Emergency Use of Doxycycline

What to know

In an anthrax emergency, you could be exposed to the bacteria that cause anthrax. Taking the prescription antibiotic doxycycline (DOX-i-SYE-kleen) helps reduce the risk of illness and death if you've been exposed.

A bottle of medicine on a countertop

About doxycycline

Doxycycline is a prescription antibiotic approved by the Food and Drug Administration (FDA) to prevent anthrax.

Anthrax is a serious disease that you can get if you come in contact with infected animals or animal products. You can also get anthrax if you're exposed to it during a bioterrorism event. You can get sick if you breathe in anthrax spores, eat or drink contaminated products, or if the bacteria that causes anthrax enter the skin through a wound or sore. Anthrax is not contagious, so you can't get it from another person who has anthrax.

Keep Reading: About Anthrax

Information on this page can also be found on a printable factsheet.

During an emergency

In an anthrax emergency, you will receive doxycycline to protect you from potential exposure to anthrax bacteria. Public health authorities will provide guidance on who should get the medication.

Start taking the medicine as soon as possible after the emergency until you get guidance from public health officials or your healthcare provider to stop taking it. This guidance will likely be based on how likely it was that you were exposed to anthrax.

If you were told you were potentially exposed to anthrax, take the medicine two times each day, 12 hours apart. To reduce your chance of getting sick, take the medicine as long as you are directed and do not stop taking it early. Most people will be given a 10-day supply to start, but you may have to take it for up to 60 days. Public health officials will tell you whether you need more and how to get it.

Tell your doctor if you are pregnant, become pregnant, or are breastfeeding while you're taking doxycycline.

Allergic reactions to doxycycline‎

Do not take doxycycline if you've experienced a severe allergic reaction to it or other tetracycline medications. A severe reaction may include closing of the throat; trouble breathing; swelling of the lips, tongue, or face; or confusion.

Based on its scientific review, the FDA allows using certain lots of doxycycline even after the expiration date. For more information, go to the FDA website.

Instructions for use

  • Take the medication for as long as it's directed, and don't skip doses. Do not take 2 doses at once if you miss one. Take the next dose when it's scheduled.
  • Doxycycline works just as well whether you take it with or without food or milk. Take it with food if you get an upset stomach when you take the medicine.
  • Keep the pills dry. Store doxycycline pills and liquid at 68 to 77°F (20 to 25°C).

Adults and children 76 pounds (35kg) or more

  • Take 1 pill (100 mg) in the morning with a full glass of water.
  • Twelve (12) hours later, take 1 pill (100 mg) in the evening with a full glass of water.

Children under 76 pounds (35kg)

  • Follow instructions provided on the liquid doxycycline label.
  • Take the same amount in the morning and evening (12 hours apart) each day for as long as healthcare providers or officials recommend you should take it.
  • Follow the directions for crushing and mixing if your child is prescribed a tablet but can't swallow a pill.

Hotline information‎

Call the poison control center at 1-800-222-1222 if children or pets eat the medicine by accident.

Taking with other medicines

Talk to your doctor if you are on a blood thinner like warfarin or seizure medicine like phenytoin. Taking doxycycline may affect how much of these medicines you need to take.

Doxycycline can make birth control pills less effective. Use a second form of birth control until you finish taking all of your doxycycline.

Doxycycline might not work as well if you take it when you're on some other medicines. Take doxycycline at least 2 hours before or 2 hours after taking:

  • Multivitamins, supplements or antacids with aluminum, calcium, iron, or magnesium
  • Helidac, Kaopectate, Pepto-Bismol or other products with bismuth subsalicylate used for indigestion, nausea, or diarrhea

Side effects

Although there are potential side effects, the benefits of using doxycycline to prevent disease and death from anthrax exposure outweigh the risks.

Common side effects

Doxycycline can cause your skin to be more sensitive to the sun. Use sunscreen and cover exposed skin. Keep taking doxycycline even if you have some of the following side effects:

  • Mild nausea
  • Vomiting and/or diarrhea
  • Mild sunburn
  • Vaginal yeast infection

Serious side effects

Serious side effects from doxycycline are rare. They include:

  • Closing of the throat or trouble breathing
  • Swelling of the lips, tongue, or face
  • Severe itching or rash, especially hives and wheals (red, swollen bumps on the skin)
  • Severe stomach cramps with fever or bloody or watery diarrhea
  • Yellowing of the eyes or skin, or dark brown or tea-colored urine (jaundice)
  • Pain when swallowing (esophageal ulcers)
  • Unusual bleeding or bruising
  • Severe headaches, dizziness, or double vision

You should stop taking doxycycline and talk to your doctor right away if you experience these symptoms.

Long term side effects

  • Doxycycline can slow bone growth in children.
  • Doxycycline can lead to discolored teeth or poor tooth enamel in children under 8 years.
    • This risk is also for infants whose mothers took doxycycline during the last half of pregnancy or while nursing.

Alternatives to doxycycline

Public health officials will tell you if other antibiotics (such as ciprofloxacin, levofloxacin, or amoxicillin) are available. Talk to public health officials or healthcare providers if you cannot take doxycycline.

Medical compensation

In the rare event that doxycycline causes serious problems, you may be eligible to receive help with medical costs. A federal program may help cover medical costs for those seriously affected by certain medicines or vaccines. Learn more about the Countermeasures Injury Compensation Program (CICP) at hrsa.gov/cicp or by calling 1-855-266-2427 (toll-free).