ASTENIA

Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response.

Dietary vitamin

A is derived from a variety of carotenoids found in plants.

It is enriched in the liver, egg yolks, and the fat component of dairy products.

For the treatment of vitamin

A deficiency.

Vitamin A is effective for the treatment of Vitamin A deficiency.

A refers to a group of fat-soluble substances that are structurally related to and possess the biological activity of the parent substance of the group called all.

• trans retinol or retinol.

A plays vital roles in vision, epithelial differentiation, growth, reproduction, pattern formation during embryogenesis, bone development, hematopoiesis and brain development.

It is also important for the maintenance of the proper functioning of the immune system.

A (all - trans retinol) is converted in the retina to the 11.

• cis -isomer of retinaldehyde or 11.

• cis -retinal. 11.

• cis -retinal functions in the retina in the transduction of light into the neural signals necessary for vision. 11.

• cis -retinal, while attached to opsin in rhodopsin is isomerized to all.

• trans -retinal by light.

This is the event that triggers the nerve impulse to the brain which allows for the perception of light.

• trans -retinal is then released from opsin and reduced to all.

• trans -retinol.

• trans -retinol is isomerized to 11.

• cis -retinol in the dark, and then oxidized to 11.

• cis -retinal recombines with opsin to re-form rhodopsin.

Night blindness or defective vision at low illumination results from a failure to re-synthesize 11.

• cis retinal rapidly.

Epithelial differentiation

The role of Vitamin A in epithelial differentiation, as well as in other physiological processes, involves the binding of Vitamin A to two families of nuclear retinoid receptors (retinoic acid receptors, RARs; and retinoid-X receptors, RXRs).

These receptors function as ligand-activated transcription factors that modulate gene transcription.

When there is not enough Vitamin

A to bind these receptors, natural cell differentiation and growth are interrupted.

Target Actions Organism U Retinoic acid receptor RXR-gamma binder Humans U Apolipoprotein D ligand Humans U Prostaglandin-H2 D-isomerase ligand Humans U Retinol dehydrogenase 12 substrate Humans U Retinol dehydrogenase 5 substrate Humans U Retinol dehydrogenase 13 substrate Humans U Retinal dehydrogenase 2 substrate Humans U Aldehyde dehydrogenase 1A1 substrate Humans U Lecithin retinol acyltransferase substrate Humans U Short-chain dehydrogenase/reductase 3 substrate Humans U Retinaldehyde dehydrogenase 3 substrate Humans U All-trans-retinol 13,14-reductase substrate Humans U Retinol dehydrogenase 11 substrate Humans U Dehydrogenase/reductase SDR family member 4 substrate Humans U Retinol dehydrogenase 14 substrate Humans U Retinol dehydrogenase 8 substrate Humans.

Retinol is conjugated with glucuronic acid; the B-glucuronide undergoes enterohepatic circulation and oxidation to retinol and retinoic acid.

Retinoic acid undergoes decarboxylation and conjugation with glucuronic acid.

Hover over products below to view reaction partners Vitamin A All-trans-retinal.

Improve decision support & research outcomes With structured adverse effects data, including: blackbox warnings, adverse reactions, warning & precautions, & incidence rates.

View sample adverse effects data in our new Data Library! See the data Improve decision support & research outcomes with our structured adverse effects data.

Acute toxicity to vitamin

A can occur when adults or children ingest >100x or >20x the RDA, respectively, over a period of hours or a few days.

The RDA for vitamin

A differs depending on age and sex and can range from 300-900 μg retinol activity equivalents (RAE) per day.

Symptoms of acute systemic toxicity generally include mucocutaneous involvement (e.g. xerosis, cheilitis, skin peeling) and may involve mental status changes.

Children are typically more susceptible to acute vitamin A toxicity.

• daily intakes of as little as 1500 IU/kg have been observed to result in toxicity.

Chronic vitamin

A toxicity can develop following the long-term ingestion of high vitamin A doses.

While there is a wide variation in the lowest toxic vitamin A dose, the ingestion of >25 000 IU daily for 6 years or 100,000 IU daily for 6 months is considered to be toxic.

A toxicity can affect many organ systems and can lead to the development of osteoporosis and CNS effects (e.g. headaches).

For external use only.

􀁑􀀃Adults: when practical, cleanse the affected area by patting or blotting with an appropriate cleansing wipe. 􀁑􀀃Gently dry by patting or blotting with a tissue or a soft cloth before applying cream. 􀁑􀀃When first opening the tube, puncture foil seal with top end of cap. 􀁑􀀃Apply externally or in the lower portion of the anal canal only. 􀁑􀀃Apply to the affected area up to 4 times daily, especially at night, in the morning or after each bowel movement. 􀁑􀀃For application in the lower anal canal: remove cover from dispensing cap.

Attach dispensing cap to tube.

Lubricate dispensing well, then gently insert dispensing cap partway into the anus.

Thoroughly cleanse dispensing cap after each use and replace cover. 􀁑􀀃Children under 12 years of age: ask a doctor.