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Serious adverse reactions with hydroxocobalamin include allergic reactions and increases in blood pressure [see WARNINGS AND PRECAUTIONS].

Clinical Studies Experience

Because clinical trials were conducted under widely varying conditions, adverse reaction rates observed in the clinical trials may not reflect the rates observed in practice.

Experience in Healthy Subjects

A double-blind, randomized, placebo-controlled, single-ascendingdose (2.5, 5, 7.5, and 10 g) study was conducted to assess the safety, tolerability, and pharmacokinetics of hydroxocobalamin in 136 healthy adult subjects. Because of the dark red color of hydroxocobalamin, the two most frequently occurring adverse reactions were chromaturia (red-colored urine) which was reported in all subjects receiving a 5 g dose or greater; and erythema (skin redness), which occurred in most subjects receiving a 5 g dose or greater. Adverse reactions reported in at least 5% of the 5 g dose group and corresponding rates in the 10 g and placebo groups are shown in Table 3.

Table 3 Incidence of Adverse Reactions Occurring in > 5% of Subjects in 5 g Dose Group and Corresponding Incidence in 10 g Dose Group and Placebo

In this study, the following adverse reactions were reported to have occurred in a dose-dependent fashion and with greater frequency than observed in placebo-treated cohorts: increased blood pressure (particularly diastolic blood pressure), rash, nausea, headache and infusion site reactions. All were mild to moderate in severity and resolved spontaneously when the infusion was terminated or with standard supportive therapies.

Other adverse reactions reported in this study and considered clinically relevant were:

• Eye disorders: swelling, irritation, redness
• Gastrointestinal disorders: dysphagia, abdominal discomfort, vomiting, diarrhea, dyspepsia, hematochezia
• General disorders and administration site conditions: peripheral edema, chest discomfort
• Immune system disorders: allergic reaction
• Nervous system disorders: memory impairment, dizziness
• Psychiatric disorders: restlessness
• Respiratory, thoracic and mediastinal disorders: dyspnea, throat tightness, dry throat
• Skin and subcutaneous tissue disorders: urticaria, pruritus
• Vascular disorders: hot flush

Experience in Known or Suspected Cyanide Poisoning Victims

Four open-label, uncontrolled, clinical studies (one of which was prospective and three of which were retrospective) were conducted in known or suspected cyanide-poisoning victims. A total of 245 patients received hydroxocobalamin treatment in these studies. Systematic collection of adverse events was not done in all of these studies and interpretation of causality is limited due to the lack of a control group and due to circumstances of administration (e.g., use in fire victims). Adverse reactions reported in these studies listed by system organ class included:

• Cardiac disorders: ventricular extrasystoles
• Investigations: electrocardiogram repolarization abnormality, heart rate increased
• Respiratory, thoracic, and mediastinal disorders: pleural effusion

Adverse reactions common to both the studies in known or suspected cyanide poisoning victims and the study in healthy volunteers are listed in the healthy volunteer section only and are not duplicated in this list.

No formal drug interaction studies have been conducted with Cyanokit.

Last reviewed on RxList: 5/26/2011
This monograph has been modified to include the generic and brand name in many instances.