Subcutaneous Immunotherapy

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SCIT Basics - Needle Power Intro

  • Subcutaneous Immunotherapy (SCIT): Disease-modifying therapy; repeated administration of gradually increasing doses of specific allergen extracts.
  • Goal: Induce clinical tolerance, achieve long-term remission of allergy symptoms.
  • Mechanism:
    • Early: Mast cell/basophil desensitization.
    • Late:
      • Shift: ↓Th2 (pro-allergic), ↑Th1 response.
      • Induces: Regulatory T cells (Tregs) → IL-10, TGF-β.
      • Produces: Allergen-specific IgG4 (blocking Abs).
      • Reduces: Allergen-specific IgE over time.
  • Key Indications:
    • Allergic Rhinitis/Conjunctivitis (mod-severe, persistent).
    • Allergic Asthma (mild-mod, allergen-driven, controlled).
    • Insect Venom Hypersensitivity (systemic reactions). SCIT mechanism of action showing immune cell shifts

⭐ SCIT is the only therapy that alters the natural course of allergic disease, offering potential long-term remission post-discontinuation.

SCIT Regimens - Prickly Protocols

  • Phases of SCIT:
    • Build-up Phase: Gradually ↑ doses of allergen extract. Frequency: 1-2 times/week. Duration: 3-6 months.
    • Maintenance Phase: Constant, highest tolerated dose. Frequency: Every 2-4 weeks, then potentially longer intervals. Duration: 3-5 years.
  • Conventional Protocol: Most common, gradual dose escalation over months.
  • Accelerated Protocols:
    • Cluster: Several injections given on a single day, separated by 20-30 min intervals, weekly/biweekly. Build-up: 4-8 weeks.
    • Rush: Multiple injections over 1-3 days to reach maintenance dose quickly. Higher risk of systemic reactions.
    • Ultra-rush: Maintenance dose reached in 1 day.
  • 📌 Mnemonic: "C-C-R-U" (Conventional, Cluster, Rush, Ultra-rush) for protocol types.

⭐ Rush immunotherapy carries a higher risk of systemic allergic reactions compared to conventional protocols, requiring close monitoring in a specialized setting during administration. This is a frequently tested concept regarding patient safety and protocol selection in SCIT for NEET PG.

  • Dose adjustments: Based on local/systemic reactions, missed doses, new vial of extract.

SCIT Safety - Reaction Rescue

  • Adverse Reactions (ARs):
    • Local ARs: Common; erythema, pruritus, swelling at injection site. Manage: cold compress, oral antihistamines, topical steroids.
    • Systemic ARs (SARs): Less common, potentially life-threatening.
      • Graded by severity (e.g., WAO: Grade 1-Skin/Upper airway; Grade 2-Moderate respiratory/GI; Grade 3-Severe hypoxia/hypotension; Grade 4-Cardiac/Respiratory arrest).
  • Anaphylaxis Management: 📌 EpiPen First!
    • STOP SCIT.
    • IM Epinephrine (1:1000): 0.3-0.5 mg (adults); 0.01 mg/kg (max 0.3 mg) (children). Repeat 5-15 min PRN.
    • Supine, elevate legs.
    • Supplemental Oxygen.
    • IV fluids (NS).
    • Antihistamines (H1 & H2 blockers).
    • Corticosteroids (IV/IM).
    • Bronchodilators for bronchospasm.
    • Monitor vitals. Observe 4-6 hrs (biphasic risk).

    ⭐ Epinephrine is cornerstone of anaphylaxis treatment; administer promptly. Delay linked to fatal outcomes.

![EpiPen 2-Pak: Epinephrine Auto-Injector](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/ENT_Allergy_and_Immunotherapy_Subcutaneous_Immunotherapy/73f49d9b-26af-4b69-97d9-b2c282ef74b9.cfm)
  • Prevention & Precautions:
    • 30-min post-injection observation.
    • Dose adjustment for large local reactions or missed doses.
    • Avoid SCIT during acute illness/fever.

SCIT Outcomes - Allergy Adieu?

  • Clinical Efficacy:
    • Significantly ↓ symptoms & medication for allergic rhinitis (AR), allergic asthma, insect venom hypersensitivity.
    • Prevents new allergen sensitizations.
    • Can halt AR progression to asthma, particularly in children.
  • Treatment Duration & Long-term Benefit:
    • Typical duration: 3-5 years.
    • Long-lasting remission (years) common post-discontinuation.
    • Relapse possible; retreatment can be effective.
  • Key Patient Groups:
    • Children: Highly effective; potential for altering natural disease course.

      ⭐ SCIT is disease-modifying: prevents asthma in AR children & new sensitizations.

    • Pregnancy: Maintenance SCIT generally safe; avoid initiation during pregnancy.
    • Asthmatics: Requires stable, well-controlled asthma (FEV1 > 70% predicted).

High‑Yield Points - ⚡ Biggest Takeaways

  • SCIT promotes immune tolerance: shifts Th2 to Th1, boosts Treg cells and IgG4.
  • Indicated for allergic rhinitis, asthma, and hymenoptera venom allergy.
  • Contraindicated in uncontrolled asthma, with beta-blockers, and active autoimmune disease.
  • Involves build-up phase (dose escalation) and maintenance phase (constant dose).
  • Treatment duration is typically 3-5 years for sustained benefit.
  • Local reactions are common; systemic reactions (e.g., anaphylaxis) are rare but serious.
  • Always have epinephrine ready for potential anaphylaxis_._

Practice Questions: Subcutaneous Immunotherapy

Test your understanding with these related questions

Which of the following regarding the vaccine vial monitor (VVM) is true? 1. It is used for monitoring heat exposure of the vaccine by healthcare workers in primary healthcare. 2. It shows cumulative exposure of the vaccine to the heat. 3. It can be used to assess the potential efficacy of the vaccine 4. Calculation of the expiry date can be done using VVM. 5. The expiry date of the vaccine can be relaxed if VVM is an acceptable range. 6. If the square and the circle are the same in color, then the vaccine can be safely used.

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Flashcards: Subcutaneous Immunotherapy

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Allergic rhinitis can lead to _____ otitis media

TAP TO REVEAL ANSWER

Allergic rhinitis can lead to _____ otitis media

serous

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