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Doxycycline

Antibioticprescriptionoral · inferred

Second-generation tetracycline antibiotic with broad-spectrum activity including atypicals (Chlamydia, Mycoplasma, Rickettsia), spirochetes (Lyme), and malaria prophylaxis. Superior oral absorption to tetracycline (93% bioavailability), minimally affected by food. Also used for acne, rosacea, and periodontal disease due to anti-inflammatory matrix metalloproteinase inhibition. Photosensitivity and esophageal irritation are key side effects.

Projected serum levels — 100 mg, twice daily

Doxycycline
Doxycycline modeled serum levels, 100 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 62.5 125 188 250 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Doxycycline modeled serum levels with a loading dose of 268 mg, then 100 mg twice daily The first dose is larger so levels approach steady state faster. 0 62.5 125 188 250 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 100 mg twice daily (oral).

Loading schedule: 268 mg on day 1, then 100 mg twice daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 231 mg, trough ≈ 157 mg body load. Population-based estimate over 15 days for a 100 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Antibiotic
Route modeled
Oral
Model confidence
inferred
Half-life
18 h
Common dose
100 mg
Suggested maximum
200 mg/day
Reference dose range
40–200 mg (single dose)
Suggested cadence
twice daily
Validated against
100 mg oral — Cmax 1.8 mg/L at 2 h

Documented interactions

  • caution
    Ethinyl Estradiol + Doxycycline Depletion

    Tetracycline antibiotics may reduce enterohepatic recirculation of ethinyl estradiol by disrupting gut flora. Transient reduction in EE levels may theoretically reduce contraceptive efficacy.

  • caution
    Iron (Bisglycinate) + Doxycycline Chelation

    Doxycycline (tetracycline antibiotic) forms insoluble complexes with Iron (Bisglycinate) in the GI tract, reducing absorption of both.

  • caution
    Magnesium Citrate + Doxycycline Chelation

    Doxycycline (tetracycline antibiotic) forms insoluble complexes with Magnesium Citrate in the GI tract, reducing absorption of both.

  • caution
    Magnesium Glycinate + Doxycycline Chelation

    Doxycycline (tetracycline antibiotic) forms insoluble complexes with Magnesium Glycinate in the GI tract, reducing absorption of both.

  • caution
    Magnesium L-Threonate (Magtein) + Doxycycline Chelation

    Doxycycline (tetracycline antibiotic) forms insoluble complexes with Magnesium L-Threonate (Magtein) in the GI tract, reducing absorption of both.

  • caution
    Selenium (Selenomethionine) + Doxycycline Chelation

    Doxycycline (tetracycline antibiotic) forms insoluble complexes with Selenium (Selenomethionine) in the GI tract, reducing absorption of both.

Serum checks 25 modeled interaction pairings for doxycycline across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Pharmacokinetics and tissue penetration of doxycycline Agwuh KN, MacGowan A · Journal of Antimicrobial Chemotherapy, 2006 DOI

    Comprehensive PK review establishing doxycycline half-life of 16-22 hours, 93% oral bioavailability, excellent tissue penetration including lung and bone, and predominantly fecal elimination (chelated in gut).

  2. Doxycycline for malaria chemoprophylaxis and treatment: report from the CDC expert meeting on malaria chemoprophylaxis Tan KR et al. · American Journal of Tropical Medicine and Hygiene, 2011 DOI

    Expert consensus review confirming doxycycline 100 mg daily as effective malaria prophylaxis with 92-96% protective efficacy, well-tolerated for long-term use.

2 published studies referenced in the app, each with a plain-language summary.