How the dose is calculated
Doxycycline is dosed in mg/kg/day. Standard treatment dosing is divided every 12 hours; malaria chemoprophylaxis uses a lower once-daily dose. Tetracyclines can stain developing teeth, so use is generally avoided under age 8 except for specific indications with no safer alternative (e.g. severe rickettsial or vector-borne disease) — confirm current age-specific guidance before prescribing.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Standard infection | 4 mg/kg/day | every 12h (2×/day) | 200 mg/day |
| Malaria prophylaxis | 2 mg/kg once daily | once daily | 100 mg/day |
Doxycycline is generally avoided in children under 8 years because of the risk of permanent tooth discoloration, except when treating specific infections (e.g. severe rickettsial disease, leptospirosis, anthrax exposure) where no safer alternative exists — recent guidance suggests short courses carry lower risk than previously believed, but this remains a specialist decision, not a routine one.
Clinical use
- Doxycycline is the treatment of choice for many rickettsial diseases (e.g. Rocky Mountain spotted fever, scrub typhus) even in young children, since delayed treatment carries far greater risk than the tooth-staining concern.
- Also used for malaria chemoprophylaxis in travellers to chloroquine-resistant areas, leptospirosis, and as an alternative for atypical respiratory pathogens.
- Should be taken with a full glass of water and the patient should remain upright for 30 minutes afterward, to reduce the risk of oesophageal irritation/ulceration.
- Photosensitivity is common — advise sun protection during treatment.
Frequently asked questions
Is doxycycline safe for young children?
It's generally avoided under age 8 because of a risk of permanent tooth discoloration, but it is still used at any age for specific severe infections (like rickettsial disease) where no safer alternative exists and delayed treatment is more dangerous than the tooth-staining risk.
What is doxycycline used for in malaria prevention?
It's one of the standard chemoprophylaxis options for travellers to areas with chloroquine-resistant malaria, taken once daily starting before travel and continued for 4 weeks after leaving the risk area.
Why should doxycycline be taken with a full glass of water?
Doxycycline capsules/tablets can irritate or ulcerate the oesophagus if they don't pass through quickly — a full glass of water and staying upright afterward reduces this risk.
Does doxycycline make skin more sensitive to sun?
Yes — photosensitivity is a recognised side effect, so sun protection (sunscreen, protective clothing) is recommended during treatment.
References
- American Academy of Pediatrics. Update on Doxycycline Use in Children of All Ages. Pediatrics. 2015.
- Centers for Disease Control and Prevention. Yellow Book — Malaria Chemoprophylaxis.
- British National Formulary for Children (BNFc) — Doxycycline.