Penicillin Minor Determinant (MD)¶
Overview¶
| Field | Detail |
|---|---|
| Drug class | Penicillin minor determinant |
| Stock | Pre-filled vial (Sodium Benzylpenilloate) |
| Reconstituted conc. | 0.50 mg/20.00 mg per mL |
| Diluent | 1 mL Saline in phosphate buffer |
| Storage | 2–8°C |
Preparation¶
Before you start
MD is often supplied as a ready-to-use or minimally reconstituted kit. Check expiry and integrity.
Step 1 — Preparation¶
- Follow manufacturer instructions to reconstitute if necessary with the provided diluent.
- The standard RPAH testing concentration is 0.50 mg/20.00 mg per mL (Neat).
Step 2 — Prepare the SPT solution (Neat)¶
- Draw up 0.1–0.2 mL of the neat solution.
- Label: "MD SPT (Neat)".
Step 3 — Prepare IDT dilutions¶
- IDT 1:10 (0.05 mg/2.00 mg per mL): Draw 0.1 mL of neat MD into a 1 mL syringe. Add 0.9 mL of normal saline. Mix. Label: "MD IDT 1:10".
Skin prick test (SPT)¶
| Reagent | Concentration |
|---|---|
| Test solution | Neat (0.50/20.00 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 | 1:10 | 0.05/2.00 mg per mL | 0.1 mL neat + 0.9 mL normal saline |
| 2 | Neat | 0.50/20.00 mg per mL | Used for SPT and IDT final step |
Inject: 0.05 mL intradermal. Read at 15–20 minutes.
Notes¶
- MD is critical for identifying patients with penicillin allergy who may be missed by PPL and Benzylpenicillin alone.
- Often tested in conjunction with PPL and Benzylpenicillin.