vitamin a

Absorption: GI absorption requires bile acids, fat, lipase, and protein. Aqueous preparations are absorbed more readily than emulsions.

Distribution: Stored primarily in the liver (2-yr supply); small amounts stored in kidneys and lungs. Does not cross the placenta but enters breast milk.

Metabolism/Excretion: Mostly metabolized by the liver.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO	unknown	unknown	unknown
IM	unknown	unknown	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypervitaminosis A;
Malabsorption (oral products);
Hypersensitivity to ingredients in preparations (chlorobutanol, polysorbate 80, butylated hydroxyanisole, butylated hydroxytoluene).

Use Cautiously in:

Severe renal impairment;
OB: Pregnancy (avoid amounts greater than RDA);
Lactation: Lactation (supplements to infant necessary).

Adv. Reactions/Side Effects ⬆ ⬇

Misc: hypervitaminosis A syndrome

Interactions ⬆ ⬇

Drug-drug:

Cholestyramine, colestipol, and mineral oil↓ absorption of vitamin A.
Oral contraceptives↑ levels and the risk of toxicity.

Route/Dosage ⬆ ⬇

RE = retinol equivalents. Doses should be individualized on the basis of degree of deficiency. RDA: Adult males 1000 mcg RE; adult females 800 mcg RE

Kwashiorkor

IM (Children ): 30 mg followed by oral dosing.
PO (Adults and Children >8 yr): 10,000–20,000 units/day for ≥2 mo.
PO (Children <8 yr): 5,000–10,000 units/day for ≥2 mo.

Xerophthalmia

PO IM (Children ): 110 mg/day PO as retinyl palmitate or 55 mg IM; then 110 mg PO/day given with vitamin E to improve effectiveness.

Parenteral dosing

IM (Adults ): 100,000 units/day for 3 days; then 50,000 units/day for 2 wk with additional follow-up oral therapy of 10,000–20,000 units/day.
IM (Children 1–8 yr): 17,500–35,000 units/day for 10 days with additional follow-up oral therapy of 5000–10,000 units/day.
IM (Infants ): 7500–15,000 units/day with additional follow-up oral therapy of 5000–10,000 units/day.

Availability ⬆ ⬇

(Generic available)

Capsules: 3000 RE (10,000 units)^{Rx, OTC}, 7500 RE (25,000 units); 15,000 RE (50,000 units)
Tablets: 3000 RE (10,000 units)^{Rx, OTC}, 7500 RE (25,000 units)^{Rx, OTC}, 15,000 RE (50,000 units)
Oral solution: 1500 RE (5000 units)/0.1 mL
Solution for injection: 50,000 units/mL

Assessment ⬆ ⬇

Assess patient for signs of vitamin A deficiency (night blindness; frequent eye, ear, sinus, and GU infections; dry mucous membranes; rough, scaly skin with goose pimple-like lesions; photophobia; and dry eyes) prior to and periodically throughout therapy.
Assess nutritional status through 24-hr diet recall. Determine frequency of consumption of vitamin A–rich foods.

Lab Test Considerations:

Chronic toxicity may cause increased blood glucose, calcium, BUN, cholesterol, and triglyceride levels.
- Plasma vitamin A and carotene levels may be evaluated prior to therapy to determine vitamin A deficiency.
- With high doses, erythrocyte and leukocyte counts may be decreased, and erythrocyte sedimentation rate and prothrombin time may be increased.

Implementation ⬆ ⬇

PO: Administer with or after meals.
- Solution may be dropped directly into mouth or mixed with cereal, fruit juice, or other food. Use calibrated dropper supplied by manufacturer to measure solution accurately.
IM: Parenteral administration is indicated only when oral administration is not possible (because of malabsorption, NPO status, vomiting, or severe ocular damage).
- Do not administer vitamin A intravenously because of the risk of anaphylactic shock and death.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed. If a dose is missed, it should be omitted, as fat-soluble vitamins are stored in the body for long periods.
Encourage patient to comply with diet recommendations of health care professional. Explain that the best source of vitamins is a well-balanced diet with foods from the four basic food groups.
Foods high in vitamin A include liver, fish liver oils, egg yolks, yellow-orange fruits and vegetables, dark-green leafy vegetables, whole milk, vitamin A–fortified skim milk, butter, and margarine. Ordinary cooking does not destroy vitamin A, but frozen foods lose 5–10% during storage for 12 mo.
Patients self-medicating with vitamin supplements should be cautioned not to exceed RDA. The effectiveness of megadoses for treatment of various medical conditions is unproved, and this may cause side effects and toxicity.
Review symptoms of hypervitaminosis A syndrome (headaches, bulging fontanelles in infants, irritability, yellow-orange discoloration of skin, drying and desquamation of skin and lips, hair loss, anorexia, vomiting, joint and bone pain). Instruct patient to report these symptoms promptly to health care professional.
Advise patient that mineral oil may interfere with the absorption of fat-soluble vitamins and should not be used concurrently.
Emphasize the importance of follow-up exams to evaluate progress. Ophthalmologic exams may be required prior to and periodically throughout therapy.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇