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Pharmacology 4090 > Anti- Parasitic Drugs > Flashcards

Anti- Parasitic Drugs Flashcards

1
Q

Macroscopic parasites

A

taenia species (tapeworms), enterobius (pinworm), pediculus (head louse)

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2
Q

Microscopic parasites

A

Entamoeba (amebiasis), giardia (beaver fever), trichomonas, plasmodium (malaria)

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3
Q

Beef tapeworm

A

Taenia saginata

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4
Q

Pork tapeworm

A

Taenia solium

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5
Q

Life cycle of Taenia species

A

Humans ingest undercooked meat → attaches to intestine → becomes adult → eggs get into feces → cattle or pigs ingest contaminated vegetation → oncospheres get into musculature and stay there

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6
Q

Structures at anterior end of tapeworm

A

Hooks and suckers

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7
Q

Cestocidal drugs

A

Praziquantel, niclosamide

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8
Q

Praziquantel mechanism

A

Binds outer layer of parasite and produces vacuoles, which causes an influx of calcium and muscle contraction → paralysis, dislodgement, death

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9
Q

Pk of praziquantel

A

High bioavailability orally

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10
Q

Clinical uses of praziquantel

A

Drug of choice against cestode infections, given in a single oral dose but cannot chew due to bitter taste

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11
Q

Adverse reactions to praziquantel

A

Mild nausea, headache, abdominal discomfort

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12
Q

Niclosamide mechanism

A

Inhibits ATP production and rapidly kills scolex and segments of adult tapeworms

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13
Q

Pk of niclosamide

A

Minimally absorbed from gi tract (good thing)

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14
Q

Clinical uses of niclosamide

A

Second choice for taenia species, given as a single oral done but is cheaper and accessible

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15
Q

Adverse reactions of niclosamide

A

Rare; nausea, vomiting, diarrhea

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16
Q

Prevention of tapeworm reinfection

A

Fully cook meat

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17
Q

Life cycle of enterobius vermicularis

A

Humans ingest eggs → larvae in si → adults in caecum → migrate to perianal region at night to lay eggs → eggs mature in 4-6 hours → ingested again

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18
Q

Clinical presentation of enterobius vermicularis

A

School-aged, asymptomatic, itching causes irritability, incontinence, weight loss

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19
Q

Minimizing enterobius infection

A

Personal hygiene, clean bedrooms, bed linen and night clothes changed frequently

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20
Q

Drugs for enterobius vermicularis

A

Mebendazole, pyrantel

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21
Q

Mebendazole pk

A

Given orally and minimally absorbed

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22
Q

Mebendazole mechanism

A

Binds beta tubulin so microtubules can’t polymerize → inhibits motility, glucose uptake, and division so parasite is slowly killed and expelled in feces

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23
Q

When you should not give mebendazole

A

When pt has diarrhea because quicker transit time means lower efficacy

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24
Q

Clinical uses of mebendazole

A

Pinworms - treat twice @2week intervals

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25
Q

Adverse reactions of mebendazole

A

Short-term is basically free of adverse effects, but is teratogenic

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26
Q

Pyrantel pk

A

Poorly absorbed from gi tract

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27
Q

Pyrantel mechanism

A

Acts at neuromuscular junction on nicotinic receptors to cause release of ACh and inhibition of AChE → paralysis → expulsion

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28
Q

Pyrantel clinical uses

A

Pinworms but narrower spectrum, treat twice @ 2 week interval

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29
Q

Adverse reactions of pyrantel

A

Mild nausea, vomiting, diarrhea

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30
Q

Life cycle of pediculus capitis

A

Stay on head and feed on human blood; go from egg to 1st nymph in 8-9 days and egg to adult in 18-21 days

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31
Q

Clinical presentation of pediculus capitis

A

Itchy head, most easily seen behind ears or back of neck

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32
Q

Transmission of pediculus capitis

A

Mainly direct head-to-head contact

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33
Q

Drugs for pediculus capitis

A

Permethrin and malathion

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34
Q

Permethrin mechanism

A

Keeps voltage-gated sodium channels open, which causes depolarization and paralysis

35
Q

Pk of permethrin

A

Minimally absorbed through skin, rapidly inactivated in liver, high prevalence of resistance

36
Q

Malathion mechanism

A

Irreversibly inhibits AChE —>paralysis

37
Q

Adverse reactions of permethrin and malathion

A

Itching or burning of scalp that can persist for days after lice are killed

38
Q

Principles of pediculus capitis treatment

A

They don’t kill eggs, retreat at 9-10 day intervals, treat bedmates at same time, treat household, manually remove nits after treatment

39
Q

Protozoa

A

Eukaryotes with similar metabolic processes to the host, antiprotozoal drugs may cause significant toxicity

40
Q

Entamoeba histolytica

A

Parasite that causes amebiasis

41
Q

Amebiasis

A

Disease caused by E. Histolytica

42
Q

Life cycle of E histolytica

A

Ingested by humans → cysts released in si and become trophozoites → turn back into cysts after replication → excreted in feces

43
Q

Outcomes of amebiasis

A

Asymptomatic colonization in colon, invasive amoebic colitis, liver abscess, ameboma

44
Q

Categories of amebicidal drugs

A

Luminal amebicides, systemic amebicides, mixed amebicides

45
Q

Luminal amebicides

A

Used if you only have cysts and trophozoites it the bowel lumen (asymptomatic)

46
Q

Systemic amebicides

A

Used if you have parasites in the intestinal wall and liver, but do not killed trophozoites or cysts in lumen

47
Q

Mixed amebicides

A

Drug of preference for sick pts; kill parasites in lumen, wall, and liver

48
Q

Metronidazole pharmacokinetics

A

Given orally, readily absorbed, and extensively distributed; metabolized by mixed-function oxidase and glucuronylation in liver, all excreted in urine; clearance will decrease if impaired liver function

49
Q

Metronidazole mechanism

A

Ferrodoxin-like, low-redox potential, electron transport proteins transfer electrons to nitro groups of metronidazole → cytotoxic products

50
Q

Metronidazole adverse effects

A

Nausea, vomiting, headache, abdominal cramps, metallic taste, alcohol causes nausea and vomiting, avoided in pregnant/nursing women because mutagenic in bacteria

51
Q

Clinical uses of metronidazole

A

Drug of choice for diarrhea/dysentery but not reliable for luminal parasites so have to be given with luminal amebicide

52
Q

Iodoquinol uses

A

After treatment of symptomatic amebiasis and for asymptomatic infections; effective against luminal stages

53
Q

Iodoquinol adverse effects

A

Rash, diarrhea, peripheral neuropathy, optic neuritis (avoid long-term use)

54
Q

Treatment protocol for metastatic amebiasis

A

High dosage metronidazole followed by iodoquinol

55
Q

Life cycle of Giardia lamblia

A

Ingested through contaminated food /water → get into intestine but do not invade → excreted in feces but only cysts survive in environment

56
Q

Clinical signs of Giardia

A

Usually asymptomatic but can cause severe diarrhea

57
Q

Drug of choice for Giardia

A

Metronidazole at low doses but do not treat asymptomatic infections

58
Q

Trichomonas vaginalis residence

A

Female lower genital tract, male urethra and prostate; do not survive in external environment, do not have cyst form

59
Q

Trichomoniasis

A

Common sexually transmitted disease

60
Q

Clinical signs of trichomoniasis

A

Vaginal discharge, vulvar itching, urination discomfort, men usually asymptomatic but can have urethral discharge or burning sensation

61
Q

Trichomoniasis treatment

A

Metronidazole, typically single dose unless resistant, systemic therapy preferred, always treat sexual partner

62
Q

Most severe form of malaria

A

Plasmodium falciparum

63
Q

Only parasites of malaria that cause clinical illness

A

Erythrocytic

64
Q

Clinical signs of malaria

A

Headache, back and limb pain, anorexia, nausea, fever, chills, anemia

65
Q

Cerebral malaria

A

Slowly lapse into coma with convulsions because parasitized RBCs block cerebral blood vessels

66
Q

Plasmodium life cycle

A

Infected mosquito injects sporozoites into human → infect liver and multiply asexually as tissue schizonts → liver cells burst and release merozoites that infect red blood cells → merozoites reproduce asexually in red blood cells as blood schizonts → infected RBCs burst and release gametes → mosquito picks up gametes and produces sporozoites

67
Q

Categories of malaria drugs

A

Tissue schizonticides, blood schizonticides, gametocides

68
Q

Treatment of falciparum and malariae

A

Only need blood schizonticides

69
Q

Treatment of vivax and ovale

A

Need tissue and blood schizonticides

70
Q

Prevention of mosquito bites

A

Insect repellents, insecticides, appropriate clothing, bed nets with permethrin

71
Q

Chloroquine clinical uses

A

Chemo prophylaxis if parasites are sensitive to it, treatment of chloroquine-sensitive falciparum

72
Q

Chloroquine pk

A

Taken orally once/week, rapidly absorbed and distributed, is a blood schizonticide, metabolized by liver and excreted in urine

73
Q

Chloroquine mechanism

A

Concentrates in food vacuole and prevents polymerization of heme into hemozoin, resulting in oxidative damage and lysis

74
Q

Chloroquine resistance

A

Mutations in membrane transporter

75
Q

Chloroquine adverse effects

A

Minimal at low doses, at high doses can get nausea, vomiting, blurred vision, but can take after meals to minimize

76
Q

Mefloquine clinical uses

A

Chemoprophylaxis and treatment of chloroquine-resistant falciparum

77
Q

Mefloquine resistance

A

Less common; associated with quinine and halofantrine resistance

78
Q

Mefloquine pk

A

Given orally once/week, well absorbed and distributed, eliminated slowly, blood schizonticide

79
Q

Mefloquine mechanism

A

Concentrated in parasite and may inhibit heme polymerization; final result is membrane damage

80
Q

Mefloquine adverse reactions

A

Neuropsychiatric toxicity, nausea, vomiting, dizziness, sleep and behaviour disturbances

81
Q

Doxycycline clinical lenses

A

Chemo prophylaxis of multidrug resistant falciparum, treatment of falciparum with quinidine or quinine

82
Q

Doxycycline pk

A

Given daily orally, blood schizonticide

83
Q

Doxycycline mechanism

A

Inhibits protein synthesis

84
Q

Doxycycline adverse effects

A

Infrequent gi symptoms, photosensitivity

Pharmacology 4090 (11 decks)

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