Lecture Notes: Tretinoin as a Topical Medication

Overview of Tretinoin

• Purpose:
  • Used in the treatment of acne.
  • Also treats facial wrinkles.
• Chemical Nature:
  • Derivative of Vitamin A.
  • Contains four double bonds in the trans configuration.
  • Known as all-trans-retinoic acid.

Mechanism of Action

• Target:
  • Enters inflammatory cells and interacts with DNA in the nucleus.
• Receptors Involved:
  • Binds to RAR (retinoic acid receptor) and activates RXR (retinoid X receptor).
• Process:
  • Forms a heterodimer with RXR.
  • Interacts with DNA at RARE (retinoic acid responsive elements) for gene transcription.
  • Increases protein synthesis.
• Effects:
  • Reduces cornification and acne formation.
  • Promotes epidermal proliferation and cell differentiation.
  • Reduces inflammatory mediators.

Usage and Forms

• Forms Available:
  • As a cream and gel.
  • Gel available in microsphere form for better absorption.
  • Concentrations for cream: 0.02% to 0.1%.
  • Concentrations for gel: 0.04% to 0.1%.
• Application:
  • Applied as a thin film once daily before bedtime.
• Effect:
  • Increases detachment of cornified cells and shedding of keratinocytes.
  • May decrease melanin pigmentation.

Precautions

• Skin Irritation:
  • Can cause local skin irritation, dryness, and redness.
  • Initial application may increase acne severity due to skin reactions.
  • Not recommended for broken, inflamed skin, or people with eczema.
  • Skin should be washed and dried gently (no scrubbing) before application.
  • Use a moisturizer to minimize irritation.
• Phototoxicity:
  • Increases sensitivity to sunlight and UV radiation.
  • Avoid direct sunlight or UV exposure; use sunscreen (SPF > 15).
• Contact Precautions:
  • Avoid contact with eyes, mouth, or vagina.

Side Effects

• Common Side Effects:
  • Skin irritation, dryness, itching, burning, and stinging.
  • Can cause hyper or hypopigmentation.
  • May lead to erythema, nasopharyngitis, and urticaria.

Chemical Structure

• Tretinoin Structure:
  • Nine-carbon carboxylic acid derivative.
  • Four double bonds (nona-2,4,6,8-tetraenoic acid).
  • Methyl groups at third and seventh positions; 9-cyclohexen-1-yl structure.

Summary

• Tretinoin is a topical medication derived from Vitamin A used for acne and wrinkle treatment.
• Available as cream or gel; causes skin irritation managed by precautions.
• Reduces acne by affecting skin cell turnover and pigmentation.

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Note: Always consult with a healthcare provider for proper use and potential risks associated with tretinoin.