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Pharmacology: Pharmacodynamics: Pregabalin: Pregabalin, is a gamma-aminobutyric acid analogue ((S)-3-(aminomethyl)-5-methylhexanoic acid). Pregabalin binds to an auxiliary subunit (α2-δ protein) of voltage-gated calcium-channels in the central nervous system, potently displacing [3H]-gabapentin.
Methylcobalamin: Methylcobalamin is one of the two coenzyme forms of vitamin B12 (the other being adenosylcobalamin). It is a cofactor in the enzyme methionine synthase which functions to transfer methyl groups for the regeneration of methionine from homocysteine.
Pharmacokinetics: Pregabalin: Pregabalin is rapidly absorbed when administered in the fasted state, with peak plasma concentrations occurring within 1 hour. Oral bioavailability is estimated to be 90% and is independent of dose. Food results in a decrease in Cmax by 25-30% and a delay in tmax to ~2.5 hours. However, administration of pregabalin with food has no clinically significant effect on the extent of pregabalin absorption. The apparent volume of distribution of pregabalin is 0.56 l/kg. Pregabalin is not bound to plasma proteins. Pregabalin undergoes negligible metabolism. 98% of unchanged pregabalin is recovered in urine. The N-methylated derivative of pregabalin is the major metabolite. Pregabalin is eliminated from the systemic circulation primarily by renal excretion as unchanged drug. Pregabalin mean elimination half-life is 6.3 hours.
Methylcobalamin: Methylcobalamin is utilized more efficiently than cyanocobalamin to increase levels of one of the coenzyme forms of vitamin B12. The quantity of cobalamin detected following a small oral dose of methylcobalamin is similar to the amount following administration of cyanocobalamin; but significantly more cobalamin accumulates in liver tissue following administration of methylcobalamin. Human urinary excretion of methylcobalamin is about one-third that of a similar dose of cyanocobalamin, indicating substantially greater tissue retention.
