Section 15 · Monograph
Doxycycline
Reviewed Nov 2026FDA label
VibramycinTetracycline antibiotic
- Forms
- Tab/Cap: 50, 75, 100, 150mg | IV: 100mg
- Dose
- Lyme neuroborreliosis: 100mg twice daily PO/IV for 14-21 days
- MOA
- 30S ribosomal inhibition; adequate CNS penetration
Indications
- Rickettsial infections, respiratory and urinary infections, Lyme disease (early) and many othersFDA-labeled
Off-Label Uses
- Lyme neuroborreliosis (early neurologic Lyme disease) in adultsOff-label
- Neurosyphilis alternative for penicillin allergy (limited data)Off-label
Mechanism of Action
- Binds the 30S ribosomal subunit, inhibiting protein synthesis; lipophilic with adequate CNS penetration
Full Dosing
Adult / usual
- Lyme neuroborreliosis: 100mg PO or IV twice daily for 14-21 days
- Take with a full glass of water and remain upright to reduce esophagitis
- Separate from antacids, calcium, iron and magnesium by 2-3 hours
Contraindications
- Hypersensitivity to tetracyclines
Drug Interactions
- Divalent and trivalent cations impair absorption
- Carbamazepine, phenytoin and barbiturates shorten half-life
- Warfarin: increased INR; retinoids: intracranial hypertension
Adverse Effects
- Photosensitivity
- Esophagitis and GI upset
- Intracranial hypertension (pseudotumor cerebri)
- Tooth discoloration in children under 8 and with use in later pregnancy
- Hepatotoxicity (rare)
Monitoring Parameters
- Clinical response (cranial neuropathy, radiculopathy, meningitis)
- Headache or visual change suggesting intracranial hypertension
- Liver tests with prolonged use
Pregnancy & Lactation
- Avoid in second and third trimesters (tooth and bone effects)
- Short courses are acceptable during breastfeeding