Hydroxocobalamin should be used with caution in patients with any known anaphylactic reaction to the drug or any of the formulation components. It is also contraindicated for patients hypersensitive to cobalt and cyanocobalamin. Cases have been reported where patients who tolerated cyanocobalamin without any adverse effects were found to be allergic to hydroxocobalamin.
Vitamin B12 deficiency can suppress the symptoms of polycythemia vera. Treatment with hydroxocobalamin, or cyanocobalamin, may unmask this condition.
Postmarketing reports have associated intravenous hydroxocobalamin therapy when used as a cyanide antidote with the development of renal impairment and crystalluria with hemodialysis being necessary in some cases for recovery. It is recommended to monitor the renal function during of the patients for 7 days following administration of hydroxocobalamin.
Because of rapid restoration of erythropoiesis in the bone marrow when severe megaloblastic anaemia is treated with hydroxocobalamin, hypokalemia, that is, low serum potassium can occur. ] Use of hydroxocobalamin for treating megaloblastic anaemia in combination with folate is also known to cause tremors and thrombocytosis. Therefore, potassium levels and platelet counts should be closely monitored when hydroxocobalamin is used for treatment of megaloblastic anaemia.
The red colour induced by OHCbl can interfere in several lab reports including bilirubin, creatinine, magnesium, serum iron, serum aspartate aminotransferase, COHb, methemoglobin, and oxyhemoglobin tests. Caution is advised when being administered to dialysis patients since it can also create a false alarm within dialysis machines and shuts down the machine due to what is referred to as “blood leak.”
Hydroxocobalamin can absorb visible UV light and therapy with this medication may cause photosensitivity. Its use can induce erythema and although it is unknown whether hydroxocobalamin-induced erythema increases the risk for photosensitivity, it is recommended that patients avoid direct sunlight until the redness of skin causes by usage of hydroxocobalamin has resolved.
Simultaneous administration of blood products including whole blood, packed red cells, platelets, and fresh frozen plasma, in the same intra venous line as hydroxocobalamin should be avoided.