Anthrax Medication

Updated: Mar 23, 2016
  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Medication

Medication Summary

Before October 2001, the first-line treatment of anthrax infection and prophylaxis was penicillin; however, this is not the case for bioterrorism-related cases because of the concern for genetically engineered penicillin-resistant anthrax strains. The Centers for Disease Control and Prevention (CDC) recommends ciprofloxacin or doxycycline. Doxycycline should not be used in suspected meningitis because it has poor penetration of the central nervous system.

Quinolones are not routinely indicated for pediatric patients because of the risk of musculoskeletal disorders. However, in 2008, the US Food and Drug Administration (FDA) approved use of levofloxacin in children as young as 6 months for the treatment of inhalational (and inhalational exposure to) anthrax. [15] Treatment duration is 60 days, but safety has not been evaluated beyond 14 days.

Women who are pregnant or breastfeeding can use amoxicillin. Resistance exists to third-generation cephalosporins, trimethoprim, and sulfisoxazole. For patients with severe anthrax, therapy with corticosteroids and intravenous antibiotics is recommended.

Individuals with inhalational anthrax should receive a multidrug regimen of either ciprofloxacin or doxycycline along with at least one more agent, including a quinolone, rifampin, tetracycline, vancomycin, imipenem, meropenem, chloramphenicol, clindamycin, or an aminoglycoside. After susceptibility testing and clinical improvement, the regimen may be altered.

Raxibacumab, a monoclonal antibody directed at the protective antigen of Bacillus anthracis, is available from the CDC for treatment of inhalational anthrax in adults and children. It is used as part of a combination regimen with appropriate antibiotic drugs. It is also approved for prophylaxis of inhalational anthrax when alternative therapies are not available or not appropriate. [14]

Human anthrax immune globulin (Anthrasil) is indicated for treatment of inhalational anthrax in adults and children in combination with antibiotic therapy. [9]

Cases of gastrointestinal and cutaneous anthrax can be treated with ciprofloxacin or doxycycline for 60 days. Penicillin such as amoxicillin or amoxicillin-clavulanate may be used to complete the course if the strain is susceptible.

Measures to prevent anthrax infection after exposure include vaccination, decontamination, and prophylactic treatment. For people who have been exposed to anthrax but do not have symptoms, 60 days of ciprofloxacin, a tetracycline (including doxycycline), or penicillin is given to reduce the risk or progression of disease due to inhaled anthrax.

A vaccine (anthrax vaccin adsorbed) is also available. It is indicated for pre-exposure prophylaxis in persons at high risk of exposure and for postexposure prophylaxis following suspected or confirmed B anthracis exposure.

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Antibiotics, Other

Class Summary

Empirical antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Penicillin G (Pfizerpen)

Penicillin interferes with the synthesis of bacterial cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Penicillin is the drug of choice for nonbioterrorism-related anthrax. Treatment should begin with intravenous dosing.

Penicillin VK (Pen Vee K, Penicillin V, Veetids)

Penicillin interferes with the synthesis of bacterial cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Penicillin is the drug of choice for nonbioterrorism-related anthrax. Treatment should begin with intravenous dosing.

Penicillin G procaine

Penicillin reduces the incidence or progression of anthrax following exposure to aerosolized B anthracis. Available safety data for penicillin G procaine best support a duration of therapy of 2 weeks or less. Treatment for inhalational anthrax (postexposure) must be continued for a total of 60 days. Physicians must consider risks and benefits of continuing administration of penicillin G procaine for more than 2 weeks or switching to an effective alternative treatment.

In adults, administer by deep IM injection only into the upper outer quadrant of a buttock. In infants and small children, the midlateral aspect of the thigh may be a better site for administration.

Doxycycline (Adoxa, Doryx, Vibramycin)

Doxycycline is a second-generation tetracycline that is more active than tetracycline against many pathogens and is not hepatotoxic. Its adverse-effect profile and pharmacokinetics are different than those of tetracycline. Doxycycline reduces the incidence or progression of anthrax, including inhalational anthrax (postexposure) following exposure to aerosolized B anthracis.

Doxycycline inhibits protein synthesis and, thus, bacterial growth by binding with 30S and, possibly, 50S ribosomal subunits of susceptible bacteria. Although tetracyclines have an adverse effect on teeth in children younger than 8 years, the delay in bone development is apparently reversible; balancing these risks against the lethality of inhalational anthrax, the US Food and Drug Administration recommends a pediatric dosing regimen for inhalational anthrax (postexposure).

Administer IV therapy only when oral administration is not indicated, and do not give over a prolonged period (may increase the risk of thrombophlebitis and other complications). Switch to oral doxycycline or another antimicrobial drug product as soon as possible to complete a 60-day course of therapy.

Amoxicillin (Moxatag)

Amoxicillin interferes with synthesis of cell wall mucopeptides during active multiplication, resulting in bactericidal activity against susceptible bacteria.

Ampicillin

Ampicillin has bactericidal activity against susceptible organisms. It is an alternative to amoxicillin for patients who are unable to take medication orally.

Ciprofloxacin (Cipro, Proquin XR)

Ciprofloxacin is the drug of choice for anthrax when mutant strains are suspected (as in biological warfare). It is indicated for inhalational anthrax post exposure. Ciprofloxacin inhibits bacterial DNA synthesis and, consequently, growth by inhibiting DNA gyrase in susceptible organisms. It has high resistance potential. Initiate treatment immediately following suspected or confirmed anthrax exposure.

Levofloxacin (Levaquin)

Levofloxacin is a second-generation quinolone that acts by interfering with DNA gyrase in bacterial cells and promoting breakage of DNA strands. It is highly active against gram-negative and gram-positive organisms. It has low resistance potential.

Chloramphenicol

Chloramphenicol binds to 50 S bacterial-ribosomal subunits and inhibits bacterial growth by inhibiting protein synthesis. It is effective against gram-negative and gram-positive bacteria.

Streptomycin

Streptomycin is an aminoglycoside antibiotic recommended when less potentially hazardous therapeutic agents are ineffective or contraindicated.

Tetracycline

Tetracycline treats susceptible infections caused by gram-positive and gram-negative bacteria and infections caused by Mycoplasma, Chlamydia, and Rickettsia species. It inhibits bacterial protein synthesis by binding with 30S and, possibly, 50S ribosomal subunits of susceptible bacteria.

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Corticosteroids

Class Summary

These agents are used for severe edema, meningitis, or swelling in the head and neck region.

Dexamethasone (Baycadron)

This agent is used in various inflammatory diseases. Dexamethasone may decrease inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Prednisone

Prednisone is useful in inflammatory and allergic reactions. It may decrease inflammation by reversing increased capillary permeability and suppressing polymorphonuclear neutrophil (PMN) activity.

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Antidotes, Other

Class Summary

A monoclonal antibody (raxibacumab) and human anthrax immune globulin have been approved by the FDA using the animal efficacy rule for inhalational anthrax. [2, 9]

Anthrax immune globulin (Anthrasil)

Human anthrax immune globulin is indicated to provide passive immunization for inhalational anthrax in combination with appropriate antibacterial drugs for adults and children. Its effectiveness is based solely on efficacy studies conducted in animal models of inhalational anthrax. It does not cross the blood-brain barrier and does not prevent or treatment meningitis associated with anthrax. It is prepared using plasma collected from healthy, screened donors who have been immunized with anthrax vaccine adsorbed (BioThrax).

Raxibacumab

Raxibacumab is a recombinant human IgG1-gamma monoclonal antibody directed at the protective antigen of Bacillus anthracis. It is indicated for treatment of inhalational anthrax in adults and children and used in combination with appropriate antibacterial drugs. It is also indicated for prophylaxis of inhalational anthrax when alternative therapies are not available or are not appropriate.

Obiltoxaximab (Anthim, Anthrax antitoxin)

Monoclonal antibody that binds to the protective antigen of B anthracis and prevents the formation of the anthrax toxin that directly damages cell. It is indicated in adult and pediatric patients for the treatment of inhalational anthrax due to B anthracis in combination with appropriate antibacterial drugs. It is also indicated for prophylaxis of inhalational anthrax when alternative therapies are not available or not appropriate.

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Vaccines

Class Summary

The FDA approved a standard anthrax vaccine designated "anthrax vaccine adsorbed" (AVA), which is a sterile filtrate of cultures of an avirulent strain that elaborates protective antigen. No human controlled trials are available. It is the first vaccine approved utilizing the animal rule by the FDA. The efficacy of this vaccine in inhalation (biowarfare) anthrax is questionable.

 

Anthrax vaccine adsorbed (BioThrax)

The vaccine is prepared from a cell-free filtrate of B anthracis, but contains no dead or live bacteria. The virulent components of Bacillus anthracis include an antiphagocytic polypeptide capsule and 3 proteins, including protective antigen (PA), lethal factor (LF), and edema factor (EF). They are not cytotoxic individually, but the combination of PA with LF or EF forms cytotoxic lethal toxin and edema toxin, respectively. The immune mechanism of AVA is unknown but, theoretically, antibodies to PA may provide protection by neutralizing the activities of these toxins. It is indicated for pre-exposure prophylaxis in persons at high risk of exposure and for postexposure prophylaxis following suspected or confirmed B anthracis exposure.

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