Place of Drug Skin Tests in Investigating Systemic Cutaneous Drug Reactions

Abstract

Skin tests with drugs can be helpful in determining the cause of cutaneous adverse drug reactions (CADR). Patch tests and prick tests can be done with any commercialized form of a drug, intradermal tests (IDT) normally rely on the availability of a sterile solution used for parental applications. There has been some experience with different concentrations and techniques, but a complete standardization has not been done with these tests. Prick tests and IDT are used to investigate immediate hypersensitivity, patch tests and IDT with delayed readings are helpful for symptoms appearing delayed. They can be positive in different skin symptoms, with or without involvement of internal organs (e.g. hepatitis). A great variety of drugs can be tested, including antibiotics, antiepileptics, drugs used in oncology, drugs used for diagnosis etc. Except for IDT, skin tests with drugs rarely induce adverse reactions. False positive results can occur and should be considered, if a product for skin tests is evaluated for the first time. The negative predictive value of skin tests with drugs is a crucial point that will have to be studied in detail in the near future.

Lichenoid drug eruption induced by misoprostol

“…We found a weak positive reaction to the first (probably due to the very low concentration) but a stronger reaction to the pure substance. Such low concentrations are recommended when testing misoprostol because, according to Barbaud et al (8, 9), the commercial form of the drug (Cytotec) diluted at 30% in petrolatum frequently gave positive reactions when tested in control subjects (false positive results), whereas they were negative when diluted at 1% in petrolatum.…”

Eosinophilic drug reactions detected by a prospective pharmacovigilance programme in a tertiary hospital

“…In DRESS cases, the exanthema index day was the day in which the exanthema appeared, and the prodromal index day was the day in which the first symptom or sign occurred. Drug causality for DRESS syndrome patients was additionally established by allergological study, including a lymphocyte transformation test (LTT), and epicutaneous, prick, and intradermal (ID) tests .…”

Stamping a case of cutaneous adverse drug reaction: Proving beyond causality assessment

“… In general, it is advised to perform the tests 6 weeks to 6 months after the hypersensitivity reaction because it is not known whether or not positive results will persist and whether or not some drug reactivities will last longer. [ 11 14 15 ] Ideally, immediate skin testing should be performed after an interval that allows resolution of clinical symptoms and clearance of a suspected drug. It is important to avoid antihistamines (up to 7 days) before testing.…”

“…In general, it is advised to perform the tests 6 weeks to 6 months after the hypersensitivity reaction because it is not known whether or not positive results will persist and whether or not some drug reactivities will last longer. [ 11 14 15 ]…”