Hydroxocobalamin (OHCbl) is a natural analog of vitamin B-12, a basic member of the cobalamin family of compounds. It has an intense red color. Vitamin B12 is a term that refers to a group of compounds called cobalamins that are available in the human body in a variety of mostly interconvertible forms.

Methylcobalamin is a cobalamin (MeB12) used in peripheral neuropathy, diabetic neuropathy etc. It is a form of vitamin B₁₂. This vitamer is one of two active coenzymes used by B-12 dependent enzymes in the body, and is specifically the B-12 form used by 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), also known as methionine synthase.

Niacin, also known as vitamin B3 or nicotinic acid, is an organic compound with the formula C₅H₄NCO₂H. This colourless, water-soluble solid is a derivative of pyridine, with a carboxyl group (COOH) at the 3-position. Other forms of vitamin B3 include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH2), as well as more complex amides and a variety of esters.

Nicotinamide, also known as niacinamide and nicotinic acid amide, is the amide of nicotinic acid (vitamin B3 / niacin). Nicotinamide is a water-soluble vitamin and is part of the vitamin B group. Nicotinic acid, also known as niacin, is converted to nicotinamide in vivo, and though the two are identical in their vitamin functions, nicotinamide does not have the same pharmacologic and toxic effects of niacin, which occur incidental to niacin's conversion.