Version July 2025
Hypersensitivity and anaphylaxis have been reported during the intravenous infusion of obiltoxaximab. Due to the risk of hypersensitivity and anaphylaxis, obiltoxaximab should be administered in monitored settings by personnel trained and equipped to manage anaphylaxis. Monitor individuals who receive obiltoxaximab closely for signs and symptoms of hypersensitivity reactions throughout the infusion and for a period of time after administration. Stop obiltoxaximab infusion immediately and treat appropriately if hypersensitivity or anaphylaxis occurs.
Anthrax:
Note: Premedicate with diphenhydramine within 1 hour prior to infusion (Ref). Consult public health officials for event-specific recommendations.
Inhalational (postexposure prophylaxis): Note: For use when antimicrobial agents are not available or appropriate (Ref).
≤40 kg: IV: 24 mg/kg/dose as a single dose (Ref).
>40 kg: IV: 16 mg/kg/dose as a single dose (Ref).
Cutaneous, without meningitis, treatment (off-label use): Note: For use when antimicrobial agents are not available or appropriate (Ref).
IV: 16 mg/kg as a single dose (Ref).
Systemic (including meningitis), treatment (adjunctive agent): Note: Use in combination with appropriate antimicrobials (Ref).
≤40 kg: IV: 24 mg/kg/dose as a single dose (Ref).
>40 kg: IV: 16 mg/kg/dose as a single dose (Ref).
There are no dosage adjustments provided in the manufacturer's labeling; however, a small clearance rate (L/day) suggests that there is minimal renal clearance (Hou 2017).
There are no dosage adjustments provided in the manufacturer's labeling
Refer to adult dosing
(For additional information see "Obiltoxaximab (United States: Availability limited to Strategic National Stockpile distribution): Pediatric drug information")
Note: Premedicate with diphenhydramine prior to infusion.
Anthrax, inhalational, treatment and prophylaxis: Infants, Children, and Adolescents:
≤15 kg: IV: 32 mg/kg as a single dose
>15 kg to 40 kg: IV: 24 mg/kg as a single dose
>40 kg: IV: 16 mg/kg as a single dose
There are no dosage adjustments provided in the manufacturer’s labeling.
There are no dosage adjustments provided in the manufacturer’s labeling.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Adverse reactions reported in adults.
>10%:
Hypersensitivity: Hypersensitivity reaction (11%)
Nervous system: Headache (8% to 16%)
1% to 10%:
Cardiovascular: Chest discomfort (<2%), chest pain (<2%), palpitations (<2%)
Dermatologic: Pruritus (4%), skin rash (7%), urticaria (2%)
Gastrointestinal: Vomiting (<2%), xerostomia (<2%)
Hematologic & oncologic: Abnormal lymphocytes (decreased: <2%), decreased neutrophils (<2%), decreased white blood cell count (<2%)
Immunologic: Antibody development (3%)
Local: Bruising at injection site (3%), erythema at injection site (4%), infusion-site pain (2%), skin discoloration at injection site (<2%), swelling at injection site (3%)
Nervous system: Dizziness (<2%), fatigue (<2%), voice disorder (<2%)
Neuromuscular & skeletal: Increased creatine phosphokinase in blood specimen (<2%), limb pain (2%), musculoskeletal pain (<2%), myalgia (<2%)
Respiratory: Cough (3% to 8%), cyanosis (<2%), dyspnea (<2%), nasal congestion (2%), oropharyngeal pain (<2%), paranasal sinus congestion (<2%), rhinorrhea (3%), throat irritation (3%), upper respiratory tract infection (5%)
Miscellaneous: Fever (<2%)
<1%: Hypersensitivity: Anaphylaxis
There are no contraindications listed in the manufacturer's labeling.
Concerns related to adverse effects:
• Hypersensitivity: [US Boxed Warning]: Hypersensitivity or anaphylactic reactions (eg, rash/urticaria, cough, dyspnea, cyanosis, postural dizziness, chest discomfort) may occur. Administer in a monitored setting; monitor patients closely for signs and symptoms of hypersensitivity during and after the infusion. If hypersensitivity or anaphylaxis occurs, discontinue the infusion immediately and treat appropriately.
Dosage form specific issues:
• Polysorbate 80: Some dosage forms may contain polysorbate 80 (also known as Tweens). Hypersensitivity reactions, usually a delayed reaction, have been reported following exposure to pharmaceutical products containing polysorbate 80 in certain individuals (Isaksson 2002; Lucente 2000; Shelley 1995). Thrombocytopenia, ascites, pulmonary deterioration, and renal and hepatic failure have been reported in premature neonates after receiving parenteral products containing polysorbate 80 (Alade 1986; CDC 1984). Refer to manufacturer's labeling.
May be product dependent
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Intravenous:
Anthim: 600 mg/6 mL (6 mL) [contains polysorbate 80]
Obiltoxaximab (ANTHIM) is not available for general public use. All supplies are currently owned by the federal government for inclusion in the Strategic National Stockpile and for use by the US military.
IV: Premedication with diphenhydramine within 1 hour before administration is recommended (Ref). Administer prepared solution (IV infusion bag or syringe) using a 0.22-micron inline filter over 1 hour and 30 minutes. Flush the line with NS at the end of the infusion.
IV: Must be diluted prior to administration. Administer over 90 minutes using a 0.22 micron inline filter. Flush the line with NS at the end of the infusion. Premedication with diphenhydramine is recommended.
Anthrax, inhalational (postexposure prophylaxis): Prophylaxis of inhalational anthrax due to Bacillus anthracis when alternative therapies are not available or not appropriate.
Limitations of use: Should only be used for prophylaxis when the benefit for prevention of inhalational anthrax outweighs the risk of hypersensitivity and anaphylaxis.
Anthrax, systemic, treatment (inhalational exposure): Treatment of inhalational anthrax due to B. anthracis in combination with appropriate antibacterial drugs.
Anthrax, cutaneous, treatment
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Efgartigimod Alfa: May decrease therapeutic effects of Fc Receptor-Binding Agents. Risk C: Monitor
Nipocalimab: May decrease therapeutic effects of Fc Receptor-Binding Agents. Risk C: Monitor
Rozanolixizumab: May decrease therapeutic effects of Fc Receptor-Binding Agents. Risk C: Monitor
Obiltoxaximab is a chimeric monoclonal antibody (IgG1). Human IgG crosses the placenta. Fetal exposure is dependent upon the IgG subclass, maternal serum concentrations, placental integrity, newborn birth weight, and GA, generally increasing as pregnancy progresses. The lowest exposure would be expected during the period of organogenesis and the highest during the third trimester (Clements 2020; Palmeira 2012; Pentsuk 2009).
Obiltoxaximab may be used for the management of B. anthracis in pregnant patients when other options are not available or appropriate. Maternal infection with B. anthracis may cause preterm labor, fetal infection, fetal distress, or fetal loss. Maternal death may also occur. Obiltoxaximab is an alternative option for the treatment of cutaneous anthrax without CNS involvement and for the postexposure prophylaxis of B. anthracis during pregnancy. Obiltoxaximab may be used as an alternative treatment of systemic anthrax (with or without CNS involvement) in combination with an antimicrobial agent. The dose of obiltoxaximab in pregnant and postpartum patients is the same as in nonpregnant adults (CDC [Bower 2023]; Meaney-Delman 2014).
It is not known if obiltoxaximab is present in breast milk.
Obiltoxaximab is a chimeric monoclonal antibody (IgG1). Maternal IgG is present in breast milk. According to the manufacturer, the decision to breastfeed during therapy should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and benefits of treatment to the mother.
Recommendations for using obiltoxaximab in the management of B. anthracis in breastfeeding patients are the same as in pregnancy. Exposure to anthrax is not considered a contraindication to breastfeeding; however, if there are active cutaneous lesions on the breast, contact with the infant should be avoided and feeding from the affected breast should not occur until >48 hours of appropriate antibiotic therapy (CDC [Bower 2023]; Meaney-Delman 2014).
Monitor patients closely for signs and symptoms of hypersensitivity during and after the infusion.
Obiltoxaximab is a monoclonal antibody that binds the free protective antigen component of B. anthracis toxin thereby preventing the intracellular entry of the anthrax lethal factor and edema factor, the enzymatic toxin components responsible for the pathogenic effects of anthrax toxin.
Distribution: Greater than plasma volume (eg, some tissue distribution).
Excretion: Minimal renal elimination
