Methylprednisolone (Solu-Medrol)¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | Corticosteroid / Glucocorticoid |
| Stock formulation | 1 g powder for injection |
| Reconstituted conc. | 20 mg/mL (add 5 mL NS) |
| Storage | Room temp before reconstitution; 2–8°C after |
Preparation¶
Reconstitution
Methylprednisolone is typically reconstituted to 20 mg/mL for skin testing. Ensure the 5 mL of Normal Saline (NS) is added and the solution is clear before use.
Equipment needed¶
- 1 × Methylprednisolone 1 g powder vial
- Normal saline (NS) — for reconstitution and dilutions
- 10 mL syringe
- 1 mL syringes × 4 (for test doses/dilutions)
- 25 G needles
Step 1 — Reconstitute the stock (20 mg/mL)¶
- Add 5 mL of NS to the 1 g powder vial.
- Shake gently until completely dissolved. (This is 200 mg/mL).
- Draw 0.1 mL of this 200 mg/mL solution into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 20 mg/mL).
- Label: "Methylprednisolone SPT 20 mg/mL".
Step 2 — Prepare IDT dilutions¶
Prepare in this order, using a fresh syringe for each step.
-
IDT 2 mg/mL (1:10):
- Draw 0.1 mL of stock (20 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 2 mg/mL — 1:10).
- Label: "Methylprednisolone IDT 2 mg/mL".
-
IDT 0.2 mg/mL (1:100):
- Draw 0.1 mL of the 2 mg/mL syringe into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.2 mg/mL — 1:100).
- Label: "Methylprednisolone IDT 0.2 mg/mL".
Skin prick test (SPT)¶
| Reagent | Concentration |
|---|---|
| Test solution | Neat (20 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 | 0.2 mg/mL | 0.1 mL of 2 mg/mL + 0.9 mL NS |
| 2 | 1:10 | 2 mg/mL | 0.1 mL neat + 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.