VITAMIN A

VITAMIN a
(vye'ta-min)
Aquasol A, Del-Vi-A
Classifications: vitamin;
Therapeutic: vitamin a replacement

Pregnancy Category: a (X if >RDA)

Availability

5000 IU tablets 10,000 IU, 15,000 IU, 25,000 IU capsules; 50,000 IU/mL injection

Action

Vitamin A, a fat-soluble vitamin, acts as a cofactor in mucopolysaccharide synthesis, cholesterol synthesis, and the metabolism of hydroxysteroids.

Therapeutic Effect

Essential for normal growth and development of bones and teeth, for integrity of epithelial and mucosal surfaces, and for synthesis of visual purple necessary for visual adaptation to the dark. Has antioxidant properties.

Uses

Vitamin A deficiency and as dietary supplement during periods of increased requirements, such as pregnancy, lactation, infancy, and infections. Used as replacement therapy in conditions that affect absorption, mobilization, or storage of vitamin A (e.g., steatorrhea, severe biliary obstruction, liver cirrhosis, total gastrectomy). Used in skin disorders [e.g., folliculosis keratosis (Darier's disease), psoriasis]; however, other retinoids are being preferentially selected. Also used as a screening test for fat malabsorption.

Contraindications

History of sensitivity to vitamin A or to any ingredient in formulation, hypervitaminosis A, oral administration to patients with malabsorption syndrome. Safe use in amounts exceeding 6000 IU during pregnancy [category a (category X if >RDA)] is not established.

Cautious Use

Pregnancy (category A at RDA value); women on oral contraceptives, children, hepatic disease, hepatic dysfunction, hepatitis; low-birth-weight infants; renal disease; lactation.

Route & Dosage

Severe Deficiency
Adult: PO 500,000 IU/d for 3 d followed by 50,000 IU/d for 2 wk, then 10,000–20,000 IU/d for 2 mo IM 100,000 IU/d for 3 d followed by 50,000 IU/d for 2 wk
Child: PO/IM <1 y, 10,000 IU/kg/d for 3 d followed by 7500–15,000 IU/d for 10 d; 1–8 y, 10,000 IU/kg/d for 3 d followed by 17,000–35,000 IU/d for 2 wk; >8 y, same as for adult

Dietary Supplement
Child: PO <4 y, 10,000 IU/d; 4–8 y, 15,000 IU/d

Administration

Oral
  • Give on an empty stomach or following food or milk if GI upset occurs.
  • Store in tight, light-resistant containers.

Adverse Effects (≥1%)

CNS: Irritability, headache, intracranial hypertension (pseudotumor cerebri), increased intracranial pressure, bulging fontanelles, papilledema, exophthalmos, miosis, nystagmus. Metabolic: Hypervitaminosis A syndrome (malaise, lethargy, abdominal discomfort, anorexia, vomiting), hypercalcemia. Musculoskeletal: Slow growth; deep, tender, hard lumps (subperiosteal thickening) over radius, tibia, occiput; migratory arthralgia; retarded growth; premature closure of epiphyses. Skin: Gingivitis, lip fissures, excessive sweating, drying or cracking of skin, pruritus, increase in skin pigmentation, massive desquamation, brittle nails, alopecia. Urogenital: Hypomenorrhea. GI: Hepatosplenomegaly, jaundice. Endocrine: Polydipsia, polyurea. Hematologic: Leukopenia, hypoplastic anemias, vitamin A plasma levels >1200 IU/dL, elevations of sedimentation rate and prothrombin time. Body as a Whole: Anaphylaxis, death (after IV use).

Diagnostic Test Interference

Vitamin A may falsely increase serum cholesterol determinations (Zlatkis-Zak reaction); may falsely elevate bilirubin determination (with Ehrlich's reagent).

Interactions

Drug: Mineral oil, cholestyramine may decrease absorption of vitamin A.

Pharmacokinetics

Absorption: Readily absorbed from GI tract in presence of bile salts, pancreatic lipase, and dietary fat. Distribution: Stored mainly in liver; small amounts also found in kidney and body fat; distributed into breast milk. Metabolism: In liver. Elimination: In feces and urine.

Nursing Implications

Assessment & Drug Effects

  • Evaluate dosage with consideration of patient's average daily intake of vitamin A. Take dietary and drug history (e.g., intake of fortified foods, dietary supplements, self-administration or prescription drug sources). Women taking oral contraceptives tend to have significantly high plasma vitamin A levels.
  • Monitor therapeutic effectiveness. Vitamin A deficiency is often associated with protein malnutrition as well as other vitamin deficiencies. It may manifest as night blindness, restriction of growth and development, epithelial alterations, susceptibility to infection, abnormal dryness of skin, mouth, and eyes (xerophthalmia) progressing to keratomalacia (ulceration and necrosis of cornea and conjunctiva), and urinary tract calculi.

Patient & Family Education

  • Avoid use of mineral oil while on vitamin a therapy.
  • Notify physician of symptoms of overdosage (e.g., nausea, vomiting, anorexia, drying and cracking of skin or lips, headache, loss of hair).

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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