Q:

2/11/2013
My pharmacy will be supporting our new allergy clinic in compounding/admixing skin test for drug-induced allergies. Are there any general guidelines for diluting oral drugs for this purpose? I have found some guidelines from the European Network for Drug Allergy such as dilution ranges and recommended levigating agents and dilution vehicles for hydrophobic drugs as well as the need for the purest drug form of the oral drug (parental formulations preferred) in order to eliminate/minimize excipient agents. Testing methods and preparations in studies and articles have provided information as well. Thank you as always for your feedback.

A:

Thank you for your inquiry.

There are a number of sources which offer some guidance to help one skin test to drugs. However, for the most part, these are general comments, and for information regarding skin testing to a specific drug, oftentimes the best procedure is to search the literature for previously published cases to obtain an already established protocol.

I assume the European guidelines you mentioned is the same as I have copied below in the form of an abstract (Barbaud A, et al.). The entire guidelines can be obtained as they appear in the journal “Contact Dermatitis” in the form of a PDF without charge by clicking on the link copied below. The name of the journal shouldn't mislead you since both intra and epicutaneous testing are discussed along with patch tests.

In addition, I have attached for you a document that gives guidance to pharmacists in the preparation of drugs for skin testing. It appeared in a 2006 (Volume 12) issue of EJHP Practice.

The British Society also has a PDF that is available free of charge, and that link is copied below. It appeared in Clinical and Experimental Allergy in 2008.

Finally, our own Practice Parameters speak to this issue in both the Parameter on Allergy Testing and the Parameter on Drug Allergy.

Thank you again for your inquiry and we hope this response is helpful to you.

Contact Dermatitis. 2001 Dec;45(6):321-8.
Guidelines for performing skin tests with drugs in the investigation of cutaneous adverse drug reactions.
Barbaud A, Gonçalo M, Bruynzeel D, Bircher A; European Society of Contact Dermatitis.
Source
Dermatology Department, Hopital Fournier, 54000 Nancy, France.
Abstract
Skin testing with a suspected drug has been reported to be helpful in determining the cause of cutaneous adverse drug reactions (CADR). Many isolated reports of positive drug skin tests are published, but without detailed information concerning the clinical features of the CADR and the method used in performing drug skin tests, such data are not very informative. A working party of the European Society of Contact Dermatitis (ESCD) for the study of skin testing in investigating cutaneous adverse drug reactions, has proposed the herein-reported guidelines for performing skin testing in CADR in order to standardize these procedures. In each reported case, the imputability of each drug taken at the onset of the CADR and a highly detailed description and characterization of the dermatitis need to be given. Drug skin tests are performed 6 weeks to 6 months after complete healing of the CADR. Drug patch tests are performed according to the methods used in patch testing in studying contact dermatitis. The commercialized form of the drug used by the patient is tested diluted at 30% pet. (pet.) and/or water (aq.). The pure drug is tested diluted at 10% in pet. or aq. In severe CADR, drug patch tests are performed at lower concentrations. It is also of value to test on the most affected site of the initial CADR. Drug prick tests are performed on the volar forearm skin with the commercialized form of the drug, but with sequential dilutions in cases of urticaria. Intradermal tests (IDT) are performed with sterile sequential dilutions (10-4, 10-3, 10-2, 10-1) of a pure sterile or an injectable form of the suspected drug with a small volume of 0.04 ml. Drug skin tests need to be read at 20 min and also later at D2 and D4 for patch tests, at D1 for prick tests and IDT. All these tests also need to be read at 1 week. The success of skin tests varies with the drug tested, with a high % of positive results, for example, with betalactam antibiotics, pristinamycin, carbamazepine and tetrazepam on patch testing, or with betalactam antibiotics and heparins on delayed readings of IDT. The results of drug skin tests also depend on the clinical features of the CADR. The use of appropriate control patients is necessary to avoid false-positive results.

Guidelines for performing skin tests with drugs in the investigation of cutaneous adverse drug reactions

EJHPPractice
Volume 12 • 2006/4
Pharmacy Prearation of Allergy Tests

BSACI guidelines for the management of drug allergy

Allergy diagnostic testing: an updated practice parameter (2008)

Drug allergy: an updated practice parameter (2010)

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology