Vancomycin¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | Glycopeptide antibiotic |
| Stock vial | 500 mg or 1 g powder for injection |
| Reconstituted conc. | 100 mg/mL (add 5 mL NS to 500 mg or 10 mL NS to 1 g) |
| Storage | Room temp before; 2–8°C after |
Preparation¶
Before you start
Ensure the vial contains 500 mg or 1 g of Vancomycin. Check expiry and integrity. Note that Vancomycin is a potent direct histamine-releaser and must be tested at extremely high dilutions.
Equipment needed¶
- 1 × Vancomycin 500 mg or 1 g vial
- Normal saline (NS) — for all dilutions
- 10 mL syringe (for initial reconstitution)
- 1 mL syringes × 10 (for multiple serial dilutions)
- 25 G needles
Step 1 — Initial Reconstitution (100 mg/mL)¶
- Reconstitute the 500 mg vial with 5 mL NS (or 1 g vial with 10 mL NS).
- Dissolve completely to obtain 100 mg/mL.
- Note: This solution is NOT for testing.
Step 2 — Prepare the SPT solution (100 mg/mL)¶
- Draw up 0.5–1 mL of the neat (100 mg/mL) solution into a 1 mL syringe.
- Label: "Vancomycin SPT 100 mg/mL".
Step 3 — Prepare IDT dilutions (1:1,000,000)¶
Prepare in this order, using a fresh syringe for each step.
- IDT 0.0001 mg/mL (1:1,000,000):
- A: Draw 0.1 mL of stock (100 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 10 mg/mL — 1:10).
- B: Draw 0.1 mL of A (10 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 1 mg/mL — 1:100).
- C: Draw 0.1 mL of B (1 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.1 mg/mL — 1:1,000).
- D: Draw 0.1 mL of C (0.1 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.01 mg/mL — 1:10,000).
- E: Draw 0.1 mL of D (0.01 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.001 mg/mL — 1:100,000).
- F: Draw 0.1 mL of E (0.001 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.0001 mg/mL — 1:1,000,000).
- Label: "Vancomycin IDT 0.0001 mg/mL".
Skin prick test (SPT)¶
| Reagent | Concentration |
|---|---|
| Test solution | Neat (100 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 | 1:1,000,000 | 0.0001 mg/mL | 0.1 mL of 0.001 mg/mL + 0.9 mL NS |
Histamine Release
Vancomycin is a potent direct histamine releaser. Results must be interpreted with extreme caution. IDT should be performed at 1:1,000,000 as per the institutional protocol.
Inject: 0.05 mL intradermal. Read at 15–20 minutes.