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Pharmacology > Antimalarials > Flashcards

Antimalarials Flashcards

1
Q

P. falciparum and P. malariae life cycle.:

  1. How many cycles of liver cell invasion?
  2. Parasites in what stage have to be eliminated?
A
  1. Only have one cycle of liver cell invasion

- liver infection ceases in

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2
Q

P. vivax and P. ovale life cycle.:

Parasites in what stages have to be eliminated?

A

hepatic and erythrocytic stages have to be eliminated!

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3
Q

Incubation periods of malarial pathogens:

A

P. vivax 2 –> 17 days
P. falciparum 9 –> 14 days
P. ovale 16 –> 18 days
P. malariae 18 –> 40 days (can be years)

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4
Q

Treatment of malariae must be guided by 3 main factors?

A
  1. Infecting Plasmodium species
  2. Clinical status of patients
  3. Drug susceptibility
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5
Q

which 2 malarial forms have different resistance patterns in different geographical areas?

A

P. falciparum

P. vivax

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6
Q

how do you treat uncomplicated malaria?

A

use oral antimalarials

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7
Q

Complicated malariae tx.?

A

Tx aggressively with parenteral antimalarials.

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8
Q

Major antimalarial drugs

A

Choroquine (not for severe forms, prophylaxis)
Quinine and quinidine (for severe, major AEs)
primaquine (for liver hypnozoites)
Atovaquone
Sulfadoxine-pyrimethamine
Doxycycline
Aryemisinins

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9
Q

Chloroquine:

DOC?

A

DOC:

  • as treatment and prophylaxis for P. vivax an ovale
  • Non-falciparum and sensitive uncomplicated falciparum malaria.
  • preferred chemoprophylactic agent in areas w/out resistant falciparum malaria.
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10
Q

Chloroquine:
Antimalarial action?
MOA?

A

Antiamalarial action:

  • Highly effective agains blood parasites
  • NOT active against liver stage

MOA:

  • Concentrates in parasite food vacuoles
  • Prevents biocrystallization of hemolobin breakdown product heme to non-toxix HEMOZOIN
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11
Q

Chloroquine:
PK:
Resistance:

A

PK:

  • ORAL
  • t1/2: 3-5 days (take once weekly)

Resistance
- P. falciparum: mutations in putative transport. PfCRT are common.

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12
Q

Chloroquine:

- AE?

A
  • WELL TOLERATED
  • pruritis in africans
  • Nausea, vomiting, abdominal pain, headache, anorexia , malaise, blurring of vision, urticaria (uncommon)
  • hemolysis (G6PD-defecient people)
  • can cause electrocardiographic changes!
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13
Q

Chloroquine:
CI:

A
  • patients with psoriasis or porphyria (may ppt attacks)
  • retinal or visual field abnomalities
  • SAFE IN PREGNANCY AND YOUNG
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14
Q

Quninine and Quinidine (stereoisomer):

  • FIRST LINE FOR?
  • resistance?
  • CA?
A
  • 1st line for: therapies for severe falciparum disease
  • resistance is uncommon

CA:

  • Parenteral tx. for severe falciparum malaria (QUINIDINE)
  • Oral tx. of falciparum malaria (alternative in chloroquine-resistant areas) (Quinine)
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15
Q

Quninine and Quinidine (stereoisomer):
Antimalarial action:
MOA:

A

Antimalarial Action
• Rapidly-acting, highly effective against blood parasites
• NOT active against liver stage parasites

MOA
• Depresses O2 uptake and carbohydrate metabolism
• Intercalates into DNA, disrup gp p ting parasite’s replication and
transcription

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16
Q

Quninine and Quinidine (stereoisomer):
PK?
Resistance

A

Pharmacokinetics
• Quinine: oral treatment of uncomplicated malaria
• Quinidine: IV treatment for severe malaria
Resistance
• Likely to be increasing problem
• Already common in some areas of South-east Asia

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17
Q

Quninine and Quinidine (stereoisomer):

AE?

A
  • Cinchonism: tinnitus headache nausea dizziness flushing & visual disturbances
  • Hypersensitivity: skin rashes, urticaria, angioedema. bronchospasm
  • Hematologic abnormalities: hemolysis (G6PD deficiency), leukopenia, agranulocytosis, thrombocytopenia
  • Hypoglycemia: stimulation of insulin release
  • Uterine contractions: still used in treatment of severe falciparum malaria in pregnancy
  • Severe hypotension: too rapid IV infusion
  • ECG abnormalities: QT prolongation
  • Blackwater fever: hemolysis & hemoglobinuria (likely hypersensitivity reaction)
18
Q

Quninine and Quinidine (stereoisomer):

CI:

A

Discontinue if signs of:

  • severe cinchonism
  • hemolysis
  • hypersensivity

Avoid in patients with:
- auditory adn visual problems

Use with caution in patients with underlying cardiac abdnormalities (QT prolongation)

  • Do not use concurrently with mefloquine
  • can raise plasma levels of warfarin and digoxin
  • reduce dose in renal insufficiency

PREGNANCY
- FDA Cat. C (however benefits do often outweigh risks in complicated malaria).

19
Q

Mefloquine
similar to?
MOA

A

Effective agains many choroquine resistant strains
chemically related to quinine.

MOA: Kills parasite in blood

20
Q

Mefloquine
Clinical applications
Tx?
Combination w/ what drug to treat malaria in SE Asia?

A

• Chemoprophylaxis: effective against most strains of P. falciparum and P.vivax

* Currently only medication recommended for chemoprophylaxis in pregnant women in chloroquine-resistant areas resistant areas***

  • Treatment : can be used to treat mild to moderate acute malaria caused by P.falciparum and P.vivax
  • Mefloquine + artesunate used in treatment of uncomplicated malaria in regions of Southeast Asia
21
Q

Melfoquine
PK?
Resistance?

A

Oral only
t1/2 = 20 days (weekly prophylactic dosing)

Resistance is uncommon but has been reported
- associated w/ resistance to quinine but not chloroquine!

22
Q

Mefloquine AE:

A

Serious neurological and psychiatric toxicities:
- Dizziness, loss of balance, ringing in the ears, anxiety , depression, hallucinations

Weekly dosing
- Nausea, vomiting, diarrhea, dizziness, sleep and behavioral disturbances, rash

Higher treatment doses:
- leukocytosis, thrombocytopenia, aminotransferase elevations, arryhthmias, bradycardia

23
Q

Mefloquine CI

BLACK BOX WARNING!

A

•Patients with history of: Epilepsy, psychiatric disorders, arrhythmia,
cardiac conduction defects sensitivity to related cardiac conduction defects, sensitivity to related
drugs
• DO NOT coadminister coadminister with quinine, quinidine or halofantrine
• Considered safe in young children & pregnancy

24
Q

Primaquine clinical application:

A

• Drug of choice for eradication of dormant liver forms of P. vivax and P. ovale (only available agent).

  • chemoprophylaxis (all strains)
  • Therapy of acute Therapy of acute vivax and ovale malaria malaria
  • Terminal prophylaxis of vivax and ovale malaria
  • Chemoprophylaxis: protection against falciparum & vivax (toxicities are a concern – reserved for when other drugs cannot be used)
25
Q

Primaquine PK:

Ressistance?

A

Oral
metabolites have less antimalarial activity but more potential for inducing hemolysis

May require therapy to be repeated and dose to be increased!

26
Q

Primaquine AE:

  • G6PD interactions?
  • G6PD def.?
  • pregnancy?
A
  • WELL TOLERATED
  • Hemolysis or methemoglobinemia (especially in G6PD deficient patients)
  • Primaquine oxidizes GSH to GSSG. Therefore less GSH is available to neutralize toxic compounds.

For severe G6PD def. patients withhold and treat relapses.

  • CI’d in pregnant because fetus is G6PD deficient.
27
Q

MALARONE
what 2 drugs make it up?
CA?
Antimalarial action?

A

Atovaquone + proguanil

Clinical Applications:
• Treatment; prophylaxis of P. falciparum

Antimalarial Action
• Active against tissue and erythrocytic schizonts
• Chemoprophylaxis can be started 1-2 days before travel and discontinued 1 week after exposure

28
Q

MALARONE
MOA?
PK?
AE?

A

MOA
• Disrupts mitochondrial electron transport

Pharmacokinetics
• Oral only

Adverse Effects 
• Generally well tolerated
• Abdominal pain, nausea, vomiting, diarrhea, headache,
rash
• Do not use in pregnancy
29
Q

Inhibitorrs of folate synthesis

- how are they used?

A

Primethamine
Proguanil
sulfodoxine
- used in combination regimen

30
Q

Inhibitorrs of folate synthesis: CA

  1. Chemoprophylaxis
  2. Intermittent Preventive Therapy:
  3. Treatment of chloroquine-resistant falciparum malaria
A
  1. only in combination. Proguanil + chloroquine = no longer recommended
  2. high-risk patients receive intermittent therapy regardless of infection status
  3. pyrimethamine-sulfadoxine commonly used. DO NOT use for severe malaria
31
Q

Inhibitors of folate synthesis: Antimalarial action:

  1. Pyrimethamine + proguanil
  2. Proguanil
  3. sulfonamides
A
  1. Act slowly against erythrocytic forms of all
    malaria species
  2. Some activity against hepatic forms
  3. Weakly active against erythrocytic schizonts
32
Q

Inhibitors of folate synthesis PK

AE:

A

Oral
resistance common for P. falciparum

AE:
• Well tolerated (GI problems rashes itching) (GI problems, rashes, itching)
• Proguanil (mouth ulcers, alopecia = rare)
• Pyrimethamine-Sulfadoxine (erythema multiforme, Steven-Johnson syndrome, toxic epidermal necrolysis)
• Sulfadoxine (hematologic, GI, CNS, dermatologic & renal toxicity)

Pregnancy:
• Proguanil = safe
• Pyrimethamine-sulfadoxine = safe

33
Q

Doxycycline

A
  • Active against erythocytic schizonts of all human malaria parasites
  • NOT active against liver stage

Clinical Applications
• Used to complete treatment for severe falciparum malaria (given along with quinine) after initial treatment with quinine, quinidine or artesunate
• Chemoprophylaxis against most forms: must be taken daily

34
Q

Doxycycline AE:

A
  • GI, candidal candidal vaginitis PHOTOSENSITIVITY
  • Discoloration & hypoplasia of teeth, stunting of growth
  • Fatal hepatotoxicity (in pregnancy)
  • DO NOT use in pregnancy or children
35
Q

Artemisinin PK for the different types?

Coartem is a combination of ?

A

Derived from qinghaosu qinghaosu plant
• Artesunate : oral, IV, IM & rectal admin
• Artemether: oral, IM & rectal admin
• Dihydroartemisinin: oral admin
• Coartem = artemether + lumefantrine

36
Q

Artemisinin Clinical App.

MOA

PK?

A

Treatment of severe falciparum malaria (given IV)

  • NO EFFECT on hepatic stages
  • dont use as single agen (resistance)

MOA
• Appears to act by binding iron, breaking down peroxide bridges leading to generation of free radicals that damage bridges leading to generation of free radicals that damage

PK:
very short t1/2 (IV therapy must be followed by longer acting agent once patient is able to tolerate oral therapy)

If used alone, artesunate must be used 5-7 days (otherwise recurrent parasitemia results)

37
Q

Artemisinin AE

A
  • Overall remarkably safe (nausea vomiting diarrhea)
  • Very high doses: neurotoxicity, QT prolongation
  • More evidence for use in 2nd and 3rd trimesters of pregnancy
  • In 1st trimester can be used for treatment of severe malaria
38
Q

Other Anti malarials

A

Clindamycin
- can be used as an alternate tp doxycycline

Halofantrine:
• Effective against erythrocytic stages of all parasites
• Use is limited by irregular absorption & cardiac toxicity Use is limited by irregular absorption & cardiac toxicity
• Teratogenic

Lumefantrine
• Effective against erythrocytic stages of all parasites
• Available only as fixed-dose combination with artemether
• Causes minor QT prolongation (clinically insignificant) Causes minor QT prolongation (clinically insignificant)
• Well tolerated

39
Q

Tx Guidelines for Uncomplicated malaria:

  1. P falciparum w/ no resistance DOC?
  2. P. falciparum w/ chloroquine resistance or unknown
  3. P.malariae all regions (no known resistance)
A
  1. Chloroquine or hydroxychloroquine
    2: i. Atovaquone-proguanil (malarone)
    ii. Artemehter-lumefantrine (co-artem)
    iii. Quinine + doxycycline
    iv. mefloquine
  2. Chloroquine/hydroxychloroquine
40
Q

Tx Guidelines for Uncomplicated malaria:

1. P. vivax or P.ovale all regions little reported resistance.

A
  1. chloroquine + primaquine

2. Hydrochloroquine + primaquine

41
Q

Tx Guidelines for Uncomplicated malaria:

P. vivax-chloroquine resistance

A
  1. quinine + doxy + Primaquine
  2. Atovaquone-proguanil + primaquine
  3. Mefloquine + primaquine

Pharmacology (27 decks)

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