vitamin A

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^[1]^[2]^[3]^[4]^[5]

Dosage

adults & children > 10 years: 5000 IU
children 7-10 years: 3300-3500 IU
children 4-6 years: 2500 IU
children 6 months-3 years: 1500-2000 IU
infants up to 6 months: 1500 IU

1 mg = 3333 units severe deficiency:

100,000 IU/day for 3 days
followed by 50,000 IU daily for 2 weeks
then 10,000-20,000 IU daily for 2 months

Capsule: 25,000 units, 50,000 units

Pharmacokinetics

retinyl esters are storage forms of vitamin A

Adverse effects

not common (1-10%)
- irritability, vertigo, lethargy, malaise, fever, headache, drying or cracking of skin, hypercalcemia, weight loss, visual changes, hypervitaminosis
fracture
- 2-fold increase risk of fractures in postmenopausal women not taking hormone replacement therapy with high intake of vitamin A
- high serum levels of retinol (but not beta-carotene) associated with 1.6 fold increased risk of fracture in 50-75 year old men^[4]

Drug interactions

carbamazepine: increased clearance of carbamazepine
cholestyramine, mineral oil: decreased absorption of vit A
oral contraceptives: increased absorption of vit A
isotretinoin, etretinate: increased toxicity
vitamin A can antagonize the ability of vitamin D to enhance Ca+2 absorption^[3]

More general terms

vitamin

More specific terms

Additional terms

vitamin A deficiency (hyporetinemia)

Component of

References

↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
↑ ^{Jump up to: 3.0} ^3.1 Prescriber's Letter 9(2):8 2002
↑ ^{Jump up to: 4.0} ^4.1 Journal Watch 23(5):42, 2003 Micahaelsson K et al Serum retinol levels and the risk of fracture. N Engl J Med 348:287, 2003 PMID: https://www.ncbi.nlm.nih.gov/pubmed/12540641 Lips P Hypervitaminosis A and fractures. N Engl J Med 348:347, 2003 PMID: https://www.ncbi.nlm.nih.gov/pubmed/12540650
↑ Department of Veterans Affairs, VA National Formulary

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