Minocycline, DoxycyclineMechanism of action, pharmacological properties, dosage, side effects

👁 Tetracycline Antibiotics in Ophthalmology – From Topical to Oral Therapy

Tetracyclines are broad-spectrum antibiotics that inhibit bacterial protein synthesis.
In ophthalmology, they are used as both topical eye ointments and oral medications depending on the indication.

 

 

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✅ Common Forms in Ophthalmic Use

1. Topical – Terramycin (Oxytetracycline)

• Historically used for post-surgical care and blepharitis
• Effective against Gram-positive skin flora
• Now less favored due to newer fluoroquinolone-based ointments

2. Oral – Minocycline & Doxycycline

• Useful in meibomian gland dysfunction and chronic blepharitis
• Dosage:
  • Minocycline: 100mg BID
  • Doxycycline: Less preferred due to absorption and GI issues

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✅ Comparison of Minocycline vs Doxycycline

FeatureMinocyclineDoxycycline

Half-life	~12 hrs	~12–16 hrs
Food interaction	Less affected	Requires fasting
Side effects	Mild	More GI/renal issues
Preferred use	1st line in ophthalmology	Alternative

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✅ Safety Precautions

• Avoid in children and pregnant women (skeletal/teeth risks)
• Photosensitivity: Avoid sun exposure during use
• Never take expired pills – may cause renal toxicity
• Take with full glass of water to prevent esophageal injury