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Bupivacaine (Marcain)

Overview

Field Detail
Drug class Amide local anaesthetic
Stock vial 50 mg/20 mL (2.5 mg/mL) or 0.25% solution
Reconstituted conc. N/A (Ready to use)
Storage Room temp; Do not freeze

Preparation

Before you start

Ensure the vial contains Bupivacaine 0.25% (2.5 mg/mL). Check if it contains adrenaline (epinephrine) — for allergy testing, plain Bupivacaine is preferred.

Equipment needed

  • 1 × Bupivacaine 2.5 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 (2.5 mg/mL — neat)

  1. Draw up 0.5–1 mL of the stock (2.5 mg/mL) into a 1 mL syringe.
  2. Label: "Bupivacaine SPT 2.5 mg/mL".

Step 2 — Prepare IDT dilutions

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

  1. IDT 0.0025 mg/mL (1:1,000):

    • A: Draw 0.1 mL of stock (2.5 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.25 mg/mL — 1:10).
    • B: Draw 0.1 mL of A (0.25 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.025 mg/mL — 1:100).
    • C: Draw 0.1 mL of B (0.025 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.0025 mg/mL — 1:1,000).
    • Label: "Bupivacaine IDT 0.0025 mg/mL".

  2. IDT 0.025 mg/mL (1:100):

    • Draw 0.1 mL of syringe B (0.025 mg/mL) into a new 1 mL syringe.
    • Label: "Bupivacaine IDT 0.025 mg/mL".

  3. IDT 0.25 mg/mL (1:10):

    • Draw 0.1 mL of syringe A (0.25 mg/mL) into a new 1 mL syringe.
    • Label: "Bupivacaine IDT 0.25 mg/mL".

  4. IDT 2.5 mg/mL (Neat):

    • Draw up a fresh 0.5 mL of stock (2.5 mg/mL) into a 1 mL syringe.
    • Label: "Bupivacaine IDT 2.5 mg/mL — Neat".

Skin prick test (SPT)

Reagent Concentration
Test solution Neat (2.5 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 0.0025 mg/mL 0.1 mL of 0.025 mg/mL + 0.9 mL NS
2 1:100 0.025 mg/mL 0.1 mL of 0.25 mg/mL + 0.9 mL NS
3 1:10 0.25 mg/mL 0.1 mL neat + 0.9 mL NS
4 Neat 2.5 mg/mL Undiluted stock

Inject: 0.05 mL intradermal. Read at 15–20 minutes.