Malaria tablets: doxycycline

Doxycycline

Prevention of malaria caused by Plasmodium falciparum.

Formulation

• doxycycline: 100mg or 200mg tablets are available
• a tablet cutter can be used to cut the tablets into half 
• no liquid formulation available

Half- Life

• 15-24 hours

Dosing schedule

• adults and children >50kg: 100 mg per day
• children from 8 years: 2mg/kg/day to a maximum of 100 mg/day
• duration: daily, to start 1-2 days before entering risk zone until 28 days after leaving endemic area

Administration

• take with enough liquid or during a meal to reduce the risk of oesophageal ulcers
• avoid administration with antacids (containing aluminium, calcium, magnesium, zinc, iron salts or bismuth) as much as possible since it can impair the absorption of doxycycline

Protection

• between 92% and 96% for P. falciparum 
• 98% for primary P. vivax infection.

Contra- indications

• hypersensitivity to tetracyclines
• depression and epilepsy are not contra-indications
• can be used in those known to be G6PD-deficient

Precautions

• carbamazepine and phenytoin: increase the metabolism of doxycyline
• tetracyclines possibly enhance the anticoagulant effect of coumarins (e.g., warfarin)

Breastfeeding

• can be used only if no alternative available
• according to the medication leaflet it is contraindicated during breastfeeding. However the American Academy of paediatrics and the CDC say it is compatible with breastfeeding since it is excreted at a low concentration of 30-40% of that found in maternal blood and it is thought that the drug absorption by infants is inhibited by the calcium in breast milk. Furthermore, tetracycline was undetectable in breastfed infants whose mothers were taking tetracycline.

Pregnancy

• can be used in the first trimester of pregnancy but the full course (including 28 days after travel) must be completed before 15 weeks’ gestation
• can cross the placenta and can cause discoloration of teeth when given during the second or third trimester of pregnancy

Children below the age of 8 year

• prolonged use of doxycycline in children below the age of 8 year is contra-indicated due to the potential risk of yellow tooth discolouration and dental enamel hypoplasia with tetracyclines
• in the early 1960s, dental side-effects were associated with the use of tetracycline, the incidence was greater with high doses of tetracycline and long term use. Doxycycline was developed later and is a newer medication in the tetracycline class but was labelled with the same side-effects as the earlier tetracyclines. However, recent studies report little or no effects of doxycycline on tooth staining or dental enamel hypoplasia in short term (3-10 days) use of doxycycline in children <8 years.
  Since currently no data on long term use is available the recommendations to avoid doxycycline as malaria chemoprophylaxis for young children travellers below the age of 8 year remains unchanged.

Side effects

• vulvovaginitis (candida)
• photosensitivity, so avoidance of excessive sun exposure and the correct use of high SPF sunscreen
• gastric and intestinal discomfort

Advantages and disadvantages

Additional information

• Wikitropica: background information on malaria for medical prefessionals
• Malaria Factsheet (WHO 2022)
• About Malaria (CDC 2022)
• CDC Yellow book: Travel-Related Infectious Diseases - Malaria (CDC 2023)

References

• Tan at al.  Centers for Disease Control and Prevention. Doxycycline for malaria chemoprophylaxis and treatment: report from the CDC expert meeting on malaria chemoprophylaxis. Am J Trop Med Hyg. 2011 Apr
• Todd et al. No visible dental staining in children treated with doxycycline for suspected Rocky Mountain Spotted Fever. J Pediatr. 2015 May