How much doxycycline should be taken after a tick bite? - briefly
The standard prophylactic regimen is 100 mg of doxycycline taken orally once daily for 21 days, initiated within 72 hours of the bite. This dosage is recommended for tick exposures in regions where Lyme disease risk is significant.
How much doxycycline should be taken after a tick bite? - in detail
The standard prophylactic regimen for a tick exposure that carries a risk of Lyme disease is a single dose of 200 mg doxycycline taken orally within 72 hours of the bite. This recommendation applies to adults and children weighing at least 45 kg (approximately 99 lb). For individuals under that weight threshold, the dose is reduced to 4 mg per kilogram of body weight, not exceeding 200 mg, administered as a single dose within the same time frame.
Key considerations:
- Timing: The dose must be taken no later than three days after the bite; effectiveness declines sharply after this window.
- Geographic risk: Prophylaxis is advised only in regions where the prevalence of infected ticks exceeds 20 % and where the tick species is known to transmit Borrelia burgdorferi.
- Contraindications: Pregnant or lactating women, and persons with a known hypersensitivity to tetracyclines, should not receive doxycycline. Alternative agents (e.g., amoxicillin 2 g single dose) may be considered in these cases.
- Adverse effects: Common side effects include mild gastrointestinal upset and photosensitivity; patients should avoid prolonged sun exposure for 24 hours after dosing.
- Follow‑up: If the tick was attached for more than 36 hours, a rash or flu‑like symptoms develop, or the bite occurred in a high‑risk area, a full treatment course of doxycycline 100 mg twice daily for 10‑21 days is indicated, regardless of the single‑dose prophylaxis.
In summary, a single 200 mg oral dose within 72 hours is the evidence‑based approach for most adults and larger children, with weight‑adjusted dosing for smaller children and alternative regimens for contraindicated populations.