[Oral exposure testing in non-aspirin-induced analgesic intolerance]

Although intolerance reaction to analgesics are not uncommon, there is still a lack of standardized procedures to diagnose the problem. We retrospectively analyzed results of scratch tests as well as oral challenges with analgesics in order to evaluate risk and diagnostic relevance of these procedures. In 1987-1992 a total of 650 patients with supposed intolerance to drugs were tested by oral challenge. Among them were 98 patients with a positive history of intolerance to non-aspirin analgesics. In 56 patients the intolerance could be verified by oral challenge. In order of decreasing frequency, the most likely agents were propyphenazone, diclofenac, metamizole, ibuprofen, carbamazepine, indomethacin, phenazone (antipyrine), and paracetamol (acteaminophen). Oral provocation showed clear dose-response relationships. For propyphenazone, the half-effective provocation dose was the same for all symptoms (cutaneous, nasal, bronchial, anaphylactoid). Scratch testing was not of diagnostic significance. Standardized test protocols starting with low dose oral challenges are suitable and helpful in minimizing the risk of severe side effects.