Ascorbic Acid 500 mg, Dextrose 1000 mg, Nicotinamide 160 mg / 5 ml, Pyridoxine 50 mg, Riboflavin 4 mg, Thiamine 250 mg / 5 ml Infusion

The exact mechanism of action of ascorbic acid for the treatment of symptoms and signs of scurvy (a disorder caused by severe deficiency in vitamin C) is unknown; however, administration of ascorbic acid in patients with scurvy is thought to restore the body pool of ascorbic acid.

In a single pharmacokinetic study, healthy male and female adults (n=8) were given a single intravenous dose of 1000 mg ascorbic acid (5 times the largest recommended single dose) infused over a 30 minute period. The mean peak exposure to ascorbic acid was 436.2 μM and occurred at the end of the 30 minute infusion.

Distribution — Ascorbic acid is distributed widely in the body, with large concentrations found in the liver, leukocytes, platelets, glandular tissues, and lens of the eye. Based on data from oral exposure, ascorbic acid is known to be distributed into breast milk and crosses the placental barrier.

Elimination — When the body is saturated with ascorbic acid, the plasma concentration will be about the same as that of the renal threshold; if further amounts are then administered, most of it is excreted in the urine. When body tissues are not saturated and plasma concentration is low, administration of ascorbic acid results in little or no renal excretion. The mean±SD (N=3) half-life observed in the single dose PK study, as described above, was 7.4±1.4 h.

Nicotinamide contributes to NAD and NADP coenzymes involved in cellular oxidation-reduction reactions.

The intravenous multivitamin reference describes plasma vitamin B3 in acid or amide forms and urinary elimination as unchanged substance or metabolites. It does not provide a nicotinamide-specific half-life or validate another injection mixture.

The water soluble vitamins are widely distributed in both plants and animals. They are absorbed in man by both diffusion and active transport mechanisms. These vitamins are structurally diverse (derivatives of sugar, pyridine, purines, pyrimidine, organic acid complexes and nucleotide complex) and act as coenzymes, as oxidation-reduction agents, possibly as mitochondrial agents. Metabolism is rapid, and the excess is excreted in the urine.

Thiamine is distributed in all tissues. The highest concentrations occur in liver, brain, kidney and heart. When thiamine intake is greatly in excess of need, tissue stores increase two to three times. If intake is insufficient, tissues become depleted of their vitamin content. Absorption of thiamine following IM administration is rapid and complete.

Thiamine combines with adenosine triphosphate (ATP) to form thiamine pyrophosphate, also known as cocarboxylase, a coenzyme. Its role in carbohydrate metabolism is the decarboxylation of pyruvic acid in the blood and α-ketoacids to acetaldehyde and carbon dioxide. Increased levels of pyruvic acid in the blood indicate vitamin B1 deficiency.

The requirement for thiamine is greater when the carbohydrate content of the diet is raised. Body depletion of vitamin B1 can occur after approximately three weeks of total absence of thiamine in the diet.

Dextrose restores blood glucose levels and provides a source of carbohydrate calories.

The exposure-response relationship and time course of pharmacodynamic response for the safety and effectiveness of dextrose have not been fully characterized.

Natural substances that have vitamin B 6 activity are pyridoxine in plants and pyridoxal or pyridoxamine in animals. All 3 are converted to pyridoxal phosphate by the enzyme pyridoxal kinase. The physiologically active forms of vitamin B 6 are pyridoxal phosphate (codecarboxylase) and pyridoxamine phosphate. Riboflavin is required for the conversion of pyridoxine phosphate to pyridoxal phosphate.

Vitamin B 6 acts as a coenzyme in the metabolism of protein, carbohydrate, and fat. In protein metabolism, it participates in the decarboxylation of amino acids, conversion of tryptophan to niacin or to serotonin (5-hydroxtryptamine), deamination, and transamination and transulfuration of amino acids. In carbohydrate metabolism, it is responsible for the breakdown of glycogen to glucose-1-phosphate.

The total adult body pool consists of 16 to 25 mg of pyridoxine. Its half-life appears to be 15 to 20 days. Vitamin B 6 is degraded to 4-pyridoxic acid in the liver. This metabolite is excreted in the urine.

The need for pyridoxine increases with the amount of protein in the diet. The tryptophan load test appears to uncover early vitamin B 6 deficiency by detecting xanthinurea. The average adult minimum daily requirement is about 1.25 mg. The ‘‘Recommended Dietary Allowance’’ of the National Academy of Sciences is estimated to be as much as 2.2 mg for adults and 2.5 mg for pregnant and lactating women. The requirements are more in persons having certain genetic defects or those being treated with isonicotinic acid hydrazide (INHJ) or oral contraceptives.