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Dexamethasone

Overview

Field Detail
Drug class Corticosteroid / Glucocorticoid
Stock formulation 4 mg/mL or 8 mg/2 mL (4 mg/mL)
Reconstituted conc. N/A (Ready to use)
Storage Room temp; Protect from light

Preparation

Before you start

Ensure the vial contains 4 mg/mL. Check expiry and integrity.

Equipment needed

  • 1 × Dexamethasone 4 mg/mL vial
  • Normal saline (NS) — for IDT dilutions
  • 1 mL syringes × 2
  • 25 G needles

Step 1 — Prepare the SPT solution (4 mg/mL — neat)

  1. Draw up 0.5–1 mL of the stock (4 mg/mL) into a 1 mL syringe.
  2. Label: "Dexamethasone SPT 4 mg/mL".

Step 2 — Prepare IDT dilutions

Prepare in this order, using a fresh syringe for each step.

  1. IDT 0.04 mg/mL (1:100):
    • Draw 0.1 mL of stock (4 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.4 mg/mL — 1:10).
    • Draw 0.1 mL of this 0.4 mg/mL into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.04 mg/mL — 1:100).
    • Label: "Dexamethasone IDT 0.04 mg/mL".

Skin prick test (SPT)

Reagent Concentration
Test solution Neat (4 mg/mL)
Positive control Histamine 10 mg/mL
Negative control Normal saline

Interpretation: Wheal ≥3 mm vs negative control = positive.

Intradermal test (IDT)

Dilution series

Step Dilution Concentration Preparation
1 1:100 0.04 mg/mL 0.1 mL of 0.4 mg/mL + 0.9 mL NS

Inject: 0.05 mL intradermal. Read at 15–20 minutes. Delayed Reading: If history is suggestive of a delayed reaction, re-read at 24 and 48 hours.