Doxycycline is a Tetracycline-Class Antibiotic
Doxycycline is a synthetic tetracycline-class antibiotic that exerts its antimicrobial effect primarily through inhibition of bacterial protein synthesis. 1
Mechanism of Action
Doxycycline, like other tetracyclines, works by:
- Binding to the 30S subunit of the bacterial ribosome 2
- Inhibiting protein synthesis in susceptible bacteria 1
- Acting primarily as a bacteriostatic agent 3
- Demonstrating anti-inflammatory properties in addition to its antimicrobial effects 4
Pharmacological Properties
Doxycycline has several advantageous pharmacological properties:
- High degree of lipoid solubility 1
- Low affinity for calcium binding 1
- High stability in normal human serum 1
- Virtually complete oral absorption 1
- Long half-life (18-22 hours) allowing for convenient twice-daily dosing 3
- Well absorbed even in the presence of food 3
- Excellent tissue penetration 3
- No dose adjustment required in renal insufficiency 3
Clinical Applications
Doxycycline is commonly used in:
Dermatology
- Treatment of moderate to severe inflammatory acne (50-100mg twice daily) 5
- Management of rosacea 2
- Often used at lower doses for its anti-inflammatory properties rather than antimicrobial effects 4
Infectious Diseases
- Effective against a wide range of gram-positive and gram-negative organisms 1
- Treatment of atypical pneumonias 3
- Management of sexually transmitted diseases 3
- Treatment of rickettsial infections 3
- First-line treatment for bubonic plague 2
- Treatment of Lyme disease 3
Ophthalmology
- Management of blepharitis and meibomian gland dysfunction 2
Adverse Effects
Common adverse effects include:
- Gastrointestinal disturbances (15.7% vs 5.9% with placebo) 2
- Photosensitivity (more common with doxycycline than minocycline) 2
- Esophagitis, especially when taken with insufficient water or before lying down 6
- Rare but serious: intracranial hypertension 2
- Rarely: acute pancreatitis 7
Contraindications and Precautions
Doxycycline is contraindicated in:
- Children under 8 years of age due to risk of teeth staining 2, 5
- Pregnant or breastfeeding women 2, 5
- Patients with hypersensitivity to tetracyclines 2
Practical Administration Tips
To minimize adverse effects:
- Take doxycycline with food and adequate fluids 2
- Remain upright after taking the medication to prevent esophagitis 2, 6
- Avoid sun exposure due to increased risk of photosensitivity 2
- Consider drug interactions, particularly with oral contraceptives and warfarin 2
Doxycycline remains a versatile antibiotic with broad applications across multiple medical specialties due to its favorable pharmacokinetic profile and dual antimicrobial and anti-inflammatory properties.