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A single dose of oral doxycycline within 72 hours of tick removal can reduce the risk of Lyme disease by roughly 87%. It is not given for every bite. The IDSA / AAN / ACR criteria, which CDC follows, require ALL of the following:
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The tick is identified as a blacklegged tick (Ixodes scapularis or Ixodes pacificus).
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The tick was attached for 36 hours or more (engorged appearance, or known timing).
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The bite occurred in a region where Lyme is highly endemic.
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Prophylaxis can be started within 72 hours of tick removal.
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Doxycycline is not contraindicated for the patient.
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Dose: 200 mg as a single oral dose for adults. For children, the recommended weight-based dose is 4.4 mg/kg up to a maximum of 200 mg.
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Prophylaxis is for Lyme only. It does not prevent anaplasmosis, babesiosis, or Powassan, so 30-day symptom monitoring still applies. Discuss with a clinician; do not self-prescribe.