Effect of Administration Route on the Pharmacokinetics of Cobalamin in Elderly Patients: A Randomized Controlled Trial

BACKGROUND The gold standard for cobalamin deficiency treatment is administration of cobalamin by intramuscular injection. The injection is painful and inconvenient, particularly for elderly persons. Cobalamin might also be administered intranasally. Previous studies do not provide insight into the pharmacokinetics of intranasal cobalamin administration in comparison with cobalamin injection. AIM To quantify the pharmacokinetics of intranasally and intramuscularly administered cobalamin to determine if intranasal administration might be an alternative for intramuscular administration. METHODS Ten inpatients and outpatients of a geriatrics unit were recruited and randomly assigned to receive a single dose of 1000 μg cobalamin administered either by intranasal spray or intramuscular injection (5 per group). Inclusion criteria were written informed consent, age >65 years, and a cobalamin serum concentration <200 pmol/L. Total cobalamin serum concentrations were determined 10 times within 48 hours after administration. The differences in Cmax, Tmax, and AUC0-48 h per administration route were statistically compared using ANOVA. RESULTS The average Cmax was 1 nmol/L after intranasal and 38.5 nmol/L after intramuscular administration. The average Tmax for intranasal and intramuscular administration was 42 minutes versus 342 minutes, respectively, and the AUC0-48 h was 1.3 µmol/L/min versus 45.4 µmol/L/min, respectively. These values also differed significantly (P<0.05). The estimated bioavailability of the intranasal administration was 2%. CONCLUSIONS The pharmacokinetics of intranasal and intramuscular cobalamin administration in elderly, cobalamin-deficient patients differ significantly. However, the estimated 2% bioavailability of cobalamin after intranasal administration makes intranasal cobalamin administration a potentially interesting administration route for elderly patients. Netherlands Trial Registry identifier: NTR 3005.