Mechanism of action
The action of retinol and its active metabolites is exerted at the genetic level through interaction with specific nuclear receptors. Pharmacology distinguishes two main types of such receptors: RAR (retinoic acid receptors) and RXR (retinoid X receptors). Activation of these receptors triggers the regulation of gene expression by stimulating transcription, which ensures the drug's effect on cell proliferation and differentiation.
Pharmacological effects
The biological role and pharmacodynamics of retinol encompass several key areas:
- Visual function: the substance is necessary for the synthesis of the visual pigment rhodopsin, which ensures normal scotopic vision.
- Effect on the epithelium: the drug takes a direct part in the synthesis of glycoproteins and glycosaminoglycans, ensuring normal functioning, trophism, and regeneration of the epithelium of the skin and mucous membranes (exhibits a pronounced antixerophthalmic effect).
- Metabolism: participation in oxidation-reduction processes and the regulation of lipid metabolism.
Indications for use
According to reference data, retinol is prescribed as part of complex pharmacotherapy for various pathological conditions:
- Replacement therapy: prevention and treatment of hypovitaminosis A and avitaminosis A.
- Ophthalmology: hemeralopia ("chicken blindness") and associated scotopic vision disorders, corneal lesions.
- Dermatology and traumatology: psoriasis, burns, trophic ulcers (to stimulate epithelialization and skin tissue repair).
- Gastroenterology: chronic inflammatory diseases of the gastrointestinal tract (enteritis, enterocolitis).
- Other pathologies: hepatitis, lung diseases.
Side effects and hypervitaminosis
Overdose leads to the presentation of acute poisoning (hypervitaminosis A), affecting various organs and systems:
- CNS: onset of lethargy, drowsiness, severe headache.
- Dyspeptic syndrome: nausea, vomiting.
- Skin and skin appendages: characteristic skin peeling, alopecia (hair loss).
Contraindications for use include individual hypersensitivity and the risk of overdose.
Administration features and pharmacy
The drug is available in various dosage forms for differentiated use:
- Dragees of 0.001 g (3300 IU) and 0.01 g (33000 IU), as well as tablets of 3300 IU (for oral administration).
- Oil solutions for oral administration with varying activity per 1 ml: 100000, 200000, and 250000 IU.
- Oil solution in 0.86% ampoules of 1 ml (25000 IU) and oil solutions for intramuscular injections with a concentration per 1 ml of 25000, 50000, and 100000 IU.
Retinol belongs to the first generation of retinoids, along with its esters (retinyl acetate, retinyl palmitate) and carotene.
Retinol guarding vision: Rhodopsin Regulates scotopic Retinal function via RAR and RXR.
Class and exam questions
What role does retinol play in the visual analyzer?
Retinol is essential for the synthesis of the visual pigment rhodopsin, the deficiency of which leads to a disorder of scotopic vision — hemeralopia ("chicken blindness").
Which receptors mediate the genetic effect of retinoids?
The effect is exerted via specific nuclear receptors of two types: RAR (retinoic acid receptors) and RXR (retinoid X receptors).
What are the symptoms of acute hypervitaminosis A?
Central nervous system disorders are observed (lethargy, headache, drowsiness), dyspepsia (nausea, vomiting), as well as skin peeling and alopecia.
In what dosage forms is retinyl acetate available for injection?
The drug is available as an oil solution in ampoules for intramuscular injections (1 ml contains 25000, 50000, or 100000 IU).
What else to study on this topic
- Classification of retinoids by generations (first, second, and third generations)
- Biochemical transformation of carotenoids (provitamin A) in the body
- Pharmacokinetics of fat-soluble vitamins and the role of hepatic stores
- Interaction of retinol with other fat-soluble vitamins (D, E, K)
- Pathogenesis of dermatological effects of retinoids in psoriasis
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