Changes in blood pressure after administration of hydroxocobalamin: relationship to changes in plasma cobalamins-(III) concentrations in healthy volunteers.

OBJECTIVE: To assess the relationship between blood pressure changes following infusion of antidotal doses of hydroxocobalamin and plasma concentrations of total and free cobalamins-(III).

METHODS: Independent groups of healthy volunteers received single intravenous doses of 2.5, 5, 7.5, or 10 g hydroxocobalamin over 7.5 to 30 minutes.

RESULTS: In the pharmacokinetic population (n = 41), hydroxocobalamin caused short-lived mean blood pressure increases. Blood pressure increased shortly after initiation of infusion and returned nearly to baseline by 4 hours post-infusion. The time course of blood pressure changes coincided with that of changes in plasma total and free cobalamins-(III). Change in mean arterial pressure (MAP) was strongly correlated with plasma area-under-the-concentration-time curves (AUCs) of total and free cobalamins-(III) during infusion (r > 0.7) but not through 24 hours post-infusion (r < or = 0.36).

CONCLUSION: The short-lived increase in mean blood pressure during administration of antidotal doses of hydroxocobalamin is closely linked to initial exposure to total and free cobalamins-(III).