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Wednesday, July 30, 2025

Vitamins


Definition and Scope

Vitamins are organic micronutrients required in small quantities for essential biochemical functions and metabolic processes in the human body. Unlike macronutrients (carbohydrates, proteins, fats), vitamins do not provide energy, but their absence leads to specific deficiency syndromes. They are divided into two major categories based on their solubility: fat-soluble vitamins and water-soluble vitamins. Each vitamin plays a unique role, acting as a coenzyme, antioxidant, hormone precursor, or regulator of cellular pathways.

While naturally obtained through diet, some individuals require pharmacological supplementation due to malabsorption, medical conditions, or dietary restrictions. In such cases, synthetic or semi-synthetic vitamin preparations are used as medicinal agents.

Classification of Vitamins

  1. Fat-Soluble Vitamins

    • Stored in adipose tissue and the liver

    • Absorbed with dietary fats and require bile salts

    • Risk of toxicity with over-supplementation

    Members:

    • Vitamin A (Retinoids and Carotenoids)

    • Vitamin D (Cholecalciferol, Ergocalciferol)

    • Vitamin E (Tocopherols and Tocotrienols)

    • Vitamin K (Phylloquinone, Menaquinone)

  2. Water-Soluble Vitamins

    • Not stored in significant amounts; excess excreted in urine

    • Require continuous dietary intake

    • Generally safer in overdose compared to fat-soluble ones

    Members:

    • Vitamin B Complex (B1, B2, B3, B5, B6, B7, B9, B12)

    • Vitamin C (Ascorbic Acid)

Detailed Overview of Each Vitamin and Generic Preparations

Fat-Soluble Vitamins

Vitamin A (Retinol, Retinal, Retinoic Acid, Beta-Carotene)

  • Functions: Vision (especially night vision), immune response, epithelial health, embryonic development

  • Deficiency: Night blindness, xerophthalmia, keratomalacia

  • Generic Names: Retinol, Retinyl palmitate, Retinyl acetate, Beta-carotene

  • Formulations: Oral capsules, injectables, topical creams (for dermatological use)

  • Examples:

    • Retinol (Vitamin A) capsules

    • Beta-carotene supplements

Vitamin D (D2 - Ergocalciferol, D3 - Cholecalciferol)

  • Functions: Calcium and phosphorus metabolism, bone mineralization, immune modulation

  • Deficiency: Rickets (children), osteomalacia (adults), hypocalcemia

  • Generic Names: Cholecalciferol (D3), Ergocalciferol (D2), Calcitriol (active form)

  • Formulations: Oral drops, tablets, soft gels, injectables

  • Examples:

    • Cholecalciferol 1000 IU capsules

    • Calcitriol 0.25 mcg soft gels

Vitamin E (Tocopherol and Tocotrienols)

  • Functions: Antioxidant protection of cell membranes, immunity, DNA repair

  • Deficiency: Hemolytic anemia (especially in premature infants), neuropathy

  • Generic Names: Alpha-tocopherol, D-alpha tocopheryl acetate

  • Formulations: Soft gels, capsules, topical creams

  • Examples:

    • Vitamin E (dl-alpha tocopherol) 400 IU capsules

Vitamin K (K1 - Phylloquinone, K2 - Menaquinones)

  • Functions: Coagulation factor synthesis (II, VII, IX, X), bone health

  • Deficiency: Bleeding tendency, elevated INR

  • Generic Names: Phytomenadione (K1), Menaquinone-7 (K2)

  • Formulations: Oral tablets, injectables (especially in neonatal care)

  • Examples:

    • Phytomenadione injection 10 mg/mL

    • Menaquinone-7 (MK-7) capsules

Water-Soluble Vitamins

Vitamin B1 (Thiamine)

  • Functions: Carbohydrate metabolism, nerve function (coenzyme in pyruvate dehydrogenase)

  • Deficiency: Beriberi, Wernicke-Korsakoff syndrome

  • Generic Names: Thiamine hydrochloride, Thiamine mononitrate

  • Formulations: Oral tablets, IM/IV injections

  • Examples:

    • Thiamine HCl injection 100 mg/mL

    • Thiamine tablets 100 mg

Vitamin B2 (Riboflavin)

  • Functions: Coenzyme in redox reactions (FAD/FMN), mucosal and skin health

  • Deficiency: Cheilitis, glossitis, seborrheic dermatitis

  • Generic Name: Riboflavin

  • Formulations: Oral tablets, included in multivitamin complexes

  • Examples:

    • Riboflavin 100 mg capsules

Vitamin B3 (Niacin, Nicotinamide)

  • Functions: Coenzyme (NAD/NADP), lipid metabolism

  • Deficiency: Pellagra (dermatitis, diarrhea, dementia)

  • Generic Names: Niacin (nicotinic acid), Niacinamide (nicotinamide)

  • Formulations: Immediate-release and extended-release tablets

  • Examples:

    • Niacin ER tablets 500 mg

    • Nicotinamide 250 mg

Vitamin B5 (Pantothenic Acid)

  • Functions: Component of Coenzyme A, involved in fatty acid metabolism

  • Deficiency: Rare; may cause fatigue, GI symptoms

  • Generic Name: Dexpanthenol, Calcium pantothenate

  • Formulations: Oral tablets, creams for skin/hair health

  • Examples:

    • Calcium pantothenate 500 mg

Vitamin B6 (Pyridoxine)

  • Functions: Neurotransmitter synthesis, amino acid metabolism

  • Deficiency: Neuropathy, anemia, seizures in infants

  • Generic Names: Pyridoxine hydrochloride

  • Formulations: Oral tablets, IV/IM injections

  • Examples:

    • Pyridoxine HCl tablets 50–100 mg

    • Injectable Pyridoxine 100 mg/mL

Vitamin B7 (Biotin)

  • Functions: Coenzyme in carboxylation reactions, hair and nail health

  • Deficiency: Dermatitis, alopecia, neurological symptoms

  • Generic Name: Biotin

  • Formulations: Oral capsules, dietary supplements

  • Examples:

    • Biotin 5 mg, 10 mg, 20 mg

Vitamin B9 (Folic Acid)

  • Functions: DNA synthesis, red blood cell production, neural tube development

  • Deficiency: Megaloblastic anemia, neural tube defects in fetus

  • Generic Names: Folic acid, L-methylfolate (active form)

  • Formulations: Tablets, injectables, prenatal formulations

  • Examples:

    • Folic acid tablets 400 mcg, 1 mg

    • L-methylfolate 7.5 mg

Vitamin B12 (Cobalamin)

  • Functions: DNA synthesis, nerve cell function, erythropoiesis

  • Deficiency: Pernicious anemia, neuropathy

  • Generic Names: Cyanocobalamin, Hydroxocobalamin, Methylcobalamin

  • Formulations: Oral tablets, sublingual, IM/IV injection

  • Examples:

    • Cyanocobalamin injection 1000 mcg/mL

    • Methylcobalamin tablets 500 mcg

Vitamin C (Ascorbic Acid)

  • Functions: Antioxidant, collagen synthesis, iron absorption, immune support

  • Deficiency: Scurvy (bleeding gums, joint pain, poor wound healing)

  • Generic Name: Ascorbic acid

  • Formulations: Tablets, chewables, IV injections, effervescent powders

  • Examples:

    • Ascorbic acid tablets 500 mg

    • IV Vitamin C 500 mg/5 mL

Clinical Uses of Vitamin Supplements

  1. Prevention and Treatment of Deficiency Disorders

    • Rickets: Vitamin D

    • Megaloblastic anemia: Vitamin B9 and B12

    • Scurvy: Vitamin C

    • Night blindness: Vitamin A

    • Beriberi and Wernicke’s encephalopathy: Vitamin B1

  2. Supportive Therapy in Chronic Illnesses

    • Chronic kidney disease: B-complex and Vitamin D

    • Cardiovascular risk reduction: Niacin (lipid-lowering effect)

    • Pregnancy and lactation: Folic acid, Vitamin D, B12

  3. Dermatological and Hair Health

    • Biotin for hair loss and brittle nails

    • Vitamin A for acne and psoriasis (topical)

  4. Neurological Disorders

    • Peripheral neuropathy: Vitamin B6 and B12

    • Cognitive decline: B vitamins, Vitamin E (investigational)

  5. Immunity and Antioxidant Defense

    • Vitamin C, E, and A in immune modulation and oxidative stress

    • COVID-19 adjunctive therapy (controversial but under study)

Contraindications and Precautions

  • Fat-soluble vitamins (A, D, E, K): Risk of hypervitaminosis due to accumulation

  • Vitamin A: Teratogenic in high doses during pregnancy

  • Vitamin E: High doses may increase hemorrhagic stroke risk

  • Vitamin B6: Neurotoxicity at megadoses (>200 mg/day chronically)

  • Vitamin D: Hypercalcemia risk in over-supplementation

  • Vitamin K: May interfere with anticoagulants like warfarin

Drug Interactions

  • Vitamin K + Warfarin: Antagonizes anticoagulant effect

  • Vitamin B6 + Levodopa (without carbidopa): Reduces efficacy of levodopa

  • Vitamin C + Iron supplements: Enhances iron absorption

  • Niacin + Statins: Increases risk of myopathy

  • Folic Acid + Methotrexate: Reduces efficacy of methotrexate

  • Vitamin E + Anticoagulants: Additive bleeding risk

  • Vitamin D + Thiazides: Increased risk of hypercalcemia

Special Populations

  • Pregnancy: Folic acid is essential (400–800 mcg/day), avoid high-dose Vitamin A

  • Elderly: Increased need for Vitamin D, B12 (due to poor absorption)

  • Vegans: Risk of B12 deficiency, may require supplementation

  • Malabsorption Syndromes (e.g., Crohn’s, celiac): Multiple vitamin deficiencies

  • Alcoholics: Deficiencies in B1, B6, B9, and B12



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