How to prepare the solution?
Thyroxin solution for skin testing can be prepared by crushing a tablet (50 mcg) and mixing with 1 mL of 0.9% phosphate-buffered saline for 2 hours.
The solution can be passed through a 0.2-micrometer-pore filter if future IV administration is indicated. This should be done by a pharmacist.
How to do the skin test?
Prick test with levothyroxine solutiion, 50 mcg/mL. If negative, do intradermal testing with 0.02 mL of the solution in concentrations of 1:100,000, 1:10,000, 1:1,000, 1:100, and 1:10.
If the tests are negative, a challenge with levothyroxine should be performed if indicated.
Drug allergy management in 5 steps (click to enlarge the image).
IMMEDIATE-TYPE HYPERSENSITIVITY REACTION TO LEVOTHYROXINE AND DESENSITIZATION - Annals of Allergy, Asthma & Immunology http://buff.ly/1BHCa1C
Levothyroxine anaphylaxis? Vocal cord dysfunction mimicking an anaphylactic drug reaction - Annals of Allergy, Asthma & Immunology http://buff.ly/1FF8r6F
Image source: Wikipedia, public domain.