HYDROXOCOBALAMIN Drug Interactions: What You Need to Know

INTERACTIONS Formal drug interaction studies have not been conducted with CYANOKIT. Interference with Laboratory Tests Because of its deep red color, hydroxocobalamin has been found to interfere with colorimetric determination of certain laboratory parameters (e.g., clinical chemistry, hematology, coagulation, and urine parameters). Be aware of this when reporting and interpreting laboratory results [see Warnings and Precautions ( 5.5 )].

CONTRAINDICATION Hypersensitivity to any component of this medication.

AND PRECAUTIONS Risk of Anaphylaxis and Other Hypersensitivity Reactions : Consider alternative therapies, if available, in patients with known anaphylactic reactions to hydroxocobalamin or cyanocobalamin. ( 5.2 ) Risk of Renal Injury : Acute renal failure with acute tubular necrosis, renal impairment and urine calcium oxalate crystals have been reported following CYANOKIT therapy. Monitor renal function for 7 days following CYANOKIT therapy. ( 5.3 ) Risk of Increased Blood Pressure : Substantial increases in blood pressure may occur following CYANOKIT therapy. Monitor blood pressure during treatment. ( 5.4 )

5.1 Emergency Patient Management In conjunction with CYANOKIT, treatment of cyanide poisoning must include immediate attention to airway patency, adequacy of oxygenation and hydration, cardiovascular support, and management of seizures. Consideration should be given to decontamination measures based on the route of exposure.

5.2 Risk of Anaphylactic and Other Hypersensitivity Reactions Use caution in the management of patients with known anaphylactic reactions to hydroxocobalamin or cyanocobalamin. Consider alternative therapies, if available. Allergic reactions may include: anaphylaxis, chest tightness, edema, urticaria, pruritus, dyspnea, and rash. Allergic reactions including angioneurotic edema have also been reported in postmarketing experience.

5.3 Risk of Renal Injury Cases of acute renal failure with acute tubular necrosis, renal impairment, and urine calcium oxalate crystals have been reported. In some situations, hemodialysis was required to achieve recovery. Regular monitoring of renal function, including but not limited to blood urea nitrogen (BUN) and serum creatinine, should be performed for 7 days following CYANOKIT therapy.

5.4 Risk of Increased Blood Pressure Many patients with cyanide poisoning will be hypotensive; however, elevations in blood pressure have also been observed in known or suspected cyanide poisoning victims. Elevations in blood pressure (≥180 mmHg systolic or ≥110 mmHg diastolic) were observed in approximately 18% of healthy subjects (not exposed to cyanide) receiving hydroxocobalamin 5 g and 28% of subjects receiving 10 g. Increases in blood pressure were noted shortly after the infusions were started; the maximal increase in blood pressure was observed toward the end of the infusion. These elevations were generally transient and returned to baseline levels within 4 hours of dosing. Monitor blood pressure during treatment with CYANOKIT.

5.5 Interference with Clinical Laboratory Evaluations and Clinical Methods Clinical Laboratory Evaluations Because of its deep red color, hydroxocobalamin has been found to interfere with colorimetric determination of certain laboratory parameters (e.g., clinical chemistry, hematology, coagulation, and urine parameters). In vitro tests indicated that the extent and duration of the interference are dependent on numerous factors such as the dose of hydroxocobalamin, analyte, methodology, analyzer, hydroxocobalamin concentration, and partially on the time between sampling and measurement. The data presented in Table 2 is collected from in vitro studies and pharmacokinetic data in healthy volunteers and describes laboratory interference that may be observed following a 5 g dose of hydroxocobalamin. Interference following a 10 g dose can be expected to last up to an additional 24 hours. The extent and duration of interference in cyanide-poisoned patients may differ. In addition, results may vary substantially from one analyzer to another. Be aware of this when reporting and interpreting laboratory results.

Table

2 Laboratory Interference Observed with in vitro Samples of Hydroxocobalamin Laboratory Parameter No Interference Observed Artificially Increased * Artificially Decreased * Un-predictable Duration of Interference * ≥10% interference observed on at least 1 analyzer Analyzers used: ACL Futura (Instrumentation Laboratory), AxSYM ® /Architect ™ (Abbott), BM Coasys 110 (Boehringer Mannheim), CellDyn 3700 ® (Abbott), Clinitek ® 500 (Bayer), Cobas Integra ® 700, 400 (Roche), Gen-S Coultronics, Hitachi 917, STA ® Compact, Vitros ® 950 (Ortho Diagnostics)

Clinical Chemistry Calcium Sodium Potassium

Chloride Urea GGT Creatinine Bilirubin Triglycerides Cholesterol Total protein Glucose Albumin Alkaline phosphatase ALT Amylase Phosphate Uric Acid AST CK CKMB LDH 24 hours with the exception of bilirubin (up to 4 days)

Hematology Erythrocytes

Hematocrit MCV Leukocytes Lymphocytes Monocytes Eosinophils Neutrophils Platelets Hemoglobin MCH MCHC Basophils 12 - 16 hours Coagulation aPTT PT (Quick or INR) 24 - 48 hours Urinalysis pH (with all doses)

Glucose Protein Erythrocytes Leukocytes Ketones

Bilirubin Urobilinogen Nitrite pH (with equivalent doses of <5 g) 48 hours up to 8 days; color changes may persist up to 28 days Clinical Methods Because of its deep red color, hydroxocobalamin may cause hemodialysis machines to shut down due to an erroneous detection of a “blood leak”. This should be considered before hemodialysis is initiated in patients treated with hydroxocobalamin.

5.6 Photosensitivity Hydroxocobalamin absorbs visible light in the UV spectrum. It therefore has potential to cause photosensitivity. While it is not known if the skin redness predisposes to photosensitivity, patients should be advised to avoid direct sun while their skin remains discolored.

5.7 Use of Blood Cyanide Assay While determination of blood cyanide concentration is not required for management of cyanide poisoning and should not delay treatment with CYANOKIT, collecting a pretreatment blood sample may be useful for documenting cyanide poisoning as sampling post-CYANOKIT use may be inaccurate.