Doxycycline
Vibramycin | Doryx | Oracea
Overview
Doxycycline is a broad-spectrum tetracycline antibiotic used to treat respiratory, skin, genital, and tick-borne infections, and as prophylaxis for malaria.
Indications
- Community-acquired pneumonia
- Acne
- Chlamydial and other STIs
- Tick-borne illnesses such as Lyme disease and Rocky Mountain spotted fever
- Malaria prophylaxis
Contraindications
- Hypersensitivity to tetracyclines
- Pregnancy
- Children under 8 years (except specific indications)
Classification
Mechanism of Action
Reversibly binds to the 30S bacterial ribosomal subunit, blocking attachment of aminoacyl-tRNA and inhibiting bacterial protein synthesis; it is bacteriostatic.
Pharmacodynamics
Active against many gram-positive and gram-negative bacteria as well as atypical organisms such as Chlamydia, Mycoplasma, and Rickettsia.
Pharmacokinetics
- Absorption
- Almost completely absorbed orally; absorption reduced by divalent and trivalent cations.
- Distribution
- Lipophilic with wide tissue distribution and high protein binding.
- Metabolism
- Not extensively metabolized.
- Excretion
- Excreted in feces and urine; partially eliminated via the gut, so dose adjustment is usually not required in renal impairment.
- Half-life
- Approximately 18-22 hours
- Bioavailability
- Approximately 90-100%
- Protein Binding
- Approximately 80-90%
Dosage
Typical dosage: 100 mg once or twice daily
Available Forms
- Tablet
- Capsule
- Delayed-release capsule
- Oral suspension
- Injection
Side Effects
Common
- Nausea
- Photosensitivity
- Esophageal irritation
- Diarrhea
Serious
- Clostridioides difficile colitis
- Intracranial hypertension
Rare
- Hepatotoxicity
- Severe skin reactions
Drug Interactions
Calcium, magnesium, aluminum, iron, and zinc chelate doxycycline and markedly reduce its absorption.
May enhance anticoagulant effect and raise INR.
Warnings
Pregnancy
Category D
Toxicity
Excessive use can cause hepatotoxicity; tetracyclines deposit in developing teeth and bone.
Overdose
Provide supportive care; discontinue the drug. Antacids or magnesium salts may reduce further absorption.
References
Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.