The Problem With Single Dose Doxycycline For Tick Bites

Many people wonder what to do when they are bitten by a tick. Some may call their doctor and get a prescription for up to 200mg of doxycycline, the antibiotic used to treat Lyme disease. This protocol was reinforced by a recent article in the Journal of Emergency Medicine recommending it as a prophylactic for people bitten by a black-legged tick in areas where the rate of ticks infected with Lyme bacteria is greater than 20%.

Several problems that suggest this single dose of doxycycline may not be the best prophylactic for Lyme disease:

• The recommendation is based on bad science. The study claimed to show the effectiveness of single dose of doxycycline to prevent Lyme disease. The study actually shows a reduction in the appearance of erythema migrans (“bulls-eye”) rashes, a possible symptom of Lyme disease – but not the disease itself.
• The recommendation is based on only one study. The recommendation is based on a single study published in 2001 in the New England Journal of Medicine. The International Lyme and Associated Diseases Society’s (ILADS) guidelines note that the evidence supporting a single dose of doxycycline to prevent Lyme disease was “sparse, coming from a single study with few events, and, thus, imprecise.”
• The study only lasted 6 weeks. Symptoms of Lyme disease can begin “weeks to months” after a tick-bite. The subjects of the study were assessed at 3 and 6 weeks with no follow up. There is no way to know if the single dose of doxycycline prevented later manifestations of Lyme disease.
• Ticks can transmit more than Lyme disease. The study did not consider whether doxycycline is a prophylactic for other tick-borne illnesses such as Anaplasmosis, or Ehrlichiosis.
• Taking prophylactic doxycycline may result in negative blood tests for Lyme disease. Antibiotics may affect the immune response to Lyme bacteria, which could later result in a false-negative blood test for Lyme disease, potentially causing delays in diagnosis or treatment.

The IDSA guidelines recommend the single dose doxycycline as a prophylactic for Lyme disease.

The ILADS preferred prophylactic treatment for a person in an endemic area who discovers a feeding blacklegged (deer) tick is “100–200 mg of doxycycline, twice daily for 20 days” and they note “Other treatment options may be appropriate on an individualized basis.” (ILADS acknowledges this recommendation is based on “very low-quality evidence” and suggests that some patients may require higher doses of antibiotics, or individualized treatments.)

Coloradans who are bitten by a tick should consider all the information available about preventing Lyme disease as well as their own personal risk factors, and discuss their options with informed health-care providers.

Always contact a health-care provider immediately if becoming ill, as Lyme and other tick-borne diseases can be more effectively treated if diagnosed early.

*Adapted with permission from VTLyme!