[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Vitamins # Vitamins Essential organic nutrients the body cannot make in enough amounts. Fat-soluble ones (A, D) build up and can be toxic; water-soluble ones leave in the urine. Updated Nov 1, 2026 ## What they are Vitamin products used to prevent or treat deficiency states: vitamin D (colecalciferol, ergocalciferol, calcitriol), vitamin A (retinol), vitamin C (ascorbic acid) and the B vitamins (thiamine, riboflavin, nicotinamide, pyridoxine). ## Mechanism of action Most B vitamins become coenzymes (thiamine pyrophosphate, FAD, NAD, pyridoxal phosphate). Vitamin C is a cofactor for collagen and an antioxidant. Vitamin D works as a hormone through a nuclear receptor, and vitamin A supports vision, epithelia and immunity. Target: Coenzymes, cofactors and the vitamin D nuclear receptor ## Key points - Thiamine goes with IV glucose in people with low reserves; it treats Wernicke encephalopathy and beriberi. - Vitamin D needs liver then kidney activation; in kidney failure calcitriol is used. Toxicity = hypercalcaemia. - Vitamin A: night blindness is the first sign of deficiency; WHO gives it to children under 5 with measles; teratogenic at high doses. - Isoniazid depletes B6 (neuropathy) and can cause pellagra (B3). - Vitamin C deficiency = scurvy: bleeding gums, bruising, poor healing. ## Drugs in this class - [**Colecalciferol** Vitamin D3, the form the skin makes in sunlight. Liver and kidney turn it into the hormone that lets the gut absorb… Vitamin D receptor (VDR), a nuclear receptor](https://durgical.com/en/pharmacology/colecalciferol/) - [**Thiamine** Vitamin B1. Given urgently in Wernicke encephalopathy and beriberi, and with IV glucose to people with low reserves… Thiamine pyrophosphate, coenzyme of pyruvate and α-keto acid decarboxylation](https://durgical.com/en/pharmacology/thiamine/) - [**Ascorbic acid** Vitamin C. Needed to build collagen and absorb plant iron; the body cannot make or store it. Its lack causes scurvy. Cofactor for collagen formation; antioxidant](https://durgical.com/en/pharmacology/ascorbic-acid/) - [**Pyridoxine** Vitamin B6. Prevents the nerve damage of isoniazid and is the antidote in isoniazid poisoning. Too much damages nerves. Pyridoxal 5'-phosphate, coenzyme of transamination and decarboxylation](https://durgical.com/en/pharmacology/pyridoxine/) - [**Retinol** Vitamin A. Prevents night blindness and xerophthalmia, and lowers measles complications in children. High doses in… Visual pigment of the retina and retinoid receptors in epithelia](https://durgical.com/en/pharmacology/retinol/) - [**Calcitriol** The active form of vitamin D (1,25-dihydroxyvitamin D3). It works without kidney activation, so it is used in chronic… Vitamin D receptor (VDR), a nuclear receptor](https://durgical.com/en/pharmacology/calcitriol/) - [**Ergocalciferol** Vitamin D2, made from plants and fungi. Activated like D3; prescribed for hypoparathyroidism and hard-to-treat… Vitamin D receptor (VDR), through its active metabolite](https://durgical.com/en/pharmacology/ergocalciferol/) - [**Nicotinamide** A form of vitamin B3 used to treat pellagra. Unlike nicotinic acid, it does not cause flushing and does not lower… Precursor of NAD and NADP, the coenzymes of oxidation–reduction reactions](https://durgical.com/en/pharmacology/nicotinamide/) - [**Riboflavin** Vitamin B2, the building block of the coenzymes FMN and FAD. Deficiency causes sores at the mouth corners, a sore… Precursor of FMN and FAD, the flavin coenzymes](https://durgical.com/en/pharmacology/riboflavin/) - [**Paricalcitol** A synthetic active vitamin D analogue that lowers parathyroid hormone in chronic kidney disease. Calcium must be… Vitamin D receptor (nuclear receptor) in the parathyroid glands](https://durgical.com/en/pharmacology/paricalcitol/) ## Others in the class - Paricalcitol - Folic acid (antianaemia page) - Vitamin B12 (antianaemia page) - Phytomenadione (vitamin K) ## Test yourself Think of the answer, then tap the question to see it. ## Which vitamins are fat-soluble and therefore can accumulate to toxic levels? A, D, E and K. ## Which vitamin deficiency causes Wernicke encephalopathy? Thiamine (vitamin B1). ## Which vitamin deficiency causes pellagra? Niacin (vitamin B3). [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/classes/vitamins/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) [← All of pharmacology](https://durgical.com/en/pharmacology/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - THIAMINE HYDROCHLORIDE INJECTION, SOLUTION injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=06446e9a-0e85-0623-e063-6294a90ac403) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - ERGOCALCIFEROL capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=87e80b1f-e376-45ba-825b-a6fda4b82325) (DailyMed (U.S. National Library of Medicine), 2026); [Vitamin A: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002400.htm) (MedlinePlus (U.S. National Library of Medicine), 2026); [Pellagra: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000342.htm) (MedlinePlus (U.S. National Library of Medicine), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/classes/vitamins/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/vitamins/