Lignocaine (Lidocaine)¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | Amide local anaesthetic |
| Stock vial | 50 mg/5 mL (10 mg/mL) or 100 mg/10 mL (10 mg/mL) |
| Reconstituted conc. | N/A (Ready to use) |
| Storage | Room temp; Do not freeze |
Preparation¶
Before you start
Ensure the vial contains Lignocaine 1% (10 mg/mL). Check if it contains adrenaline (epinephrine) — for allergy testing, plain Lignocaine is preferred.
Equipment needed¶
- 1 × Lignocaine 10 mg/mL vial (Plain)
- Normal saline (NS) — for IDT dilutions
- 1 mL syringes × 5 (for test doses/dilutions)
- 25 G needles
Step 1 — Prepare the SPT solution (10 mg/mL — neat)¶
- Draw up 0.5–1 mL of the stock (10 mg/mL) into a 1 mL syringe.
- Label: "Lignocaine SPT 10 mg/mL".
Step 2 — Prepare IDT dilutions¶
Prepare in this order, using a fresh syringe for each step.
-
IDT 0.01 mg/mL (1:1,000):
- A: Draw 0.1 mL of stock (10 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 1 mg/mL — 1:10).
- B: Draw 0.1 mL of A (1 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.1 mg/mL — 1:100).
- C: Draw 0.1 mL of B (0.1 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.01 mg/mL — 1:1,000).
- Label: "Lignocaine IDT 0.01 mg/mL".
-
IDT 0.1 mg/mL (1:100):
- Draw 0.1 mL of syringe B (0.1 mg/mL) into a new 1 mL syringe. (Already prepared in process above).
- Label: "Lignocaine IDT 0.1 mg/mL".
-
IDT 1 mg/mL (1:10):
- Draw 0.1 mL of syringe A (1 mg/mL) into a new 1 mL syringe.
- Label: "Lignocaine IDT 1 mg/mL".
-
IDT 10 mg/mL (Neat):
- Draw up a fresh 0.5 mL of stock (10 mg/mL) into a 1 mL syringe.
- Label: "Lignocaine IDT 10 mg/mL — Neat".
Skin prick test (SPT)¶
| Reagent | Concentration |
|---|---|
| Test solution | Neat (10 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 | 0.01 mg/mL | 0.1 mL of 0.1 mg/mL + 0.9 mL NS |
| 2 | 1:100 | 0.1 mg/mL | 0.1 mL of 1 mg/mL + 0.9 mL NS |
| 3 | 1:10 | 1 mg/mL | 0.1 mL neat + 0.9 mL NS |
| 4 | Neat | 10 mg/mL | Undiluted stock |
Inject: 0.05 mL intradermal. Read at 15–20 minutes.