What is the recommended dose and frequency of doxycycline (antibiotic) for preventing Lyme disease after a tick bite?

From the Guidelines

The recommended dose of doxycycline for preventing Lyme disease after a tick bite is a single 200 mg dose taken by mouth, ideally within 72 hours of tick removal, as stated in the 2021 clinical practice guidelines by the Infectious Diseases Society of America (IDSA) 1. This single-dose prophylactic treatment is only recommended when all of the following conditions are met:

• the attached tick is identified as an adult or nymphal Ixodes scapularis (deer tick)
• the tick has been attached for at least 36 hours
• prophylaxis can be started within 72 hours of tick removal
• the local rate of infection of ticks with Borrelia burgdorferi is at least 20% This approach is not recommended for pregnant women or children under 8 years old due to potential effects on bone and tooth development, as noted in earlier guidelines 1. The single-dose regimen works by eliminating the bacteria before it can establish infection, as the spirochete that causes Lyme disease typically requires more than 36 hours of attachment to transmit from tick to human. If you've already developed symptoms of Lyme disease (such as the characteristic bull's-eye rash, fever, or joint pain), a full treatment course of doxycycline would be needed instead of prophylaxis. Key points to consider include:
• The dose for children is 4.4 mg/kg (up to a maximum dose of 200 mg) 1
• Doxycycline is relatively contraindicated in pregnant women and children < 8 years old 1
• Prophylaxis after I. pacificus bites is generally not necessary due to low infection rates with B. burgdorferi 1

From the Research

Recommended Dose and Frequency of Doxycycline

• The recommended dose of doxycycline for preventing Lyme disease after a tick bite is a single dose of 200 mg 2, 3, 4, 5.
• The frequency of doxycycline administration is typically a one-time dose, given within 72 hours after the tick bite 2, 3, 4, 5.
• Studies have shown that a single dose of doxycycline can prevent the development of Lyme borreliosis after an Ixodes ricinus tick bite, with a relative risk reduction of 67% 3.
• The efficacy of treatment with a single dose of doxycycline has been reported to be 87% in preventing Lyme disease after an Ixodes scapularis tick bite 5.

Timing of Doxycycline Administration

• It is essential to administer doxycycline promptly after the tick bite, as the efficacy of prophylactic treatment decreases with time 6.
• A study in mice found that two treatments of doxycycline delivered on the day of tick removal protected 74% of test mice, while delayed treatment until 24 hours after tick removal protected only 47% of mice 6.
• The same study found that prophylactic treatment was totally ineffective when delivered 2 days or more after tick removal 6.

Adverse Effects and Considerations

• Treatment with doxycycline has been associated with more frequent adverse effects, primarily nausea and vomiting 5.
• The decision to administer doxycycline as prophylaxis should be made on a case-by-case basis, taking into account the individual's risk factors and medical history 4.