Pediatric Resident

Drug Name: Doxycycline

Click on the titles below for drug details

  • Diffuses into bacterial cells, binds the 30s ribosomal subunit, and inhibits bacterial protein synthesis
  • Can also cause alterations in the cytoplasmic membrane of bacterial cells.
  • Bacteriostatic
  • Can be adminisntered IV or orally (tablet and suspension)
    • IV formulation requires high volumes and often causes discomfort (burning sensation). With intact GI function, consider PO when possible, given excellent bioavailability with enteral administration.
    • Recommended to be taken with food.
    • Avoid taking doxycycline with foods that contain aluminum, calcium, iron, or other divalent cations, as they can bind to doxycycline and decrease its absorption.
  • Concentrates in bile and is excreted in both urine and stool. No renal or hepatic dosage adjusments are recommended.
  • Starting doses:
    • 2.2mg/kg/dose every 12 hours, max dose 100mg/dose.
    • Pneumonia (CAP and atypical): 1-2mg/kg/dose BID for 10 days
      • While sometimes used for suspected MRSA pneumonia, Doxycycline is not a perfect choice for CAP given growing resistance of Strep pneumoniae to tetracyclines.
    • Lyme disease: 2.2mg/kg/dose BID (max 100 mg/dose); variable duration based on symptoms.
      • The AAP has recently started recommending doxycycline even for young children with Lyme Disease (as opposed to amoxicillin) given low risk of teeth staining with short durations. The exception is Lyme arthritis, where children <8 years old will still often be prescribed amoxicillin.
    • Acne vulgaris: 50mg-100 mg once or twice daily OR 150 mg once daily.
  • Very broad spectrum of activity that includes bacteria and some protozoa.
  • Specifically has great coverage against:
    • Gram Positives: S. aureus (MSSA and MRSA); Enterococcus (including some vancomycin-resistant strains), and Bacillus anthracis.
      • Of note, there is significant growing resistance of Group A Streptococcus to tetracyclines (upwards of 50% in recent years). This is a reason to pause before prescribing doxycycline for non-suppurative skin- and soft-tissue infections, as the leading organisms would be MSSA or GAS.
    • Gram negatives: H. influenzae, E. coli, Klebsiella, Enterobacter, Serratia, and Neisseria (Covers some AmpC-producing bacteria!).
    • First-line agent for Lyme Disease, including for erythema migrans, mild Lyme carditis, mild Lyme meningitis (may consider IV ceftriaxone to start regimen for patients with significant neurologic symptoms), and arthritis.
    • Intracellular/atypical bacteria like Mycoplasma, Chlamydia, and Legionella.
    • DOES cover against some species of Plasmodium.
    • Does NOT cover anaerobic bacteria very well.
  • Contraindicated in the following populations:
    • Patients with allergic reactions to tetracycline antibiotics.
    • Patients with Myasthenia Gravis (can increase muscle weakness).
    • Patients actively taking oral isotretioin (increased risk for idiopathic intracranial hypertension).
  • Can cause hepatotoxicity, interstitial nephritis, bronchospasm, and neurologic symptoms such as dizziness, vertigo, and tinnitus.
  • Nausea, vomiting, dyspepsia, especially when taken on an empty stomach.
  • Discomfort with IV infusions.
  • Allergic reactions are rare but possible, including anaphylaxis, serum sickness, and Stevens-Johnson Syndrome.
  • Oral doxycycline has nearly 100% bioavailability
  • Has some CNS peentration - surprasses MIC for Borrelia burgdorferi, so is recommended treatment for Lyme meningitis/encephalitis.
    • However, not recommended for other causes of meningits as it may not accumulate in the CSF at high enough concentrations to be effective.
  • Poor penetration into bone.
  • No specific data on penetration/accumulation in lung tissue, but does have clinical evidence of efficacy against pulmonary infections.
  • Tooth staining - often not utilized in young children because of this. However, more recent data showed that short courses of doxycycline, unlike tetraycyline or minocycline, have very minimal risk of staining.
  • Pill esophagitis if taken in tablet form - recommend taking with large glass of water and sitting upright to minimize risk of esophageal irritation.
  • Should be taken with food to reduce GI upset, but separately from foods/drinks high in calcium (e.g., milk, yogurt, cheese), as calcium can chelate doxycycline and decrease its absorption.
  • Phototoxicity is a well-known and common side effect. There is an increased risk for sunburn if exposed to UV light. Use extra caution and avoid UV light when possible. Recommend that if a patient is outside while on doxycycline that they should use sunscreen or wear protective clothing.
    • Especially important in adolescent patients who may use topical retinol creams as part of their skin care regimen, as they already have an increased risk of photosensitivity.