Makindo Medical Notes

💊 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

• BNF: Oxytetracycline
• NICE CKS: Acne vulgaris (2024)
• DermNet NZ: Tetracyclines

🕓 Revisions

• 2025-10 — Content expanded and annotated by Dr O’Kane (Makindo edition).