What is doxycycline used for?

Doxycycline treats a wide variety of bacterial infections. It will not work against viral infections such as the common cold and flu. 

• Doxycycline is used for the treatment of:
  • Respiratory tract infections
  • Urinary tract infections
  • Eye infections
  • Sexually-transmitted infections:
    • Chlamydia
    • Gonorrhea
    • Syphilis
  • Rickettsial infections - these infections are spread by ticks, mites, fleas, or licelice
    • Rocky Mountain spotted fever
    • Typhus fever
    • Q fever
    • Rickettsialpox
    • Tick fevers
  • Intestinal infections - doxycycline is used in combination with other medications
  • Severe acne - doxycycline is used in combination with other medications
• Post-exposure to anthrax - doxycycline reduces the progression of disease following exposure through inhalation of Bacillus anthracis
• Prevention of malaria

How does doxycycline work?

Doxycycline hyclate belongs to the drug class known as tetracycline antibiotics; they bind to the ribosomal subunit (an enzyme) of the bacteria, preventing its amino acids from forming. Bacteria are not able to function without proteins made by the ribosomal subunit.

Doxycycline is bacteriostatic, meaning it stops bacteria (hence "bacterio-") from reproducing then spreading (hence "static"); It does not necessarily kill them. 

Doxycycline is effective against gram-negative, gram-positive, anaerobic, and other bacteria.

What is the suggested dosing for doxycycline?

This medication guide provides the dosing information for doxycycline oral capsule, tablet, syrup, suspension, and doxycycline delayed-release oral capsule.

Typical dosing for doxycycline hyclate immediate-release oral capsule, tablet, syrup, and suspension:

Infection treatment:

• Adults: take 100 mg by mouth every 12 hours on the first day
  • Then take 100 mg by mouth once daily or 50 to 100 mg every 12 hours.
• Children 8 years or older weighing 45 kg or more: take 100 mg by mouth every 12 hours on the first day
  • Then take 100 mg by mouth once daily or 50 to 100 mg every 12 hours.
• Children 8 years or older weighing less than 45 kg: 
  • Doses are weight-based; determined by the doctor 
  • Usual dose: 
    • 4.4 mg per kg of body weight per day, divided into 2 doses on the first day of treatment 
    • Followed by 2.2 mg per kg of body weight per day, taken as a single dose or divided into 2 doses on the following days
• Children younger than 8 years: use and dose must be determined by the pediatrician

Malaria prevention:

• Adults: take 100 mg by mouth once daily; take the first dose 1 or 2 days before traveling to an area where malaria infection may occur. Continue taking it every day throughout the trip and for 4 weeks after leaving the area of potential malaria infection.
• Children 8 years or older weighing 45 kg or more: take 100 mg by mouth once daily
  • Take the first dose 1 or 2 days before traveling to an area where malaria infection may occur.
  • Continue taking it every day throughout the trip and for 4 weeks after leaving the area of potential malaria infection.
• Children 8 years or older weighing less than 45 kg: 
  • Doses are weight-based; determined by the doctor 
  • Usual dose: 
    • 2 mg per kg of body weight, taken as a single dose 
    • Take the first dose 1 or 2 days before traveling to an area where malaria infection may occur. 
    • Continue taking it every day throughout the trip and for 4 weeks after leaving the area or potential malaria infection.
• Children younger than 8 years: Use is not recommended

Possible anthrax exposure:

• Adults and children weighing 45 kg or more: take 100 mg by mouth every 12 hours for 60 days 
• Children weighing less than 45 kg:
  • Doses are weight-based; determined by the doctor 
  • Usual dose: 2.2 mg per kg of body weight per day, divided into two doses taken every 12 hours for 60 days

Typical dosing for doxycycline delayed-release oral capsule (40 mg):

• Treatment of pimples from rosacea:
  • Adults: take 40 mg (one capsule) once daily in the morning
  • Children: use and dose must be determined by the pediatrician