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Antibiotic (Tetracycline) Pregnancy: D — contraindicated

Doxycycline

Brand names: Vibramycin, Efracea (low-dose)

Adult dose

Dose: 100mg twice daily on day 1, then 100mg once daily
Route: Oral
Frequency: Once or twice daily
Most infections: 200mg loading dose then 100mg OD. Chlamydia: 100mg BD × 7 days. Malaria prophylaxis: 100mg OD starting 1 day before travel.

Clinical pearls

  • Take upright with full glass of water, do not lie down for 30 min — prevents oesophageal ulceration
  • Alternative to amoxicillin in penicillin-allergic patients for CAP
  • First-line for atypical organisms: Chlamydia, Mycoplasma, Rickettsia, Lyme disease
  • Advise sunscreen — significant photosensitivity during treatment
  • NOT for children <12 years or pregnancy — tetracyclines bind calcium in developing bone/teeth

Contraindications

  • Children <12 years (dental staining)
  • Pregnancy
  • Oesophageal stricture
  • Systemic lupus (relative)

Side effects

  • Photosensitivity
  • Oesophageal irritation/ulceration
  • GI upset
  • Hepatotoxicity (high doses)
  • Benign intracranial hypertension

Interactions

  • Antacids, iron, dairy — reduce absorption (take 2h apart)
  • Warfarin — increased INR
  • Oral contraceptives — theoretical

Monitoring

  • Photosensitivity symptoms
  • LFTs (prolonged high-dose use)

Reference: PHE Antibiotic Guidelines; BASHH Chlamydia Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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