Doxycycline

A broad-spectrum tetracycline antibiotic used for bacterial and atypical infections.

What is Doxycycline?

Doxycycline is a tetracycline-class antibiotic effective against Gram-positive, Gram-negative, and atypical organisms.

It is widely used due to its good oral absorption and long half-life.

History & Background

Doxycycline was developed as a second-generation tetracycline with improved absorption and fewer renal side effects.

Chemical Structure & Properties

• IUPAC name: (4S,4aR,5S,5aR,6R,12aS)-4-(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,5,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide
• Molecular formula: C₂₂H₂₄N₂O₈
• Molar mass: 444.43 g/mol
• Functional groups: Amide, phenolic OH, tertiary amine

Mechanism of Action

Doxycycline inhibits bacterial protein synthesis by:

• Binding to the 30S ribosomal subunit
• Blocking attachment of aminoacyl-tRNA
• Preventing bacterial growth (bacteriostatic)

Pharmacokinetics

• Absorption: Excellent oral absorption
• Peak plasma time: 2–3 hours
• Half-life: 16–22 hours
• Metabolism: Minimal
• Excretion: Feces and urine

Medical Uses

• Acne vulgaris
• Respiratory tract infections
• Sexually transmitted infections
• Malaria prophylaxis
• Rickettsial infections

Dosage Guidelines

Adults: 100 mg once or twice daily

Malaria prophylaxis: 100 mg daily

⚠️ Take with plenty of water; avoid lying down immediately.

Side Effects

• Nausea
• Photosensitivity
• Esophagitis
• Diarrhea

Warnings & Precautions

• Avoid excessive sunlight
• Not recommended in pregnancy
• Not for children under 8 years

Drug Interactions

• Antacids and iron supplements
• Oral contraceptives
• Isotretinoin

Frequently Asked Questions

Is doxycycline strong? – Yes.

Can it treat viral infections? – No.

Does it cause sunburn? – Yes, photosensitivity.

Can it be taken long-term? – Only under supervision.

⚠️ Educational content only. Not a substitute for professional medical advice.