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Flucloxacillin

Overview

Field Detail
Drug class Beta-lactam / penicillinase-resistant penicillin
Stock vial 500 mg powder for injection
Reconstituted conc. See Preparation (strict 4-step process)
Storage Room temp before; 2–8°C after

Preparation

Complex Preparation

Flucloxacillin requires a precise 4-step preparation process to reach the correct testing concentrations. Do not use the initial 100 mg/mL solution for testing.

Equipment needed

  • 1 × Flucloxacillin 500 mg vial
  • Normal saline (NS) — for all dilutions
  • 10 mL syringe (for initial reconstitution)
  • 1 mL syringes × 5 (for serial dilutions)
  • 25 G needles

Step-by-step Process

1. Initial Reconstitution (100 mg/mL)

  • Add 4.6 mL NS to the 500 mg vial.
  • Dissolve completely to obtain 100 mg/mL.
  • Note: This solution is NOT for testing.

2. Intermediate Dilution (20 mg/mL)

  • Draw 1.0 mL of the 100 mg/mL solution into a 1 mL or 5 mL syringe.
  • Add 4.0 mL NS. Mix.
  • This results in 20 mg/mL.
  • Note: This solution is NOT for testing.

3. Prepare the IDT "Neat" (2 mg/mL)

  • Draw 0.1 mL of the 20 mg/mL solution into a 1 mL syringe.
  • Add 0.9 mL NS. Mix.
  • This results in 2 mg/mL.
  • Label: "Flucloxacillin IDT 2 mg/mL (Neat)".

4. Prepare the SPT and IDT 1:10 (0.2 mg/mL)

  • Draw 0.1 mL of the 2 mg/mL solution into a new 1 mL syringe.
  • Add 0.9 mL NS. Mix.
  • This results in 0.2 mg/mL.
  • Label: "Flucloxacillin SPT/IDT 0.2 mg/mL".

Skin prick test (SPT)

Reagent Concentration
Test solution 0.2 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 (20mg/ml) + 0.9 mL NS

Note: The dilution ratios are relative to the 2 mg/mL IDT starting concentration.

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