Systemic Retinoids

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Systemic Retinoids - Vitamin A Power

  • Definition: Synthetic derivatives of Vitamin A (retinol).
  • Generations:
    • 1st Gen (Non-aromatic): Isotretinoin, Alitretinoin.
    • 2nd Gen (Mono-aromatic): Acitretin (from Etretinate).
    • 3rd Gen (Poly-aromatic): Bexarotene, Tazarotene (receptor-selective).
  • Mechanism of Action (MOA):
    • Enter cell → bind nuclear receptors (RARs & RXRs).
    • Complex binds DNA (Retinoic Acid Response Elements - RAREs).
    • Modulates gene expression, affecting key cellular processes:
      • Cell differentiation & proliferation (normalizes epidermal).
      • Apoptosis (induces, e.g., in sebocytes).
      • Sebum production (↓ markedly).
      • Inflammation (↓ via cytokine modulation). Isotretinoin Mechanism and Side Effects

    ⭐ Systemic retinoids exert their effects by binding to two families of nuclear receptors: retinoic acid receptors (RARs: α, β, γ) and retinoid X receptors (RXRs: α, β, γ).

Meet the Retinoids - Acne & Psoriasis Busters

Systemic retinoids are vitamin A derivatives crucial for treating various dermatological conditions by modulating epithelial cell differentiation, proliferation, and inflammation.

DrugGenIndic.Metab.CounselDose Example
Isotretinoin1stSevere acne, Neuroblastoma~20hHepaticTeratogenic (iPLEDGE), Dryness, ↑LFTs/LipidsAcne: 0.5-1 mg/kg/day
Acitretin2ndPsoriasis, Darier's~50h (Etretinate ~120d)Hepatic, ⚠️EtOH→EtretinateTeratogenic, ⚠️Avoid EtOH (during & 2mo post), HepatotoxicPsoriasis: 0.25-0.75 mg/kg/day
Alitretinoin3rdChronic hand eczema~2-10hHepatic (CYP3A4)Teratogenic, Photosensitive, HeadacheEczema: 10-30 mg/day
Bexarotene3rd (RXR)CTCL~7hHepatic (CYP3A4)Teratogenic, ↑Lipids, HypothyroidCTCL: 300 mg/m²/day

Retinoid Reactions - Handle With Care

Systemic retinoids, while effective, are associated with a wide range of dose-dependent adverse effects requiring diligent patient monitoring and management.

Timeline of Systemic Retinoid Side Effects

Key Adverse Reactions:

  • Mucocutaneous: Cheilitis (most common), dry skin, dry eyes, epistaxis.
  • Musculoskeletal: Myalgia, arthralgia, hyperostosis (especially with long-term, high-dose therapy).
  • CNS: Headache, pseudotumor cerebri (benign intracranial hypertension), mood changes, depression.
  • Lab Abnormalities: ↑ Triglycerides, ↑ Cholesterol, ↑ LFTs (liver function tests), ↓ TSH (thyroid-stimulating hormone).
    • Discontinue if LFTs > 3x ULN (upper limit of normal) or triglycerides > 800 mg/dL.

📌 Mnemonic: 'DRY SKIN & LIPs' (Dryness, Raised LFTs/Lipids, Yearning for no pregnancy, Skin fragility, Kerapathy, Intracranial pressure, Night vision issues, Light sensitivity, Itching, Psychiatric issues, Pseudotumor cerebri).

Monitoring Protocol:

⭐ Pseudotumor cerebri (benign intracranial hypertension) is a serious neurological side effect, especially if co-administered with tetracyclines. Concomitant use is contraindicated.

Danger Zone - Pregnancy & Precautions

⚠️ Absolute Teratogenicity! All systemic retinoids.

  • Malformations: Craniofacial, cardiac, CNS, thymic.
  • Pregnancy Prevention Program (PPP) mandatory (India: based on iPLEDGE principles):
    • Two effective contraception forms.
    • Monthly pregnancy tests.
  • Contraception Duration:
    • Isotretinoin/Alitretinoin: 1M pre, during, 1M post.
    • Acitretin: 1M pre, during, 3Y post. ⚠️ Examples of Teratogens
  • Contraindications: Pregnancy, lactation, hypersensitivity, severe liver/kidney disease, hypervitaminosis A, uncontrolled hyperlipidemia.
  • Drug Interactions:
    • Tetracyclines: ↑ pseudotumor cerebri.
    • Vitamin A supplements: ↑ toxicity.
    • Methotrexate + Acitretin: ↑ hepatotoxicity.
    • Progestin-only pills: Unreliable contraception.

⭐📌 S.T.O.P. (PPP): Strict contraception, Testing (pregnancy), Overseeing MD, Patient education.

High‑Yield Points - ⚡ Biggest Takeaways

  • Mechanism: Bind RARs/RXRs (nuclear receptors), alter gene expression for cell differentiation.
  • Teratogenicity: Absolute contraindication in pregnancy; strict contraception mandatory.
  • Indications: Isotretinoin (severe acne); Acitretin (psoriasis, ichthyosis); Bexarotene (CTCL).
  • Side Effects: Mucocutaneous dryness (cheilitis), hyperlipidemia (↑TG), ↑LFTs, photosensitivity.
  • Monitoring: Baseline & periodic LFTs, fasting lipids, pregnancy tests.
  • Interactions: Avoid tetracyclines (↑ICP risk), Vitamin A (toxicity), methotrexate (↑hepatotoxicity).
  • Acitretin: Avoid alcohol during & 2 months post-therapy (forms etretinate, ↑teratogenic risk).

Practice Questions: Systemic Retinoids

Test your understanding with these related questions

A 19-year-old woman presents to the dermatology clinic for a follow-up of worsening acne. She has previously tried topical tretinoin as well as topical and oral antibiotics with no improvement. She recently moved to the area for college and says the acne has caused significant emotional distress when it comes to making new friends. She has no significant past medical or surgical history. Family and social history are also noncontributory. The patient’s blood pressure is 118/77 mm Hg, the pulse is 76/min, the respiratory rate is 17/min, and the temperature is 36.6°C (97.9°F). Physical examination reveals erythematous skin lesions including both open and closed comedones with inflammatory lesions overlying her face, neck, and upper back. The patient asks about oral isotretinoin. Which of the following is the most important step in counseling this patient prior to prescribing oral isotretinoin?

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Flashcards: Systemic Retinoids

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Second line rx for oral lichen planus is _____ ointment, and oral prednisolone

TAP TO REVEAL ANSWER

Second line rx for oral lichen planus is _____ ointment, and oral prednisolone

retinoid

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