Morphine¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | Opioid analgesic |
| Stock vial | 10 mg/mL |
| Reconstituted conc. | N/A (Ready to use) |
| Storage | Room temp; Protect from light |
Preparation¶
Before you start
Ensure the vial contains 10 mg/mL. Check expiry and integrity. Note that Morphine is a Schedule 8 (S8) medication and requires appropriate handling and witnessing. SPT is NOT performed neat for Morphine as it is a potent histamine-releaser.
Equipment needed¶
- 1 × Morphine 10 mg/mL vial
- Normal saline (NS) — for dilutions
- 1 mL syringes × 5 (for test doses/dilutions)
- 25 G needles
Step 1 — Prepare the SPT solution (1 mg/mL — 1:10)¶
- Draw up 0.1 mL of the stock (10 mg/mL) into a 1 mL syringe.
- Add 0.9 mL NS. Mix. (This is 1 mg/mL — 1:10).
- Label: "Morphine SPT 1 mg/mL (1:10)".
Step 2 — Prepare IDT dilutions¶
Prepare in this order, using a fresh syringe for each step.
- IDT 0.0001 mg/mL (1:100,000):
- 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).
- D: Draw 0.1 mL of C (0.01 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.001 mg/mL — 1:10,000).
- E: Draw 0.1 mL of D (0.001 mg/mL) into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.0001 mg/mL — 1:100,000).
- Label: "Morphine IDT 0.0001 mg/mL".
Skin prick test (SPT)¶
| Reagent | Concentration |
|---|---|
| Test solution | 1:10 (1 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 | 1:100,000 | 0.0001 mg/mL | 0.1 mL of 0.001 mg/mL + 0.9 mL NS |
Potent Histamine Releaser
Morphine is a potent direct histamine releaser. Results must be interpreted with caution. IDT should be performed at very high dilutions (1:100,000) as per the institutional protocol.
Inject: 0.05 mL intradermal. Read at 15–20 minutes.