Chemoprophylaxis Flashcards
Altitude Illness Doses of the agents
Acetazolamide
AMS and HACE Prevention 125 mg twice a day; 250 mg twice a day if >100 kg. Pediatric: 2.5 mg/kg every 12 h
AMS Treatment 250 mg twice a day Pediatric: 2.5 mg/kg every 12 h
Dexamethasone:
AMS, HACE prevention 2 mg every 6 h or 4 mg every 12 h
Pediatric: should not be used for prophylaxis
AMS, HACE treatment AMS: 4 mg every 6 h HACE: 8 mg once, then 4 mg every 6 h
Pediatric: 0.15 mg/kg/dose every 6 h up to 4 mg
Nifedipine:
HAPE Prevention: 30 mg SR version every 12 h, or 20 mg SR version every 8 h
HAPE Treatment 30 mg SR version every 12 h, or 20 mg SR version every 8 h HAPE prevention
Tadalafil 10 mg bid
sildenafil 50 mg Q8H
Salmeterol 125 mcg bid (not used as monotherapy)
Summary of Acetazolamide
Acetazolamide prevents AMS when taken before ascent and can speed recovery if taken after symptoms have developed. The drug works by acidifying the blood, which causes an increase in respiration and thus aids acclimatization. An effective adult dose that minimizes the common side effects of increased urination and paresthesias of the fingers and toes is 125 mg every 12 hours, beginning the day before ascent and continuing the first 2 days at altitude, or longer if ascent continues. Allergic reactions to acetazolamide are uncommon. As a nonantimicrobial sulfonamide, it does not cross-react with antimicrobial sulfonamides. However, it is best avoided by people with history of anaphylaxis to any sulfa. People with history of severe penicillin allergy have occasionally had allergic reactions to acetazolamide. The pediatric dose is 5 mg/kg/day in divided doses, up to 125 mg twice a day.
Summary of Dexamethasone
Dexamethasone is effective for preventing and treating AMS and HACE, and perhaps HAPE as well. Unlike acetazolamide, if the drug is discontinued at altitude before acclimatization, rebound can occur. Acetazolamide is preferable to prevent AMS while ascending, with dexamethasone reserved for treatment, as an adjunct to descent. The adult dose is 4 mg every 6 hours. An increasing trend is to use dexamethasone for “summit day” on high peaks such as Kilimanjaro and Aconcagua, to prevent abrupt altitude illness.
Summary of Nifedipine
Nifedipine prevents HAPE and ameliorates it as well. For prevention, it is generally reserved for people who are particularly susceptible to the condition. The adult dose for prevention or treatment is 30 mg of extended release every 12 hours, or 20 mg every 8 hours.
Summary of other medications for altitude illness
Phosphodiesterase-5 inhibitors can also selectively lower pulmonary artery pressure, with less effect on systemic blood pressure. Tadalafil, 10 mg twice a day, during ascent can prevent HAPE and is being studied for treatment. When taken before ascent, gingko biloba, 100–120 mg twice a day, was shown to reduce AMS in adults in some trials, but it was not effective in others, probably due to variation in ingredients. Ibuprofen 600 mg every 8 hours was recently found to help prevent AMS, although it was not as effective as acetazolamide. However, it is nonprescription, inexpensive, and well tolerated
Leptospirosis chemoprophylaxis
until further data become available, CDC recommends chemoprophylaxis with doxycycline (200 mg orally, weekly), begun 1–2 days before and continuing through the period of exposure for people at high risk of leptospirosis. Doxycycline is not recommended for pregnant women or children aged
Malaria - Atovaquone-proguanil dosing
Adult tablets contain 250 mg atovaquone and 100 mg proguanil hydrochloride.
1 adult tablet orally, daily
Pediatric tablets contain 62.5 mg atovaquone and 25 mg proguanil hydrochloride. 5–8 kg: 1/2 pediatric tablet daily >8–10 kg: 3/4 pediatric tablet daily >10–20 kg: 1 pediatric tablet daily >20–30 kg: 2 pediatric tablets daily >30–40 kg: 3 pediatric tablets daily >40 kg: 1 adult tablet daily
Begin 1–2 days before travel to malarious areas. Take daily at the same time each day while in the malarious area and for 7 days after leaving such areas. Contraindicated in people with severe renal impairment (creatinine clearance <30 mL/min). Atovaquone-proguanil should be taken with food or a milky drink. Not recommended for prophylaxis for children weighing <5 kg, pregnant women, and women breastfeeding infants weighing <5 kg. Partial tablet doses may need to be prepared by a pharmacist and dispensed in individual capsules
Malaria - Chloroquine dosing
300 mg base (500 mg salt) orally, once/week 5 mg/kg base (8.3 mg/kg salt) orally, once/week, up to maximum adult dose of 300 mg base begin 1–2 weeks before travel to malarious areas. Take weekly on the same day of the week while in the malarious area and for 4 weeks after leaving such areas. May exacerbate psoriasis.
Malaria - Doxycycline Dosing
100 mg orally, daily ≥8 years of age: 2.2 mg/kg up to adult dose of 100 mg/day Begin 1–2 days before travel to malarious areas. Take daily at the same time each day while in the malarious area and for 4 weeks after leaving such areas. Contraindicated in children
Malaria - Hydroxychloroquine Sulfate dosing
310 mg base (400 mg salt) orally, once/week 5 mg/kg base (6.5 mg/kg salt) orally, once/week, up to maximum adult dose of 310 mg base Begin 1–2 weeks before travel to malarious areas. Take weekly on the same day of the week while in the malarious area and for 4 weeks after leaving such areas.
Malaria - Mefloquine dosing
228 mg base (250 mg salt) orally, once/week ≤9 kg: 4.6 mg/kg base (5 mg/kg salt) orally, once/week
>9-19 kg: 1/4 tablet once/week >19-30 kg: 1/2 tablet once/week >30-45 kg: 3/4 tablet once/week >45 kg: 1 tablet once/week
Begin ≥2 weeks before travel to malarious areas. Take weekly on the same day of the week while in the malarious area and for 4 weeks after leaving such areas.
Contraindicated in people allergic to mefloquine or related compounds (quinine, quinidine) and in people with active depression, a recent history of depression, generalized anxiety disorder, psychosis, schizophrenia, other major psychiatric disorders, or seizures. Use with caution in persons with psychiatric disturbances or a previous history of depression. Not recommended for persons with cardiac conduction abnormalities.
Malaria Primaquine dosing prophylaxis
30 mg base (52.6 mg salt) orally, daily 0.5 mg/kg base (0.8 mg/kg salt) up to adult dose orally, daily Begin 1–2 days before travel to malarious areas. Take daily at the same time each day while in the malarious area and for 7 days after leaving such areas. Contraindicated in people with G6PD deficiency. Also contraindicated during pregnancy and lactation, unless the infant being breastfed has a documented normal G6PD level.
Malaria primaquine Presumptive antirelapse therapy
30 mg base (52.6 mg salt) orally, daily for 14 days after departure from the malarious area 0.5 mg/kg base (0.8 mg/kg salt) up to adult dose orally, daily for 14 days after departure from the malarious area Indicated for people who have had prolonged exposure to P. vivax, P. ovale, or both. Contraindicated in people with G6PD deficiency. Also contraindicated during pregnancy and lactation, unless the infant being breastfed has a documented normal G6PD level.
Traveller’s Diarrhea prophylaxis - nonantimicrobial
The primary agent studied for prevention of TD, other than antimicrobial drugs, is bismuth subsalicylate (BSS), which is the active ingredient in Pepto-Bismol. Studies from Mexico have shown this agent (taken daily as either 2 oz of liquid or 2 chewable tablets 4 times per day) reduces the incidence of TD by approximately 50%. BSS commonly causes blackening of the tongue and stool and may cause nausea, constipation, and rarely tinnitus. BSS should be avoided by travelers with aspirin allergy, renal insufficiency, and gout and by those taking anticoagulants, probenecid, or methotrexate. In travelers taking aspirin or salicylates for other reasons, the use of BSS may result in salicylate toxicity. BSS is not generally recommended for children aged 3 weeks. Because of the number of tablets that need to be carried and the 4 times per day dosing, BSS is not commonly used as prophylaxis for TD. The use of probiotics, such as Lactobacillus GG and Saccharomyces boulardii, has been studied in the prevention of TD in small numbers of people. Results are inconclusive, partially because standardized preparations of these bacteria are not reliably available. Some people report beneficial outcomes using bovine colostrum as a daily prophylaxis agent for TD. However, commercially sold preparations of bovine colostrum are marketed as dietary supplements that are not Food and Drug Administration (FDA) approved for medical indications. Because no data from rigorous clinical trials demonstrate efficacy in controlled trials, there is insufficient information to recommend the use of bovine colostrum to prevent TD.
Traveller’s Diarrhea prophylaxis - antimicrobial
Prophylactic antibiotics are effective in the prevention of TD. Controlled studies have shown that diarrhea attack rates are reduced by 90% or more by the use of antibiotics. The prophylactic antibiotic of choice has changed over the past few decades as resistance patterns have evolved. Agents such as trimethoprim-sulfamethoxazole and doxycycline are no longer considered effective antimicrobial agents against enteric bacterial pathogens. The fluoroquinolones have been the most effective antibiotics for the prophylaxis and treatment of bacterial TD pathogens, but increasing resistance to these agents, mainly among Campylobacter species, may limit their benefit in the future. A nonabsorbable antibiotic, rifaximin, is being investigated but is not currently approved by the FDA for its potential use in TD prophylaxis. In one study, rifaximin reduced the risk for TD in travelers to Mexico by 77%. At this time, prophylactic antibiotics should not be recommended for most travelers. Prophylactic antibiotics afford no protection against nonbacterial pathogens and can remove normally protective microflora from the bowel, rendering a traveler more susceptible to infection with resistant bacterial pathogens. Additionally, the use of antibiotics may be associated with allergic or adverse reactions in a certain percentage of travelers and may potentially contribute to drug resistance. The use of prophylactic antibiotics should be weighed against the result of using prompt, early self-treatment with antibiotics when TD occurs, which can limit the duration of illness to 6–24 hours in most cases. Prophylactic antibiotics may be considered for short-term travelers who are high-risk hosts (such as those who are immunosuppressed) or who are taking critical trips during which even a short bout of diarrhea could affect the trip.
