1. Clinical Overview
Vitamin C (Ascorbic Acid) is a water-soluble essential vitamin and potent antioxidant. In the Indian context, it is widely used for the prevention and treatment of vitamin C deficiency (scurvy), to support immune function, and to enhance non-heme iron absorption. The 150mg strength is a common prophylactic and therapeutic dose suitable for the Indian population, addressing dietary gaps and increased requirements during stress or illness.
| Onset | Duration | Bioavailability |
|---|---|---|
| Absorption begins within 1-2 hours of oral administration. Tissue saturation and clinical effects (e.g., improvement in scurvy symptoms) may take several days to weeks. | Approximately 24 hours, necessitating daily intake as the body does not store significant amounts. Plasma levels return to baseline within 12-24 hours post-dose if not replenished. | Approximately 70-90% at doses up to 200mg. Bioavailability decreases significantly with single doses exceeding 1g due to saturable active transport in the intestine. |
2. Mechanism of Action
Vitamin C acts as an essential cofactor for multiple enzymatic reactions, including the biosynthesis of collagen, carnitine, and neurotransmitters (norepinephrine). It is a potent water-soluble antioxidant that scavenges reactive oxygen and nitrogen species, thereby protecting cellular components from oxidative damage. It also regenerates other antioxidants like vitamin E. It enhances immune cell function (neutrophils, lymphocytes) and facilitates dietary iron absorption by reducing ferric iron (Fe3+) to the more absorbable ferrous form (Fe2+).
3. Indications & Uses
- Prevention and treatment of Vitamin C deficiency (Scurvy)
- Dietary supplementation in individuals with inadequate dietary intake
4. Dosage & Administration
Adult Dosage: Prophylactic: 70-150mg daily. Therapeutic (Scurvy): 500mg to 1g daily for at least 2 weeks, followed by prophylactic dose.
Administration: Administer orally, preferably with or after meals to reduce gastric irritation. Tablet/Capsule should be swallowed whole with a glass of water. Chewable tablets should be chewed thoroughly. Do not crush sustained-release formulations. Can be taken with iron supplements to enhance absorption.
5. Side Effects
Common side effects may include:
- Nausea
- Abdominal cramps/pain
- Heartburn
- Diarrhea (with high doses >1g)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Oral Iron Supplements (Ferrous sulfate) | Vitamin C enhances iron absorption by maintaining it in ferrous state. | Moderate |
| Aspirin | May increase renal excretion of ascorbic acid and decrease its uptake by leukocytes. | Moderate |
| Fluphenazine, Warfarin | Vitamin C may decrease serum levels/effects of these drugs. | Moderate |
| Aluminum-containing antacids | Vitamin C may increase aluminum absorption, potentially increasing toxicity. | Major |
| Estrogens, Oral Contraceptives | May increase serum vitamin C levels. | Minor |
7. Patient Counselling
- DO take it regularly as advised, preferably with a meal.
- DO inform your doctor if you have a history of kidney stones or iron overload.
- DO store in a cool, dry place away from light and moisture.
- DON'T crush or chew sustained-release tablets unless instructed.
- DON'T take mega-doses (>1g/day) without medical supervision.
8. Toxicology & Storage
Overdose: Acute overdose is unlikely due to excellent water solubility and renal clearance. Symptoms of extremely high intake (>3-4g single dose) include severe diarrhea, nausea, abdominal cramps, flatulence, and insomnia.
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep the container tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.