A) Dilute the drug to
10,000 units/mL as shown below:
Material: Penicillin
G 600mg/vial (1,000,000u/vial)
Dilution method:
- Pen G 1 vial + 1ml water for injection = 1,000,000u/ml (Solution A)
- With 10 ml syringe with needle, dilute 0.1 ml of Solution A with 10 ml water for injection = 100,000 units/ml (Solution B)
- With 10ml syringe, dilute 1ml of Solution B with 10ml of water for injection= 10,000 units/ml
*This dilution is used for testing (prick and intradermal).
B) Prick or
percutaneous testing is done first.
Reagents
for prick and intradermal:
- Negative Control: Sodium chloride solution without preservative
- Penicillin G 10,000 U/ml (a minor determinant)
Method:
a)
A drop of the diluted drug (Penicillin G 10,000
U/ml) is placed on the ventral surface of the forearm and the skin pricked
through the drop.
b)
Prick-puncture skin testing results are read 15 minutes after application:
Results interpretation
|
|
Positive response
|
Wheal that is ≥3 mm in mean diameter than the negative control.
|
Negative response
|
No reaction at the prick site or erythema alone without a wheal.
|
c) If the prick test is negative, it is followed by the
intradermal skin test.
C) INTRADERMAL SKIN
TEST
a)
The forearm is injected 0.02 - 0.03 ml using the
same reagents intradermally.
b)
Read the results 15 to 20 minutes after application:
Results interpretation
|
|
Positive response
|
Wheal that has increased in size from the original bleb & is ≥ 3
mm in mean diameter than the negative control.
|
Negative response
|
No increase in the size of the original bleb and no wheal greater
than the control site.
|
TEST DOSE CHALLENGE WHEN SKIN TESTING IS NEGATIVE
Test dose may be given and then observe for 30 minutes,
followed by the remaining or full oral dose with monitoring for 30-60 minutes.
References:
1. Beta-lactam
antibiotic skin testing and oral challenge. From the ACAAI 2015 Drug Allergy and Anaphylaxis Committee
2. Saniel,
Mediadora C., et al. "Antibiotic Skin Testing." Workshop held on
February. Vol. 5. 1991.
3. Solley, Graham O. "Testing for drug allergy." Australian
Prescriber 17.3 (1994).
4. www.uptodate.com
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