Lymphocyte-stimulation tests and patch tests to carbamazepine hypersensitivity

Seven cases of severe hypersensitivity to carbamazepine (Tegretol) were described in patients with epilepsy or trigeminal neuralgia. Clinical manifestations consisted of fever, rash, facial oedema, lymphadenopathy, impaired liver function, eosinophilia and atypical lymphocytes in the peripheral blood. Lymphocyte-stimulation tests with carbamazepine in vitro showed positive results in all cases; patch tests with carbamazepine were positive in six cases. In two cases the lymphocyte-stimulation tests with carbamazepine were found to be negative during, and shortly after, the illness. However, when the tests were repeated several months later, they turned out to be positive. Lymphocyte reactivity to PPD and PHA in vitro was also impaired during the acute phase of the disease. Thus false-negative lymphocyte-stimulation tests may be found in the first months following such a hypersensitivity reaction, probably due to impaired lymphocyte reactivity. As carbamazepine is a potent drug and is often prescribed for long periods together with other anticonvulsants, it seems important to prove that the allergic reaction is caused by carbamazepine. If the lymphocyte-stimulation test in vitro or the patch test with carbamazepine is found to be negative during or shortly after the illness, they should be repeated several months later.