Safety and reliability of challenge test for alternative drugs (tolerance test): our experience on 739 patients

BACKGROUND: Drug tolerance tests (DTTs) are commonly used to find a safe therapeutic alternative for patients with previous type B adverse drug reactions (ADRs), but few studies on safety and reliability are available. METHODS: We retrospectively studied 739 subjects with previous ADRs who underwent DTTs; 12 months after the test, use of the tested drug(s) and occurrence of ADRs were investigated in 260 of them. RESULTS: ADRs to antibiotics and nonsteroidal anti-inflammatory drugs were the main reasons for which DTTs were requested. 925 DTTs were performed in the 739 patients, with 97 ADRs. Twelve months after the test, 125/260 patients interviewed had used the tested drug(s): 118 of them experienced no ADR, 4 experienced 'true' ADRs, and 3 reported predictable/unclear reactions. CONCLUSION: Our data show that DTTs are safe and reliable at 1 year, but patients and general practitioners do not trust them. It is strongly advisable to have better information on methods, benefits, risks and reliability of DTTs.