Vitamin A

• Prevention and Treatment of Vitamin A Deficiency: Used to correct and prevent deficiency states caused by inadequate dietary intake, malabsorption, or increased physiological needs.
• Xerophthalmia and Night Blindness: Treatment and prevention of eye disorders due to vitamin A deficiency, including dryness of the conjunctiva and cornea, and impaired night vision.
• Adjunct Therapy in Measles: Used to reduce complications and mortality in children with measles, particularly in regions with endemic vitamin A deficiency.
• Skin Disorders: Topical and systemic use of vitamin A derivatives for acne vulgaris, psoriasis, and disorders of keratinization.
• Support of Immune Function: Enhances immune response in deficient individuals.

• Route: Oral (capsules, tablets, liquids), topical (creams, gels for dermatologic uses).
• Adults:
• Prevention/Treatment of Deficiency:
  Typically 5,000 to 10,000 IU daily. For severe deficiency or xerophthalmia, higher doses (up to 200,000 IU) may be administered under medical supervision.
• Measles (children):
  50,000 IU for infants 6–12 months, 100,000 IU for children over 1 year, administered once daily for 2 consecutive days.
• Pediatrics: Doses adjusted by age and weight; high-dose supplementation recommended in deficiency or measles.
• Elderly: Same as adults; monitor for toxicity.
• Special Populations (Renal/Hepatic impairment): Use with caution; no specific dose adjustments established.
• Administration Notes:
  Should be taken with meals containing fat to enhance absorption.

Vitamin A is a fat-soluble vitamin essential for vision, immune function, and cellular growth. It is metabolized to retinal, which forms rhodopsin in retinal photoreceptors for low-light vision, and retinoic acid, which regulates gene expression by activating nuclear retinoic acid receptors (RARs and RXRs). These actions promote differentiation and maintenance of epithelial tissues, support hematopoiesis, and modulate immune responses, collectively contributing to its therapeutic effects.

• Absorption: Efficiently absorbed from the small intestine in the presence of dietary fats and bile.
• Distribution: Stored primarily in the liver, which serves as the main reservoir.
• Metabolism: Converted in the liver and target tissues to active metabolites (retinal and retinoic acid).
• Elimination: Metabolites excreted via urine and bile.
• Half-life: Long biological half-life due to liver storage; plasma retinol half-life approximately 10 to 20 hours.

• Pregnancy: No official FDA category; however, high doses (>10,000 IU/day) are teratogenic and contraindicated. Adequate dietary intake is safe and necessary.
• Lactation: Vitamin A passes into breast milk in small amounts and is essential for infant development. High-dose supplementation should be avoided unless prescribed.
• Recommendation: Use the lowest effective dose during pregnancy and lactation.

• Primary Class: Fat-soluble vitamin.
• Subclass: Retinoid.
• Pharmacologic Category: Essential nutrient and antioxidant.

• Known hypersensitivity to vitamin A or excipients.
• Hypervitaminosis A or evidence of vitamin A toxicity.
• Pregnancy at doses exceeding recommended dietary intake.
• Severe liver disease.
• Concurrent use of other vitamin A derivatives at high doses.

• Risk of toxicity with chronic excessive intake causing hepatotoxicity, increased intracranial pressure, and teratogenicity.
• Avoid high-dose vitamin A during pregnancy to prevent fetal malformations.
• Use cautiously in liver disease due to hepatic metabolism and storage.
• Monitor bone health in long-term high-dose use due to increased fracture risk.
• Watch for allergic reactions and discontinue if they occur.

• Common: Headache, nausea, dizziness, dry skin.
• Serious/Rare:
  Hypervitaminosis A presenting with vomiting, blurred vision, hepatotoxicity, intracranial hypertension, bone pain, and teratogenic effects.
• Timing: Side effects typically occur with chronic overdose rather than normal dosing.

• Decreased absorption with orlistat, cholestyramine, mineral oil.
• Increased anticoagulant effect with warfarin.
• Possible antagonism with high-dose vitamin E.
• Interactions with retinoid derivatives may increase toxicity.
• Avoid alcohol which may worsen liver toxicity.

• WHO recommends vitamin A supplementation in children at risk for deficiency to reduce morbidity and mortality from infectious diseases.
• FDA warnings about teratogenicity with high-dose vitamin A supplementation during pregnancy.
• Updated clinical guidelines emphasize monitoring vitamin A levels in malnourished populations and limiting supplementation to recommended doses.

• Store at 15°C to 30°C (59°F to 86°F).
• Protect from moisture, heat, and light.
• Keep container tightly closed.
• No refrigeration needed.
• Keep out of reach of children.