Doxycycline, Tetracycline, Minocycline (PO & IV)


  • Broad spectrum with some Staph & MRSA, Some Gram- & Atypicals
  • Used to treat unusual pathogens: Rickettsia, Lyme Disease, Tularemia, Vibrio, Brucella, Q Fever, Anthrax, Rocky Mountain Fever, Acne, Chlamydial infection, Mycoplasma infection, STD’s
  • Doxycycline is the Tetracycline preferred choice due to the convenient BID dosing & lack of food-drug interactions
  • Doxycycline & Minocycline can be used in patients with renal failure (because it is excreted in bile)
  • Don’t give with products that contain- Ca, Mg, Zn, Fe, & Milk- It will decrease the effectiveness
  • Side Effects: Hepatotoxicity (Liver failure), Photosensitivity, Falconi-like Syndrome (damage to kidneys from taking outdated/degraded Tetracycline), Intracranial HTN with severe headache & blurred vision, decreases effectiveness of oral contraceptives, Discoloration of teeth and decrease bone growth in children
  • Contraindicated in children and pregnant/nursing women
  • Renally impaired patients should not use tetracyclines, except doxycycline


Lyme Disease

  • Caused by Borrelia burgdorferi
  • infection results in skin lesions, headache, and fever, followed by meningoencephalitis and eventually arthritis
  • A single 200mg dose of doxycycline given within 72 hours after a tick bite can prevent development of the disease

Mycoplasma Pneumoniae

  • A common cause of community acquired pneumonia in young adults & people who live in close confines
  • Treatment with doxycycline leads to shorter duration of fever, cough, and malaise
  • Treatment with macrocodes is also effective


  • caused by Vibrio cholera 
  • Ingested in fecally contaminated food or water
  • The organism multiplies in the GI tract where it recreates an enterotoxin that causes diarrhea
  • Treatment includes fluid replacement & doxycycline which reduces the number of intestinal vibrios 

Chlamydial Infections

  • Chlamydia trachomatis is the major cause of sexually transmitted disease in the United States
  • It causes nongonococcal urethritis, pelvic inflammatory disease, & lymphogranuloma venereum
  • Doxycycline or azithromycin is used to treat chlamydial infections

Rocky Mountain Spotted Fever

  • caused by Rickettsia rickettsii
  • Characterized by fever, chills, and aches in bones and joints
  • Response to tetracyclines is prompt if the drug is started early in the disease process


Side Effects

  • Hepatotoxicity (Liver failure)
  • Photosensitivity
  • Falconi-like Syndrome (damage to kidneys from taking outdated/degraded Tetracycline)
  • Intracranial HTN with severe headache & blurred vision
  • ↓ effectiveness of oral contraceptives
  • Discoloration of teeth and decrease bone growth in children



Key Notes

The use of Tetracycline is contraindicated in children younger than age 8 because of permanent staining of the teeth


Doxycycline can be administered safely with milk or an antacid, but the other Tetracyclines cannot


If a patient is taking Minocycline, a sudden change in mental status may indicate intracranial hypertension