What is the maximal dose of doxycycline (antibiotic) for adults?

Maximum Doxycycline Dose for Adults

The maximum daily dose of doxycycline for adults is 200 mg per 24-hour period for most bacterial infections, though specific acute situations may use higher single-day dosing regimens. 1, 2

Standard Maximum Dosing

• The FDA-approved maximum is 200 mg daily, typically administered as 100 mg every 12 hours for severe infections. 2
• The American Academy of Pediatrics and Infectious Diseases Society of America confirm that exceeding 200 mg daily may result in increased side effects without demonstrated additional efficacy. 1
• The FDA label explicitly warns that "exceeding the recommended dosage may result in an increased incidence of side effects." 2

Loading Dose Exceptions

While the daily maximum is 200 mg, certain protocols use higher first-day loading doses:

• A 200 mg loading dose on day 1 (administered as 100 mg every 12 hours) is standard, followed by 100 mg daily maintenance. 2
• Some experts recommend 200 mg as the first dose for community-acquired pneumonia to achieve adequate serum levels more rapidly, then continuing 100 mg twice daily. 3

Special Single-Dose Situations

Two specific scenarios use 200 mg as a single dose with strict limitations:

• STI post-exposure prophylaxis: 200 mg single dose within 72 hours, with the critical caveat of not exceeding 200 mg per 24 hours. 3, 1, 4
• Lyme disease prophylaxis: 200 mg single dose within 72 hours of tick removal. 3, 4

Historical High-Dose Regimen (No Longer Recommended)

• The FDA label mentions an obsolete regimen for uncomplicated gonococcal infections: 300 mg stat followed by another 300 mg one hour later (total 600 mg in one day). 2
• This regimen is not supported by current guidelines and should not be used given modern evidence showing no benefit beyond 200 mg daily. 1

Severe Infection Dosing

• For severe or chronic infections (particularly urinary tract), the FDA recommends 100 mg every 12 hours (total 200 mg daily) rather than increasing beyond this dose. 2
• Inhalational anthrax uses 100 mg twice daily (200 mg total) for 60 days. 1, 2

Common Pitfalls

• Never exceed 200 mg per 24-hour period for ongoing treatment—this applies even to severe infections where duration is extended, not dose. 1
• Patients should take doxycycline with adequate fluids and avoid lying down for 1 hour after administration to prevent esophageal irritation. 3, 2
• Separate dosing by at least 2 hours from dairy products, antacids, and supplements containing calcium, iron, magnesium, or sodium bicarbonate. 3