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Am Fam Physician. 2001;64(11):1901-1903

The Centers for Disease Control and Prevention (CDC) has issued an update on the investigation of recent cases of anthrax exposure. This update includes the susceptibility patterns of Bacillus anthracis isolates, and provides interim recommendations for managing potential threats and exposures and for treating anthrax. The complete report appears in the October 26, 2001 issue of Morbidity and Mortality Weekly Report and is available on the CDC Web site atwww.cdc.gov/mmwr. A copy of the report is also available on the Web site of the American Academy of Family Physicians atwww.aafp.org/resources.

Managing Exposure

The highest priority is to identify at-risk persons and initiate appropriate interventions to protect them. The exposure circumstances are the most important factors that direct decisions about prophylaxis. Persons with an exposure or contact with an environment known, or suspected, to be contaminated with B. anthracis—regardless of laboratory test results—should be offered antimicrobial prophylaxis. Exposure or contact, not laboratory results, is the basis for initiating treatment.

Antimicrobial Treatment

A high index of suspicion and rapid administration of effective antimicrobial therapy is essential for prompt diagnosis and effective treatment of anthrax. Limited clinical experience is available and no controlled trials in humans have been performed to validate current treatment recommendations for inhalational anthrax. Based on studies in nonhuman primates and other animals and in vitro data, ciprofloxacin or doxycycline should be used for initial intravenous therapy until antimicrobial susceptibility results are known (Table 1).

Two or more antimicrobial agents predicted to be effective are recommended because of the mortality associated with inhalational anthrax. Other agents with in vitro activity suggested for use in conjunction with ciprofloxacin or doxycycline include rifampin, vancomycin, imipenem, chloramphenicol, penicillin and ampicillin, clindamycin and clarithromycin, but other than for penicillin, limited or no data exist about using these agents in the treatment of inhalational B. anthracis infection. Cephalosporins and trimethoprim-sulfamethoxazole should not be used for therapy, and penicillin G and ampicillin alone should not be used to treat systemic infection because the combination may not be clinically effective for inhalational anthrax where large numbers of organisms are likely to be present.

Toxin-mediated morbidity is a major complication of systemic anthrax. Corticosteroids have been suggested as adjunct therapy for inhalational anthrax associated with extensive edema, respiratory compromise, and meningitis.

For cutaneous anthrax, ciprofloxacin and doxycycline are first-line therapy (Table 2). Intravenous therapy with a multidrug regimen is recommended if signs of systemic involvement, extensive edema, or lesions on the head and neck are present. Antimicrobial treatment may render lesions culture negative in 24 hours, but progression to eschar formation still occurs. Typically, cutaneous anthrax is treated for seven to 10 days, but with the latest attacks, the risk for simultaneous aerosol exposure appears to be high. Although infection may produce an effective immune response, a potential for reactivation of latent infection may exist, so patients should be treated for 60 days.

CategoryInitial therapy (IV)§Duration
AdultsCiprofloxacin, 400 mg every 12 hours*
or
Doxycycline, 100 mg every 12 hours¶
and
One or two additional antimicrobials§
IV treatment initially∥; switch to oral antimicrobial therapy when clinically appropriate:
Ciprofloxacin, 500 mg orally twice daily
or
Doxycycline, 100 mg orally twice daily
Continue for 60 days (IV and oral combined).#
ChildrenCiprofloxacin, 10 to 15 mg per kg every 12 hours**††
or
Doxycycline‡‡¶: >8 years and >45 kg: 100 mg every 12 hours; >8 years and ≤45 kg: 2.2 mg per kg every 12 hours; ≤8 years: 2.2 mg per kg every 12 hours;
and
One or two additional antimicrobials§
IV treatment initially∥; switch to oral antimicrobial therapy when clinically appropriate:
Ciprofloxacin, 10 to 15 mg per kg orally every 12 hours††or
Doxycycline‡‡: >8 years and >45 kg: 100 mg orally twice daily; >8 years and ≤45 kg: 2.2 mg per kg orally twice daily; ≤8 years: 2.2 mg per kg orally twice daily
Continue for 60 days (IV and oral combined).#
Pregnant women§§Same for nonpregnant adults (the high death rate from infection outweighs the risk posed by the antimicrobial agent)IV treatment initially; switch to oral antimicrobial therapy when clinically appropriate†: oral therapy regimens are same for nonpregnant adults.
Immunocompromised personsSame for nonimmunocompromised persons and childrenSame for nonimmunocompromised persons and children

All medications may have side effects and allergic reactions. Physicians should be aware of these side effects and consult an infectious diseases specialist as needed. Patients should be urged to inform their health care provider of any adverse events.

CategoryInitial therapy (oral)Duration
Adults*Ciprofloxacin, 500 mg twice daily60 days‡
or
Doxycycline, 100 mg twice daily
Children*Ciprofloxacin, 10 to 15 mg per kg every 12 hours (not to exceed 1 g per day)†60 days‡
or
Doxycycline§: >8 years and >45 kg: 100 mg every 12 hours; >8 years and <=45 kg: 2.2 mg per kg every 12 hours; <=8 years: 2.2 mg per kg every 12 hours
Pregnant women*∥Ciprofloxacin, 500 mg twice daily60 days‡
or
Doxycycline, 100 mg twice daily
Immunocompromised persons*Same for nonimmunocompromised persons and children60 days‡

Coverage of guidelines from other organizations does not imply endorsement by AFP or the AAFP.

This series is coordinated by Michael J. Arnold, MD, contributing editor.

A collection of Practice Guidelines published in AFP is available at https://www.aafp.org/afp/practguide.

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Copyright © 2001 by the American Academy of Family Physicians.

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