Pharmacokinetics

  1. Single-dose administration

Mecobalamin was administered intramuscularly or intravenously to 12 healthy adult male volunteers at a single dose of 500 mcg. The time to reach peak serum total vitamin B12  (abbrevia ted to B12) concentration (tmax) was 0.9 hr after intramuscular administration and immediately to

3 mins. after intravenous administration, and the increment (except endogenous serum total B12) in peak serum total vitamin B12 concentration (ΔCmax) was 22.4 ng/mL after intramuscular administration and 85.0 ng/mL after intravenous administration.

The area under the serum total B12 concentration-time curve (ΔAUC) calculated by increment of the actual values at 144 hr. after administration was 204.1 ng•hr/mL after intramuscular administration and 358.6 ng•hr/mL after intravenous administration.

On the other hand, the rate of binding saturation showed a similar increase in both groups of subjects for 144 hr. after administration.

Serum total vitamin B12 concentration after single administration of Mecobalamin (METHYCOBAL®) Injection 500 mcg

 

Pharmacokinetic parameters after a single dose administration of Mecobalamin (METHYCOBAL®) Injection 500 mcg

Tmax (hr) ΔCmax (ng/mL) ΔAUC0-4C (ng•hr/mL) T1/2 (hr)
I.V 0-3 min 85.0 ± 8.9 358.6 ± 34.4 27.1
I.M 0.9 ± 0.1 22.4 ± 1.1 204.1 ± 12.9 29
Note: The incidence of adverse reactions includes the post-marketing surveillance

 

 

  1. Repeated-dose administration

Mecobalamin was administered intravenously to 6 healthy adult male volunteers at a single dose of 500 mcg daily for 10 consecutive days. Serum total B12 concentration determined before each administration increased from day to day. After 2 days of administration, the serum total B12 concentration was 5.3±1.8 ng/mL, about 1.4 times the 24 hr value (3.9±1 2 ng/mL) after administration. At 3 days of administration it had increased to 6.8±1.5 ng/mL, about 1.7 times the 24 hr value, and this concentration was maintained until the last dosing.