent killing

A
  • 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
Q

chloroquine resistance malaria

A

P. falciparum, mutations in PfCRT1

  • localized to food vacuole
  • causes reduced accumulation of chloroquine
  • over-expression of PfMDR1
48
Q

adverse effects of chloroquine

A
  • usually very well tolerated
  • Pruritus
  • contrainicated for: psoriasis, porphyria
  • retina or visual field abnormalities
  • myopathy
49
Q

chloroquine like drugs

A 
mefloquine
lumefantrine
peperaquine
amodiaquine
halofantrine
tafenoquine
50
Q

Quinine

A

-bark from cinchona tree (tonic water has quinine in it)

51
Q

Quinine and Quinidine

A
  • 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
Q

quinine adverse effects?

A

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
Q

Mefloquine

A
  • evidence of increasing resistance
  • used for treatment and pro
  • erythrocytic forms-falciparum and vivax
54
Q

mefloquine adverse effects

A

generic name: Lariam

neuropsychiatric toxicity: seizures, toxic psychosis, sleep disturbance

55
Q

Primaquine

A
  • 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
Q

Primaquine adverse effects

A

too toxic for long term drug use

-contraindications: G6PD deficiency (predisposes for hemolytic anemia), pregnancy

57
Q

patients to avoid giving Primaquine too?

A

-avoid in patients with: granulocytopenia, or methemoglobinemia, receiving potentially myelosuppressive drugs, disorders that commonly include myelosuppresion

58
Q

what does sulfadoxine target?

A

DHPS

59
Q

Fansidar (pyrimethamine-sulfadoxine)

A

folate synthesis inhibitors

  • slow acting erythrocyte schizonticides
  • toxoplasmosis
  • pyrimethamine- inhibits plasmodia DHF
60
Q

antifolates

A

toxoplasmosis

pnueomocystis (fungal)

61
Q

use of antifolates

A

single use not recommended

-

62
Q

Malarone

A

treatment and chemoprop

  • combination fo proguanil and atavaquone
  • taken with food
  • atavaquone is alternative therapy for P. jiroveci
63
Q

Atavaquone MOA

A

disrupts mito electron transport

64
Q

antibiotics as anti-malaria drugs

A

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
Q

Non-malaria antiprotozoal drugs

A

drugs for GI lumen or tissue infections

66
Q

associated diseases for Non-malaria antiprotozoal drugs

A 
amebiasis
cryptosporidiosis
giardiasis
leishmaniasis
pneumocystis pneumonia
toxoplasmosis
trichomoniasis
trypansomiasis
67
Q

P. vivax or P. ovale CQ sensitive drugs:

A

CQ sensitive: Chloroquine, hydroxycholorquine + primaquine

68
Q

P. vivax or P. ovale CQ resistant drugs:

A

quinine sulfate + doxycycline, or tetracycline + primaquine

atovaquone + proguanil + primaquine

Mefloquine+ primaquine

69
Q

P. malariae or P knowlesi drugs

A

chloroquine or hydrozychloroquine sulfate

70
Q

fansidar blocks what proteins?

A

PABA-> dihydrofolic by dihyrdropteroate synthase (DHPS)

dihydrofolic acid-> tetrahydrofolic acid by dihrydofolate reductase (DHFR)

no purines

71
Q

pyrimethamine sulfadoxine other name is

A

fansidar

72
Q

what does fansidar do?

A

folate synthesis inhibitors

  • slow acting erythrocytic schizonticides
  • toxoplasmosis
73
Q

first line therapy for pneumocystis

A

trimethoprim + sulfamethoxazole

atavaquone alternative

74
Q

why is use of sing antifolate not recommended?

A

resistance develops quickly

  • paired with other drugs
  • both have long half lives
75
Q

half life of pyrimethamine

A

90 hours

76
Q

half life of sulfadoxine

A

170 hours

77
Q

drug of choice for extraintestinal entamoeba histolytica, giardiasis, trichomoniasis

A

metronidazole

-kills trophozites but NOT CYSTS

78
Q

what usually follows treatment of metrondiazole

A

luminal drug to eliminate asymptomatic infection

79
Q

MOA of metrondiazole

A

not known but

anaerobes have electron transport proteins with low redox potential-> active metrondiazole may target DNA parasite

80
Q

similar drug to metrondiazole

A

tinidazole

less toxic

Pharmacology (14 decks)

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