💊 Oxytetracycline is a broad-spectrum tetracycline antibiotic used primarily for acne vulgaris and rosacea.
It works by inhibiting bacterial protein synthesis and has both antimicrobial and anti-inflammatory effects on the pilosebaceous unit.
It is best taken on an empty stomach, away from milk or antacids, to optimise absorption.
📘 About
- Always check the BNF entry here for full prescribing details and renal-dose adjustments.
- Commonly used in dermatology for chronic inflammatory acne and rosacea.
- Older tetracycline, but still cost-effective and well tolerated if used appropriately.
⚙️ Mode of Action
- Reversibly binds to the 30S ribosomal subunit of susceptible bacteria.
- Prevents attachment of aminoacyl-tRNA to the ribosome → inhibits protein synthesis.
- Bacteriostatic rather than bactericidal, with broad Gram-positive and Gram-negative activity.
- In acne, reduces Cutibacterium acnes colonisation and local inflammation in follicles.
💊 Indications & Dose
- Acne vulgaris, rosacea: 250–500 mg PO every 6 hours, usually for 6–12 weeks.
- Swallow whole with plenty of water; avoid immediately before lying down (oesophageal irritation).
- Take 1 hour before or 2 hours after food, milk, or antacids.
🔄 Interactions
- Absorption reduced by dairy products, iron, calcium, aluminium or zinc (chelates with divalent cations).
- May reduce efficacy of oral contraceptives if vomiting or diarrhoea occur.
- See BNF for comprehensive list.
⚠️ Cautions
- Avoid concurrent dairy intake — impairs absorption via chelation.
- Use cautiously in myasthenia gravis (may worsen weakness).
- Photosensitivity: advise patients to use sun protection.
- Ensure adequate hydration to reduce risk of oesophagitis.
🚫 Contraindications
- Pregnancy and breastfeeding: crosses placenta and deposits in fetal bone/teeth.
- Children < 12 years: causes permanent tooth discoloration and enamel hypoplasia.
- Severe renal or hepatic impairment: accumulation and toxicity risk.
💥 Adverse Effects
- Gastrointestinal upset (nausea, dyspepsia, diarrhoea).
- Photosensitivity reactions and rash.
- Oesophageal irritation or ulceration (especially if taken before bed).
- Rare: hepatotoxicity, intracranial hypertension, superinfection (Candida).
🧠 Teaching Note
Tetracyclines are classic examples of drugs forming insoluble chelates with calcium.
For dermatology trainees, note that newer tetracyclines (e.g. doxycycline, lymecycline) are preferred for adherence, but oxytetracycline remains a valid and inexpensive first-line choice in UK primary care.
📚 References
🕓 Revisions
- 2025-10 — Content expanded and annotated by Dr O’Kane (Makindo edition).
