Adults

Usually 1 tablet daily, or as directed by the physician. In severe cases, dosage may be increased.

Elderly

No specific dosage adjustment required, but caution is advised in cases of severe renal impairment.

Renal_impairment

No specific dosage adjustment generally required for mild to moderate impairment. Consult physician for severe renal impairment.

Onset

Effects are generally gradual, with clinical improvement observed over days to weeks depending on the severity of the deficiency.

Excretion

Excreted primarily via the kidneys in urine. Excess water-soluble vitamins are generally eliminated rapidly.

Half life

Thiamine: 90-180 minutes (in plasma), Pyridoxine: 15-20 days (for pyridoxal phosphate), Cyanocobalamin: Approximately 6 days (in plasma), with tissue half-life much longer.

Absorption

Readily absorbed from the gastrointestinal tract, primarily in the small intestine. Thiamine is actively transported at low concentrations and passively diffused at high concentrations. Pyridoxine is readily absorbed, and Cyanocobalamin requires intrinsic factor for active absorption from the ileum.

Metabolism

All three vitamins are metabolized primarily in the liver. Thiamine is phosphorylated to active forms. Pyridoxine is converted to pyridoxal phosphate. Cyanocobalamin is converted to methylcobalamin and adenosylcobalamin.

Levodopa

High doses of Pyridoxine (Vitamin B6) may decrease the therapeutic effect of Levodopa, particularly when used without a decarboxylase inhibitor.

Folic Acid/Methotrexate

Large doses of folic acid may mask B12 deficiency.

Phenobarbital/Phenytoin

May alter the metabolism of Pyridoxine.

Isoniazid, Cycloserine, Hydralazine, Penicillamine

These drugs are pyridoxine antagonists and can lead to B6 deficiency.