TABLE 11. Empiric* treatment regimens for pregnant or lactating persons aged ≥18 years^†,§ with systemic^¶ anthrax with or without meningitis, by descending order of preference — CDC recommendations, 2023.

Regimen		Example
Regimen 1. Two bactericidal drugs from different antimicrobial drug classes plus a PSI or an RNAI		Ciprofloxacin plus meropenem plus doxycycline or omadacycline**
Regimen 2. One bactericidal drug plus a PSI		Meropenem plus linezolid or doxycycline
Regimen 3. One bactericidal drug plus a second bactericidal drug from a different antimicrobial drug class		Meropenem plus ciprofloxacin
Regimen 4. One bactericidal drug plus an RNAI (rifampin should not be used as monotherapy)		Meropenem plus rifampin
Regimen 5. A PSI plus an RNAI (rifampin should not be used as monotherapy)		Linezolid or doxycycline or clindamycin plus rifampin
Regimen 6. Two PSIs from different antimicrobial drug classes		Linezolid plus doxycycline
Regimen 7. A single bactericidal drug		Meropenem
Regimen 8. A single PSI		Linezolid or doxycycline or clindamycin
First-line antimicrobial drug††
Bactericidal drug		PSI
Treatment (listed drugs joined by “or” are considered equivalent)	Dosage	Treatment	Dosage
Meropenem§§	2 g every 8 hours IV	Doxycycline¶¶	200 mg x 1 dose IV, then 100 mg every 12 hours IV
or
Ciprofloxacin¶¶	400 mg every 8 hours IV
or
Levofloxacin¶¶	500 mg every 12 hours IV
PCN-S only:
Penicillin G¶¶	4 million units every 4 hours IV
or
Ampicillin§§	2 g every 4 hours IV
Imipenem/cilastatin§§	1 g every 6 hours IV
or
Ampicillin/sulbactam§§	3 g every 6 hours IV
Alternative antimicrobial drug***
Bactericidal drug		PSI/RNAI
Treatment	Dosage	Treatment	Dosage
Piperacillin/tazobactam§§	3.375 g every 4 hours IV	Omadacycline§§,†††	200 mg x 1 dose IV on day 1, then 100 mg every 24 hours IV
Moxifloxacin§§	400 mg every 24 hours IV	Eravacycline§§,†††	1 mg/kg every 12 hours IV
Vancomycin§§,†††	15 mg/kg every 12 hours IV over a period of 1–2 hours (target AUC24 of 400–600 µg x h/mL [preferred]; if AUC24 is not available, maintain serum trough concentrations of 15–20 µg/mL). Consider a loading dose of 20-35 mg/kg for critically ill patients.	Clindamycin§§	900 mg every 8 hours IV
		Linezolid§§	600 mg every 12 hours IV
		Rifampin§§,§§§	600 mg every 12 hours IV
plus
Antitoxin (single dose as an adjunct to antimicrobial drug; listed antitoxins joined by “or” are considered equivalent)
Treatment		Dosage
Raxibacumab¶¶¶		40 mg/kg IV
or
Obiltoxaximab¶¶¶		16 mg/kg IV
AIGIV		420 units IV

Abbreviations: AIGIV = anthrax immunoglobulin intravenous; AUC₂₄ = area under the concentration-time curve from 0 to 24 hours; FDA = Food and Drug Administration; IV = intravenous; PCN-S = penicillin-susceptible strains; PEPAbx = antimicrobial postexposure prophylaxis for anthrax; PSI = protein synthesis inhibitor; RNAI = RNA synthesis inhibitor.

* Definitive therapy should be directed by antibiotic susceptibility test results, when available.

^† Pregnant adolescents: refer to pediatric guidelines for weight-based dosing (see Table 14).

^§ Dosing recommended for pregnant persons regardless of trimester. If meningitis is not suspected and susceptibilities are known, start at regimen 2.

^¶ “Systemic” was defined as including evidence of organ damage or any of the following: hyperthermia or hypothermia, tachycardia, tachypnea, hypotension, or leukocytosis or leukopenia (Source: Katharios-Lanwermeyer S, Holty JE, Person M, et al. Identifying meningitis during an anthrax mass casualty incident: systematic review of systemic anthrax since 1880. Clin Infect Dis 2016;62:1537–45).

** For anthrax meningitis, consider using antimicrobial drugs that have demonstrated potential neuroprotective benefits in vivo (e.g., minocycline, doxycycline, clindamycin, and ß-lactamase inhibitors).

^†† For highly bioavailable antimicrobial drugs (e.g., ciprofloxacin, doxycycline, and linezolid), if the IV formulation is not available, oral formulations can be considered for patients with an intact gastrointestinal tract where absorption is expected to be complete after oral administration.

^§§ Not approved by FDA for anthrax PEPAbx or treatment.

^¶¶ Approved by FDA for anthrax PEPAbx, treatment, or both, but specific uses (e.g., doses, dosing schedules, and patient populations) recommended in this report might differ from the FDA-approved labeling.

*** Alternative selections are for patients who have contraindications to or cannot tolerate first-line antimicrobial drugs or if first-line antimicrobial drugs are not available.

^††† This antimicrobial does not cross an intact blood-brain barrier but can cross with meningitis because of breakdown of the barrier.

^§§§ Rifampin is an RNAI and also bactericidal; however, it should not be used as monotherapy.

^¶¶¶ Premedicate with IV or oral diphenhydramine within 1 hour before administration. Hypersensitivity and anaphylaxis have been reported after raxibacumab and obiltoxaximab administration.

**** An 840-unit dose of AIGIV can be considered for severe cases.