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Protaphane

Overview

Field Detail
Drug class Intermediate-acting insulin (isophane)
Route SC
Stock vial 100 units/mL (10 mL vial)
Reconstituted conc. N/A (Ready to use; resuspend before use)
Diluent 19 mL N/S 0.9% for SPT dilution
Storage Refrigerated (2–8 °C); Do not freeze; In-use vials may be kept at room temp for up to 28 days

Note

Insulin units (U) are used instead of mg/mL for concentration reporting. Resuspend the vial by gently rolling between the palms before use — do not shake vigorously.

Preparation

Before you start

Check the expiry date and vial integrity before opening. Label every syringe immediately after drawing up — never leave unlabelled syringes on the tray. Resuspend the insulin by gently rolling the vial between your palms until the suspension is uniformly cloudy.

Equipment needed

  • 1 × Protaphane 100 U/mL (10 mL vial)
  • Normal saline (NS) 0.9% — for IDT dilutions
  • 1 mL syringes × 3 (for test doses/dilutions)
  • 25 G needles

Step 1 — Prepare the SPT solution (100 U/mL — neat)

  1. Gently resuspend the vial by rolling between palms.
  2. Draw up 0.5–1 mL of the stock (100 U/mL) into a 1 mL syringe.
  3. Label: "Protaphane SPT 100 U/mL".

Step 2 — Prepare IDT dilutions

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

  1. IDT 5 U/mL (1:20):
    • Draw 0.1 mL of stock (100 U/mL) into a 1 mL syringe. Add 1.9 mL NS. Mix. (This is 5 U/mL — 1:20).
    • Label: "Protaphane IDT 5 U/mL".

Skin prick test (SPT)

Reagent Concentration
Test solution Neat (100 U/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 1:20 5 U/mL 0.1 mL stock (100 U/mL) + 1.9 mL NS

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