Doxycycline After Anthrax Exposure: How to Take It, Side Effects and Interactions

The essentials

• In an anthrax emergency, you could be exposed to the bacteria that cause the disease.
• The prescription antibiotic doxycycline lowers the risk of illness and death if you have been, or may be, exposed.
• Public health officials will tell you what to do if this happens.
• If you take it, follow the directions that come with it.

A bottle of doxycycline tablets. Image from CDC's page.

Anthrax and doxycycline

Anthrax is a serious disease caught from infected animals or animal products — or through a bioterrorism attack. People fall ill by breathing in spores, eating or drinking contaminated products, or when the bacteria enter the skin through a wound or sore. It is not contagious: it does not pass from person to person.

Doxycycline (DOX-i-SYE-kleen) is a prescription antibiotic approved by the FDA to prevent anthrax. CDC also has a printable fact sheet.

When and how long to take it

• If you may be exposed: in an emergency, public health authorities decide who should take doxycycline, usually based on how likely exposure was. If you are told you are at risk, start as soon as possible and keep going until officials or your provider tell you to stop.
• If you have been exposed: take it twice a day, 12 hours apart, for as long as directed — do not stop early. Most people get a 10-day supply to start, but you may need it for up to 60 days; officials will say whether you need more and how to get it.
• Tell your doctor if you are pregnant, become pregnant, or are breastfeeding while taking it.
• Do not take it if you have had a severe allergic reaction to doxycycline or another tetracycline medicine — closing of the throat, trouble breathing, swelling of the lips, tongue or face, or confusion.

For clinicians and public health authorities: after its scientific review, the FDA allows certain lots of doxycycline to be used past their expiration date — see the FDA's page.

How to take it

• Take it for as long as directed, and don't skip doses. If you miss one, do not double up — take the next dose on schedule.
• It works as well with or without food or milk; take it with food if it upsets your stomach.
• Anyone who cannot swallow pills can follow CDC's crushing and mixing directions.
• Keep the pills dry, and store pills and liquid at 68 to 77°F (20 to 25°C).

If a child or pet swallows the medicine by accident, call poison control at 1-800-222-1222.

Other medicines

• On a blood thinner such as warfarin, or a seizure medicine such as phenytoin? Talk to your doctor — doxycycline may change how much of them you need.
• It can make birth control pills less effective: use a second method until you finish the course.
• Take it at least 2 hours before or after:
• • multivitamins, supplements or antacids containing aluminum, calcium, iron or magnesium;
  • bismuth subsalicylate products for indigestion, nausea or diarrhea, such as Pepto-Bismol, Kaopectate or Helidac.

Side effects

In an anthrax exposure, the benefits outweigh the risks.

Common — keep taking it:

• mild nausea, vomiting or diarrhea;
• sun sensitivity and mild sunburn — use sunscreen and cover up;
• a vaginal yeast infection.

Serious, but rare — stop and call your doctor right away:

• closing of the throat or trouble breathing; swelling of the lips, tongue or face;
• severe itching or rash, especially hives and welts;
• severe stomach cramps with fever, or bloody or watery diarrhea;
• yellow 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.

Long-term, in children taking it more than 21 days — though in an anthrax emergency a provider may judge the benefits greater:

• slowed bone growth;
• discolored teeth or weak enamel in children under 8, or in infants whose mothers took doxycycline during the second half of pregnancy or while nursing.

If you can't take it

Officials will say whether other antibiotics — such as ciprofloxacin, levofloxacin or amoxicillin — are available. Talk to them or your provider if you cannot take doxycycline.

Help with medical costs

If doxycycline causes serious problems, which is rare, the federal Countermeasures Injury Compensation Program may help with medical costs for people badly affected by certain medicines or vaccines: 1-855-266-2427.

Sources

Based on "Emergency Use of Doxycycline," Anthrax, Centers for Disease Control and Prevention; a work of the United States government in the public domain.