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Antiparasitic drugs Flashcards

1
Q

Antiparasitic drugs

Groups of drugs that treat malaria

A
  • Heme polymerization drugs (quinolones)
  • Tissue schizonticide drugs
  • Artemisin derivatives
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2
Q

Antiparasitic drugs

Chloroquine and Quinidine/quinine are _________ drugs

A

Quinolones (Heme polymerization)

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3
Q

Antiparasitic drugs

Chloroquine admin. and absorption

A
  • Well absorbed from the gastrointestinal (GI) tract.
  • Rapidly absorbed from intramuscular (IM) and subcutaneous (SC) sites.
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4
Q

Antiparasitic drugs

How does cloroquine work against plasmodium?

A
  • Inhibits heme polymerization, preventing detoxification of toxic heme, leading to parasite death.
  • Accumulates in the parasite’s digestive vacuole.
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5
Q

Antiparasitic drugs

What is chloroquine used for?

A
  • Malaria treatment & prophylaxis (P. vivax, P. ovale, P. malariae, P. knowlesi).
  • Autoimmune diseases (RA, lupus – hydroxychloroquine preferred).
  • Hepatic amebiasis
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6
Q

Antiparasitic drugs

First line agent for P. ovale and P. malariae

A

Chloroquine

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7
Q

Antiparasitic drugs

Since it has no activity on liver-stage parasites, Chloroquine requires _____ to prevent relapses in P. vivax and P. ovale stages

A

Primaquine

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8
Q

Antiparasitic drugs

Chloroquine is ineffective against…

A

Chloroquine-resistant P. falciparum

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9
Q

Antiparasitic drugs

If there is no response to chloroquine, the alternative treatment of choice would be

A

Quinine + tetracycline/doxycycline

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10
Q

Chloroquine

Cardiovascular toxicity

A
  • Hypotension
  • Vasodilation
  • Suppressed myocardial function
  • Cardiac arrhytmias
  • Cardiac arrest!!
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11
Q

Chloroquine

Neurological toxicity

A

Confusion, convulsions, coma

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12
Q

Chloroquine

Cardiac adverse effects

A
  • Widening of QRS
  • T wave abnormalities
  • Cardiomyopathy
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13
Q

Antiparasitic drugs

T/F: Retinopathy and ototoxicity may occur under chloroquine use

A

True

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14
Q

Chloroquine

Hematological and skin/mucosa adverse effects

A
  • Hemolysis in G6PD-deficient patients
  • Lichenoid skin eruptions
  • Bleaching of hair and nail/mucous membranes discoloration
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15
Q

Chloroquine

Absolute contraindications

A
  • Epilepsy
  • Myasthenia gravis
  • Psoriasis
  • GI, neurological, liver or hematological disorders
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16
Q

Chloroquine

Safe in pregnancy?

A

Safe in pregnancy

Caution is advised

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17
Q

Chloroquine

How do plasmodium species develop resistance to chloroquine?

A
  • Mutations in pfcrt (chloroquine resistance transporter) reduce drug accumulation.
  • P. vivax resistance linked to pvcrt overexpression.
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18
Q

Antiparasitic drugs

Quinidine/quinine are drugs used for ________ tx. and they target ___________

A
  • Malaria treatment
  • Heme polymerization
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19
Q

Antiparasitic drugs

Quinine/quinidine

A
  • Readily absorbed when given orally or intramuscularly (IM).
  • Oral absorption >80%, even in patients with diarrhea.
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20
Q

Antiparasitic drugs

Standard of care for severe malaria

A

IV quinine ONLY until artemisin therapy can begin

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21
Q

Antiparasitic drugs

Slower acting blood schintozides such as (–) and (–) are given with quinines to enhance their efficacy

Especially for multi-drug resistant P. falciparum

A

Tetracyclins or clindamycin

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22
Q

Quinine/quinidine

MOA against plasmodium

A
  • Blood schizonticide, disrupts parasite metabolism.
  • Used in combination therapy to prevent resistance.
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23
Q

Quinine/quinidine

Major side effects

A
  • Cinchonism (tinnitus, headache, visual disturbances, nausea).
  • Hypoglycemia, hypotension, cardiac arrhythmias.
  • Severe hemolysis (Blackwater fever in G6PD deficiency).
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24
Q

Antiparasitic drugs

In malaria tx. quinines should be avoided in

A
  • Patients with tinnitus or optic neuritis.
  • Patients with cardiac dysrhythmias (requires same precautions as quinidine).
  • Pregnancy (risk of hypoglycemia)
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25
Q

Drug interactions

Quinine + antacids (aluminum containing)

A

Delayed absorption

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26
Q

Drug interactions

Warfarin, anticoagulants, glycosides, neuromuscular blockers + quinine/quinidine

A

Quinine/quinidine increases plasma levels of those drugs

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27
Q

Antimalaria drugs

Urine acidification/rifampin + quinine/quinidine

A

Faster elimination of quinine

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28
Q

Resistance

Quinine/quinidine vs. chloroquine

A

There are more chloroquine-resistant strains

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29
Q

Antimalarial drugs

Primaquine is a

A

Tissue schizonticide

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30
Q

Antimalarial drugs

Primaquine’s absorption

A

Nearly 100% from GI tract

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31
Q

Antimalarial drugs

Acts against primary and latent hepatic stages of Plasmodium spp.

Tissue schizonticide

A

Primaquine

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32
Q

Antimalarial drugs

Primaquine prevents relapses in

A

P. vivax and P. ovale

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33
Q

Antimalarial drugs

Why is primaquine unsuitable in acute episodes of malaria?

A

Inactive against asexual blood-stage parasites

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34
Q

Antimalarial drugs

Primaquine therapeutic uses

A
  • Prevents malaria relapses (terminal prophylaxis).
  • Destroys gametocytes, blocking transmission
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35
Q

Antimalarial drugs

Primaquine should be administered with a blood schizonticide like (–) or (–) to…

A
  1. Quinine
  2. Chloroquine
  • Erradicate erythrocitic stages of the parasite
  • Reduce drug resistance risk
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36
Q

Antimalarial drugs

Primaquine’s major toxicities

A

Mild anemia, metahemoglobinemia (cyanosis), leukocytosis, hemolysis and hemolytic anemia in G6PD-deficient individuals

Other: hypertension, arrhytmias, CNS symptoms

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37
Q

Antimalarial drugs

When using primaquine, chloroquine and dapsone may enhance _______ risk

A

Metahemoglobinemia

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38
Q

Antimalarial drugs

Primaquine contraindications

A
  • G6PD deficiency
  • Pregnancy
  • Acutely ill patients with systemic diseases (active RA, lupus) causing granulocytopenia

Patients should watch out for dark/blood urine - hemolysis

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39
Q

Antimalarial drugs

Primaquine MOA

A
  • Acts on liver hypnozoites (P. vivax, P. ovale).
  • Gametocytocidal against P. falciparum.
  • Disrupts mitochondrial electron transport, leading to oxidative stress and parasite death.
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40
Q

Antimalarial drugs

Primaquine resistance

A
  • Alterations in mitochondrial electron transport proteins = < drug effectiveness
  • Increased antioxidant defenses that counteract oxidative stress
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41
Q

Antimalarial drugs

Food + primaquine

A

Best taken with food to reduce GI irritation

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42
Q

Primaquine

CYP3A4 inhibitors (ketoconazole, erythromycin)

A

Increase drug levels

43
Q

Antimalarial drugs

Rifampin + primaquine

A

Reduced efficacy

44
Q

Antimalarial drugs

QT-prolonging drugs

Chloroquine, Moxifloxacin

A

Enhanced cardiotoxic effects

45
Q

Antimalarial drugs

Artemisin derivatives

46
Q

Artemisin

Derivatives and administration

A
  • dihydroartemisinin (PO)
  • artemether (PO, IM, IV)
  • artesunate (IV, IM, Rectal)
47
Q

Antimalarials

Optimized tx. for P. falciparum malaria and P. vivax

A

Artemisins (specifically parenteral artesunate)

48
Q

Antimalarials

Unless it is parenteral artesunate, the rule of artemisins is

A

THEY ARE NOT USED AS MONOTHERAPY

Combine with slower-eliminated partner drugs with different MOA = 1st LT

49
Q

Antimalarial drugs

Artemisin MOA

A
  • Activated by heme in parasite food vacuole, producing free radicals and protein alkylation

Disrupts parasite proteins & membranes (by alkylation and oxidation), leading to rapid parasite death.

50
Q

Antimalarials

Highly potent against asexual blood-stage parasites.

51
Q

Antimalarial drugs

Artemisin common side effects

A
  • Reticulocyte and neutrophil count decrease
  • Increased transaminase levels = mild liver stress
  • Allergic reactions
52
Q

Artemisin

Plasmodium resistance mechanisms

A

Mutations in K13-propeller protein (kelch13 gene) linked to delayed clearance.

Altered parasite stress response reduces drug susceptibility.

Combination therapy (ACTs) is used to prevent resistance.

53
Q

Antimalarials

Food/drugs + artemisin

A
  • Food = improved torelability
  • rifampin, phenytoin, carbamazepine = reduce efficacy
  • Ketoconazole, clarithromycin = increase toxicity risk
54
Q

Artemisin

QT prolonging drugs like quinolones and antipsychotics should be

55
Q

Antiparasitic drugs

Drug groups that treat amebiasis

A

*DNA synthesis inhibitor

56
Q

Antiparasitic drugs

Metronidazole is a

A

DNA synthesis inhibitor

Used to treat amebiasis

57
Q

Metronidazole

Admin. form

A

Oral
IV
Intravaginal
Topical

58
Q

Metronidazole

Has activity against

A

Anaerobic microorganisms (protozoas and bacteria (+/-/spore/microaerophillic)

59
Q

Antioarasitic drugs

Metronidazole therapeutic uses

A
  • Trichomoniasis (T. vaginalis)
  • Amebiasis (Entamoeba histilytica)
  • Giardiasis
  • Prophylaxis in C. difficile infections before colorrectal surgery
60
Q

Antiparasitics

First line of treatment for giardiasis and agent of choice ot symptomatic amebiasis

A

Metronidazole

61
Q

Metronidazole

MOA

A
  • Prodrug gets reductive activation of the nitro group
  • Electro-transfer to drugs forms free radicals
  • Interaction of free radicals w/DNA leads to strand breaks and lethal damage
  • Cycle of regeneration leads to continous activation of the drug

Amebiasis

62
Q

Metronidazole

Common side effects

A
  • Headache, nause
  • Dry mouth
  • Metallic taste
  • GI distress
  • NEUROTOXICITY
  • Steven-Johnson
63
Q

Antiparasitics

Neurotoxicity by metronidazole use can be seen as

A

Encephalopathy and convulsions

64
Q

Antiparasitic drugs

Metronidazole is refused by ____ and should be withdrawn if ____, paretesthesias or urticaria/sensitivity are present

A
  • Pediatric patients
  • Numbness
65
Q

Patients that shouldn’t take metronidazole

A
  • 1st trimester of pregnancy
  • Severe hepatic disease
  • CNS disease
66
Q

Antiparasitic drugs

T/F: metronidazole and disulfiramic-like drugs or warfarins can be taken together

67
Q

Antiparasitic drugs

Aerobic microorganisms are resistant to metronidazole because…

A
  • Reduced activation of the prodrug by decreased ferredoxin levels.
  • Upregulation of antioxidant defenses neutralizing toxic free radicals.
  • Efflux pumps reducing intracellular drug concentration.
68
Q

Antiparasitic drugs

Disulfiram-like reaction with alcohol happens with

A

Metronidazole

69
Q

Antiparasitics

Quinfamide is an:

70
Q

Antiparasitic drugs

Drug used to treat ONLY the luminal form of amebiasis (asymptomatic carriers of Entamoeba histolytica)

Non effective for extraintestinal amebiasis

A

Quinfamide

71
Q

Antiparasitic drugs

Quinfamide’s action

A
  • Acts locally in the intestinal lumen
  • Disrupts the membrane integrity of Entamoeba histolytica and leads to parasite death

Exact molecular mechanism is not known

72
Q

Amebicides

Quinfamide’s adverse effects

A
  • Mild GI symptoms
  • Headache, dizziness, skin and rash
73
Q

Amebicides

Quinfamide should not be used in cases of:

A
  • Severe liver disease
  • Pregnancy
  • Systemic amebiasis
74
Q

Antiparasitics

Broad spectrum activity against protozoa drug

A

Pentamidine

75
Q

Amebiasis

Pentamidine ADME

A

IV
Aerosol
Doesn’t cross BBB

76
Q

Amebiasis

Pentamidine has activity against ______ and _______ some fungi, and it is the tx. early stage T. brucei gambiense

A

Protozoa and fungi

77
Q

Antiparasitics

First line of treatment for children under 6 years or 20 kg in cases of amebiasis

A

Quinfamide

78
Q

Antiparasitics

Alternative treatment of cutaneous leishmainiasis and prophylaxis of P. jirovecii pneumonia

A

Quinfamide

79
Q

Antiparasitic drugs

Pentamidine’s MOA

A

Unknown mechanism

80
Q

Antiparasitic

Hypotension + tachychardia
Pancreatitis and hyperglucemia (insulin-dependent diabetes)
Renal toxicity
Side effects of…

A

Pentamidine

Amebiasis

81
Q

Antiparasitics

Pentamidine MOA

A
  • Uptake by high affinity transportet TbAQP2
  • Affection of mitochondrial function and DNA integrity

Molecular mechanism not fully understood

82
Q

Antiparasitics

Pentamidine contraindications

A
  • Hypersensitivity
  • Renal failure or disfunction
  • Cardiovascular conditions (arrhytmia or heart disease)
  • TERATOGENIC EFFECTS

Contraindicated in pregnancy during the firs trimester

83
Q

Antiparasitic drugs

Pentamidine

A
  • Decreased drug uptake due to mutations in transport proteins.
  • Efflux pump activation, reducing intracellular drug concentration.
  • Altered mitochondrial metabolism, decreasing drug-induced toxicity.
  • Overexpression of detoxification enzymes, neutralizing pentamidine’s effects.
84
Q

Helmintic infections

Microtubule inhibitors include

A
  • Albendazole
  • Mebendazole
85
Q

Microtubule inhibitors

Albendazole ADME

A
  • Oral
  • Absorption enhanced by the presence of fatty food
  • Given to children over 2 years of age
86
Q

Antiparasitics

What GI nematodes does albendazole treat?

A
  • Ascaris lumbricoides (roundworm)
  • Trichuris trichiura (whipworm)
  • Enterobius vermicularis (pinworm)
87
Q

Antiparasitics

How does albendazole help in hydatid cyst infections?

A

Preoperative use reduces the risk of cyst rupture

88
Q

What parasites does albendazole prevent from producing eggs?

A

Echinococcus
Taenia solium

89
Q

Antiparasitics

Preferred treatment for T. solium larval infection in the brain

Neurocysticercosis

A

Albendazole

90
Q

Antiparasitics

Because of its broad-spectrum, safety, and efficacy this is a key drug in parasitic disease control programs

A

Albendazole

91
Q

Albendazole

MOA

Antiparasitics

A
  • Binds to B-tubulin preventing microtubule polymerization
  • This leads to glucose uptake which then starves the parasite
  • Causes the disruption of cell division and motility
  • Worm death
92
Q

Antiparasitics

In echinococcus and T. solium, albendazole disrupts ________ and prevents ________

Albendazole sulfoxide inhibits fumarate reductase

A
  • Reproductive structures
  • Egg reproduction
93
Q

Antiparasitics

Albendazole crosses the intestinal wall, this makes it effective for:

A

Helmintic infections

94
Q

Antiparasitics

Albendazole adverse effects

A
  • Hepatotoxicity
  • Long term = bone marrow toxicity
95
Q

Antiparasitics

This microtubule inhibitor has poor absorption and rapid first-pass metabolism at intestinal wall and liver

Anti-helmintic

A

Mebendazole

96
Q

Antiparasitics

Mebendazole is a first line treatment for common GI nematode infections incluiding:

A
  • Pinworm
  • Round
  • Whipworm
  • Hookworm
97
Q

Antiparasitics

T/F: mebendazole is easier to use in pediatric populations

98
Q

Antiparasitics

Mebendazole MOA

A
  • Selective binding to β-tubulin.
  • Inhibits microtubule polymerization, reducing glucose uptake and disrupting cell division.
  • Inhibits mitotic spindle formulation and affects secretory granule transport –> toxic metabolites
99
Q

Mebendazole adverse effects

A
  • Gastrointestinal issues (abdominal pain, diarrhea).
  • Rare: Bone marrow suppression.
100
Q

Antiparasitics

Why is mebendazole avoided in <1 year olds?

A

Risk of convulsion

101
Q

Mebendazole contraindications

A
  • Grapefruit juice
  • AVOID IN PREGNANCY (CAT. C)
  • Anaphylaxis to other benzimidazoles
  • Not recommended in liver disease patients
102
Q

Anti-helmintics

Resistance to microtubule inhibitors is given by

A
  • Due to genetic mutations in the B-tubulin gene that reduce drug binding and decreased efficacy
  • Drug efflux mechanisms because of P-glycoprotein overexpression
103
Q

Anti helmintics

What is the most common mutation associated with resistance to mebendazole?

104
Q

Anti helmintics

Cimitidine + Mebendazole

A

Mebendazole increases plasma levels and time of action

Antimicrobial's pharmacology (7 decks)

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