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PR3151 IC11 Immunization + Prophylaxis > Malaria Chemoprophylaxis > Flashcards

Malaria Chemoprophylaxis Flashcards

1
Q

What are the five different species of protozoan parasite, Plasmodium that causes malaria?

A
  1. P. falciparum
    - Prevalent
    - Most dangeous, highest rate of complications + morality
    - Highest rate of resistance to chloroquine
  2. P. malariae
  3. P. ovale
    - Possible dormancy
  4. P. vivax
    - Prevalent
    - Possible dormancy
  5. P. knowlesi
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2
Q

What are the clinical features of malaria?

A
  • Fever and chills
  • Sweat
  • Headache
  • Bodyache
  • Weakness
  • Nausea and Vomiting
  • Cough
  • Diarrhea
  • Abdominal pain
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3
Q

Why is malaria life-threatening?

A

Can progress to organ failure, sepsis, and death without timely treatment

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4
Q

In what areas are malaria more commonly transmitted and why?

A

Tropical and subtropical areas, breeding ground for mosquitoes

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5
Q

What is the mode of infection of malaria?

A

Bites of infected female Anopheles mosquitoes

Others: blood transfusion, organ transplant, vertical transmission
- *Recall that plasmodium can get into RBC

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6
Q

How does risk of transmission of malaria vary?

A
  1. Increases between dusk and dawn (night biter)
  2. Decreases during colder season/region (higher altitude, lower transmission)
  3. Decreases in desert
  4. Decrease at higher altitude ~105m above sea level
  5. Increase at end of rainy season
  6. Large urban areas usually free of transmission
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7
Q

Describe the Plasmodium life cycle (3 cycles)

A
  1. Human liver (exo-erythrocytic cycle)
    - Grow and multiply in liver cells
    - Can remain domain >4 weeks (P vivax, P ovale)
    - No clinical symptoms
  2. Human blood (erythrocytic cycle)
    - Grow and multiply in RBCs
    - Differentiation into sexual stages (gametocytes)
    - Presence of clinical symptoms
  3. Mosquito (sporogenic cycle)
    - Mate, growth, multiply, release
    - Inject sporozoites
    - Ingest gametocytes
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8
Q

Why do most of the malaria chemoprophylaxis drugs require 4 weeks continuation after return?

A

Many drugs target the blood phase (erythrocytic cycle)
=> Dormant plasmodium may be present in liver cells and only enter blood (erythrocytic cycle) after 4 weeks

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9
Q

What are the ABCDE for malaria prevention?

A

Awareness
- of risk, possibility of delayed onset, main symptoms
Bite prevention
Chemoprophylaxis
Diagnosis
- blood smear
Environments

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10
Q

Name the 4 malaria chemoprophylaxis drugs available in Singapore

A
  1. Atovaquone + Proguanil (Malarone)
  2. Chloroquine
  3. Doxycycline
  4. Mefloquine
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11
Q

What are some considerations when choosing antimalarial chemoprophylaxis?

A
  1. Travel itinerary
    - Chloroquine/Mefloquine resistance
  2. Medical history
    - Conditions: pregnancy, allergies, comorbidities
    - DDI
  3. Preferences
    - daily vs weekly
    - cost
  4. Travel departure date and duration
    - regimen to be started as early as 2 weeks before departure (to build up conc. in blood, to monitor for ADR development)
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12
Q

Describe the 3 types of malaria risk, and the corresponding type of prevention to be taken.

A

Type A: limited risk of malaria
- mosquito bite prevention

Type B: risk of non-falciparum malaria
- mosquito bite prevention
- atovaquone-proguanil, chloroquine, doxycycline, mefloquine

Type C: risk of falciparum malaria
- mosquito bite prevention
- atovaquone-proguanil, doxycline, mefloquine

*In areas with multidrug-resistant malaria, mefloquine no longer recommended as well

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13
Q

What is the dosing regimen for Atovaquone-proguanil (Malarone)?

A

1 adult tablet (Atorvaquone 250mg/Proguanil 100mg) daily

Start 1-2 days prior to trip, during trip, continue 7 days after return

*7 days because this drug active against liver phase
*Pediatric tablet available for babies >= 5kg

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14
Q

Atovaquone-proguanil (Malarone) should be taken with ________ to _________________

A

Taken with food and milky drinks to increase absorption and decrease GI discomfort (nausea, vomiting, stomach pain, diarrhea, headache, dizziness)

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15
Q

Atovaquone-proguanil (Malarone) is generally well tolerated except for some GI discomfort. However, it may not be the drug of choice because?

A

Most expensive option
Can cost ~$10 per tablet ($10 for each day)

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16
Q

Atovaquone-proguanil (Malarone) is contraindicated in?

A
  1. Hypersensitivity
  2. Renal impairment (CrCl <30ml/min)
  3. Pregnant, breastfeeding, babies <5kg
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17
Q

What are some DDIs with Atovaquone-proguanil (Malarone)?

A

Rifampicin (antiTB)
Metoclopromide (antiemetic)
Efavirenz (anti-HIV/AIDs)

These drugs can affect the concentration of Malarone

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18
Q

What is Atovaquone-proguanil (Malarone) product classification in Singapore? Can pharmacists cell this drug for malaria chemoprophylaxis?

A

POM with exemption

Pharmacist can supply (duration is based on the trip)

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19
Q

What is the dosing regimen for Chloroquine?

A

Chloroquine 300mg base (500mg salt)
=> two 250mg Chloroquine phosphate tablets (150mg base each) weekly in one dose

Start 1-2 weeks before departure, weekly during trip, continue 4 weeks after return

*Take on the same day every week

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20
Q

What are the contraindications for Chloroquine?

A
  1. Hypersensitivity
  2. Chloroquine resistance (in certain regions)
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21
Q

What are some ADRs and precautions when taking Chloroquine?

A

ADRs:
- GI discomfort: nausea, vomiting, stomach pain (*take with or after meals)
- Skin rash/itching

Precautions:
- Exacerbates psoriasis, seizure disorders, myasthenia gravis, auditory damage, liver impairment, G6PD deficiency (?)

22
Q

What are some DDIs associated with Chloroquine?

A

QT prolonging strong CYP3A4 inhibitors
- Macrolides: Clarithromycin
- Azoles: Voriconazole

23
Q

Can Chloroquine be used in children, pregnant, and breastfeeding women?

A

Yes

It can be used in ALL trimesters of pregnancy as well

24
Q

What is the product classification of Chloroquine in Singapore?

A

Pharmacy only

25
Q

What is the cost of Chloroquine per week?

A

20cents per tablet, one week 40cents

26
Q

In which instance would traveler no longer need to take additional Chloroquine for malaria chemoprophylaxis?

A

If traveler is already taking hydroxychloroquine chronically for rheumatologic conditions

Hydroxychloroquine is an antimalarial with anti-inflammatory and immunosuppressive effects

27
Q

What is the dosing regimen for Doxycycline?

A

Adult dose 100mg daily

Start 1-2 days prior to trip, during trip, continue for 4 weeks after return

28
Q

What are some special counseling points for the administration of Doxycyline?

A

Take with full glass of water, maintain upright for at least 30min
Do not take before bedtime

  • Because doxycyline is an acidic drug, can cause esophageal irritation and ulceration (esophagitis in serious cases)
29
Q

What are some ADRs and precaution with Doxycyline use?

A
  1. GI discomfort: nausea, vomiting, epigastric distress, esophageal irritation
  2. Photosensitivity: sunburns
  3. Vaginal candidiasis (yeast infection)

Others:
- Hepatotoxicity
- Superinfection

30
Q

In which groups of patient is Doxycycline contraindicated?

A
  1. Hypersensitivity
  2. Children <8yo
  3. Pregnant, breastfeeding

*Recall accumulation in calcified tissue affect primary dentition and bones

31
Q

What are some DDIs associated with use of Doxycyline?

A

Multi-valent ions (antacids, or dairy products) can form non-absorbable chelates, administration should be spaced apart

32
Q

What is the product classification for Doxycyline in Singapore? Can pharmacist sell this drug for chemoprophylaxis?

A

Prescription only

Pharmacists CANNOT sell

33
Q

Which malaria chemoprophylaxis is the cheapest option?

A

Doxycyline 10cents per tablet

34
Q

Patients may already be taking doxycyline for _____. This patients do not need additional medication when traveling.

A

Acne

35
Q

What are some additional prevention benefits of Doxycyline for travelers?

A

Doxycycline can also prevent additional infections such as:
- Rickettsiae (vector-borne) and Leptospirosis (water-borne)

Preferred for ppl going hiking, camping, wading, swimming in fresh waters

36
Q

What is the dosing regimen for Mefloquine?

A

Adult dose 250mg weekly, after meals

Start at least 1 week (preferably 2-3w) before departure, during trip, continue for 4 weeks after return

Why 2-3w before departure?
- look out for ADRs (concern for neuropsychiatric disorders)

37
Q

What are some ADRs of Mefloquine?

A
  1. GI discomfort: dizziness, fatigue, headache
  2. Insomnia, vivid dreams, neuropsychiatric disorders
38
Q

What are some contraindications to the use of Mefloquine?

A
  1. Hypersensitivity
  2. Mefloquine resistance
  3. Patient with history of psychiatric disorders
  4. Patient with history of convulsive disorders
  5. Patient with history of cardiac conduction abnormalities (as Mefloquine can cause QTc prolongation)
39
Q

Can Mefloquine be used in children, pregnancy, and breastfeeding?

A

Yes, can use in:

Children >5kg, pregnant, breastfeeding

40
Q

Which drug has DDI with Mefloquine?

A

Ketoconazole (incr the conc. of Mefloquine)

41
Q

What is the produce classification of Mefloquine in Singapore?

A

Pharmacy only

42
Q

Which of the 4 chemoprophylaxis drugs can be given to pregnant and breastfeeding women?

A

Chloroquine, Mefloquine

43
Q

Which of the 4 chemoprophylaxis drugs can be given to children?

A

Atovaquone + Proguanil: children >= 5kg
Chloroquine
Doxycyline: children >8yo
Mefloquine: children >5kg

44
Q

Which of the 4 chemoprophylaxis drugs can be sold by pharmacist without prescription from doctor?

A

Atovaquone + Proguanil (POM w exemption)
Chloroquine (P only)
Mefloquine (P only)

45
Q

What are some BARRIER precautions towards protection against mosquito bites?

A
  1. Stay indoors esp from dusk to dawn
  2. Wear clothing that exposes little skin
  3. Wear light-colored clothing
  4. Sleep under permethrin-impregnated bed net
  5. Sleep in sealed air con room or screened windows w fans
46
Q

What are some active ingredients in insect repellents?

A
  1. DEET (20-50% provides 6-12h protection, 30% provide 8-9h) (>50% does not offer more protection duration)
  2. Picaridin (at least 20%)
  3. Oil of lemon eucalyptus (OLE) or PMD
    - “Pure” oil of lemon eucalyptus is NOT recommended
  4. IR3535
  5. 2-undecanone
47
Q

Higher concentration of active ingredient of insect repellent provides ______

A

Longer duration of protection

**Heavy application and saturation are unnecessary for effectiveness

48
Q

What are some factors that may affect the efficacy and duration of protection of insect repellents?

A
  • Ambient temperature
  • Level of activity
  • Perspiration
  • Water exposure
  • Abrasive removal
49
Q

How long after trip should travelers monitor for malaria symptoms?

A

Malaria can be dormant for 1 week to 1 year, hence fever or flu-like symptoms can occur anytime within this time frame

Patient should seek medical attention and tell Dr travel history

50
Q

How long must travelers be excluded from blood donation after return from malaria risk country?

A

4 months

*Prevent transfusion of contaminated blood products

PR3151 IC11 Immunization + Prophylaxis (4 decks)

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