VITAMIN A PALMITATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VITAMIN A PALMITATE (VITAMIN A PALMITATE).
Vitamin A palmitate is a retinoid that binds to retinoic acid receptors (RARs) and retinoid X receptors (RXRs), modulating gene transcription involved in cell growth, differentiation, and vision. It is converted to retinol and then to retinaldehyde and retinoic acid, essential for phototransduction, epithelial integrity, and immune function.
| Metabolism | Metabolized primarily in the liver to retinyl esters, which are hydrolyzed to retinol. Retinol is oxidized to retinaldehyde and retinoic acid via alcohol dehydrogenases and retinaldehyde dehydrogenases. Further conjugation with glucuronic acid and excretion in bile and urine. |
| Excretion | Primarily hepatobiliary; >90% of retinol esters and metabolites excreted in feces via bile; less than 10% renally eliminated as water-soluble metabolites (e.g., retinoic acid glucuronides). |
| Half-life | Terminal elimination half-life is approximately 7–14 days for retinol in the liver; clinical effects persist for weeks due to extensive hepatic storage. |
| Protein binding | Retinol bound to retinol-binding protein (RBP) and transthyretin (TTR); >95% bound in plasma. |
| Volume of Distribution | Apparent Vd: 0.7–1.3 L/kg, indicating extensive distribution into tissues, especially liver, adipose, and retina. |
| Bioavailability | Oral: 70–90% (dietary fat enhances absorption; bile salts required). IM: ~100%. |
| Onset of Action | Oral: Onset of clinical effect for deficiency correction is 1–2 weeks; for dermatological effects (e.g., acne) 4–8 weeks. IM: Onset similar to oral due to storage. Topical: Not applicable for palmitate; systemic effects require absorption. |
| Duration of Action | Duration: Up to 3–4 months after single high-dose oral or IM administration, due to slow release from hepatic stores and low clearance. |
Adult: 1,500-3,000 IU (450-900 mcg RAE) orally once daily for vitamin A deficiency; IM administration not recommended due to local toxicity.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for renal impairment; monitor serum retinol levels in dialysis patients. |
| Liver impairment | Child-Pugh Class C: reduce dose by 50% due to impaired conversion to retinol; monitor for toxicity. |
| Pediatric use | Infants and children: 1,500-2,500 IU (450-750 mcg RAE) orally once daily; for deficiency, 5,000-10,000 IU/kg/day for 5 days, then 5,000 IU/day. |
| Geriatric use | No specific dose adjustment; monitor for hypervitaminosis A due to potential reduced clearance and increased bone fragility. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for VITAMIN A PALMITATE (VITAMIN A PALMITATE).
| Breastfeeding | Breastfeeding is safe at recommended dietary allowance (1300 mcg RAE/day). M/P ratio not established; human milk content reflects maternal intake. High doses may cause toxicity in infant; avoid supraphysiologic doses. |
| Teratogenic Risk | Vitamin A palmitate is teratogenic at high doses. In the first trimester, doses >10,000 IU/day increase risk of CNS, cardiovascular, and craniofacial malformations. Second and third trimester: high doses may impair fetal growth and hepatic function. The US RDA for pregnancy is 770 mcg RAE/day (2565 IU), and toxicity is dose-dependent. Avoid doses exceeding the RDA unless treating deficiency. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to vitamin A or any component","Hypervitaminosis A","Severe hepatic impairment (relative)","Pregnancy (high doses > 10,000 IU/day)"]
| Precautions | ["Hypervitaminosis A: acute and chronic toxicity (hepatotoxicity, pseudotumor cerebri, teratogenicity)","Hepatotoxicity: monitor liver enzymes in long-term use","Teratogenicity: avoid in pregnancy (high doses)","Bone toxicity: long-term high doses may cause osteoporosis or hyperostosis","Renal impairment: use with caution in patients with renal disease","Hypersensitivity reactions"] |
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| Fetal Monitoring | Monitor serum retinol levels if high-dose therapy required; assess for signs of hypervitaminosis A (headache, blurred vision, hepatotoxicity). Fetal ultrasound if inadvertent high-dose exposure. |
| Fertility Effects | No adverse effects on fertility at physiologic doses. High doses may disrupt menstrual cycles and impair fertility via vitamin A toxicity. |