Vitamin B-Complex

B vitamins play different roles but their functions are inter-related and complementary. They work as coenzyme in several biochemical reactions to activate enzyme reaction of corresponding protein by creating holoenzyme. As holoenzyme they participate in the majority of cellular processes.

Although vitamin B1 and B6 participate more actively in the methionine cycle and citric acid cycle, which is the mitochondrial energy production process, the entire vitamin B group is involved in its successful execution. B vitamins also help to maintain the health of nervous system by playing a crucial role in the central nervous system and the peripheral nervous system functions.

Vitamin B1 (thiamine) serves as a coenzyme with transketolase enzyme in the pentose phosphate pathway of glycolysis. This pathway generates pentose sugar for synthesis of amino acid and nucleic acid and converts glucose to ribulose-5-phosphate via retrieving the carbon from the pentose phosphate shunt.Vitamin B2 (Riboflavin) plays an important role in many biologically important redox reactions such as energy producing, biosynthetic, detoxifying and electron scavenging pathways as a precursor of coenzyme flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Riboflavin is also essential for the metabolism of homocysteine, as a cofactor for methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR).

In the citric acid cycle, Vitamin B3 (Niacin) is involved in the formation of acetyl-CoA while conversion of its co-enzyme takes places from NAD+ (nicotinamide adenine dinucleotide) to NADH. In the anabolic methionine cycle, niacin, in the form of NAD, is a necessary co-factor for the enzymes dihydrofolate reductase in the folate/tetrahydrobiopterin cycle and S-adenosylhomocysteine hydrolase. Vitamin B5 (Dexpanthenol) is a component of coenzyme A. At least 70 enzymes utilize coenzyme A for the metabolism of fat, protein, carbohydrates and proper functioning of citric acid cycle. It is also involved in synthesis of several neural transmitters.

Vitamin B6 (Pyridoxine) acts as a necessary cofactor in the folate cycle and combines with serine hydroxymethyl transferase to effect the conversion of tetrahydrofolate(THF) to 5,10 methylene THF. B6 is a rate limiting cofactor in the synthesis of several neurotransmitters such as dopamine, serotonin, γ-aminobutyric acid (GABA), noradrenaline and the hormone melatonin.

Intravenous administration of Vitamin B preparations should be done slowly and if necessary, the preparation should be diluted to avoid speed reaction. The patient should be questioned closely about any symptoms from previous doses to prevent severe reactions. A skin sensitivity test prior to administration is advised. For the older patients (60+ years) specially with arteriosclerosis, possibility of circulatory collapse after administration should be kept in mind.

Anaphylactic shock due to intravenous administration of vitamin B complex has been reported earlier.

Thiamine hydrochloride (vitamin B1) in the formulation is known to cause life threatening anaphylaxis especially on multiple administrations if patient is allergic to it. Less threatening reaction to B1 include anxiety, pruritus, respiratory distress, nausea, abdominal pain. Vomiting, anorexia, headache, irritability, tremors, and palpitations, can be overdose syndromes.

Side effects from vitamin B2 in the preparation are rare but skin test or when necessary the more sensitive intradermal skin test may be advised to diagnose anaphylactic sensitivity.

Larger doses of niacin tend to cause nausea and vomiting. In the blood stream as nicotinic acid, it can cause skin flush and this reaction is actually responsible for the tolerable upper limit (UL) for niacin at 35 mg/d for adults in US.

Vitamins B5 and H have reported to cause life-threatening adverse reaction of eosinophilic pleuropericarditis and patient history for such allergy should be checked before administration.

Prolonged overdose of B6 (150-200 mg/day) over weeks can cause severe sensory-nervous-system dysfunction and ataxia.[23 ]With normal usage serious adverse effects are not reported for pyridoxine (vitamin B6), however, diarrhea, emesis, and rosacea-like dermatitis may be observed in some cases.

Vitamins from the B group are generally recommended during pregnancy as per individual requirements. No specific safety data could be identified. Physician’s advice before use is recommended.

Vitamins from the B group are generally recommended during breastfeeding as per individual requirements. These vitamins pass through the breast milk to the infant. No specific safety data could be identified. Physician’s advice before use is recommended.

Store this medication in a refrigerator at 36°F to 46°F (2°C to 8°C). Keep all medicines out of the reach of children. Throw away any unused medicine after the beyond use date. Do not flush unused medications or pour down a sink or drain.