Estudo da estabilidade térmica de suspensöes orais de cefalexina / Study of thermal stability of oral suspensions of cephalexin

A cefalexina é um antibiótico cefalosporânico de primeira geração sintetizado no final da década de setenta e utilizado principalmente no tratamento de infecções do sistema respiratório, causadas por microrganismos Gram positivos. Devido a sua estabilidade em meio ácido, as preparações farmacêuticas contendo cefalexina apresentam excelente absorção por via oral, sendo disponibilizadas no comércio na forma de comprimidos, cápsulas e suspensões orais. Apesar do amplo emprego deste antibiótico existem poucos dados na literatura a respeito da estabilidade da cefalexina em preparações farmacêuticas. Particularmente, em relação às suspensões orais, o estudo de estabilidade torna-se mais difícil devido à complexidade da formulação e às inúmeras interções que podem ocorrer entre o fármaco e os excipientes utilizados...

Cross-reactivity of T cell lines and clones to beta-lactam antibiotics.

To clarify on a molecular level the specific T cell response to haptens like penicillin G, we generated T cell lines and clones from penicillin-allergic patients. Two types of beta-lactam reactivity of T cells could be delineated: one group of patients showed a rather restricted specificity, as the penicillin-elicited T cell lines generated from such donors proliferated only to the stimulating penicillin, but not to other beta-lactam antibiotics nor to cephalosporines, even if the side chain was identical. This indicates that the penicilloyl structure together with the side chain was recognized by these T cells. The second group comprised patients with more broadly reactive T cells, as they were restimulated by penicillin G as well as by related penicillins like amoxicillin or ampicillin, but not cephalosporines. This indicates that the penicilloyl structure, a common motif of penicillins, was important for T cell recognition. Clones generated from a broadly reactive patient confirmed this heterogeneity, as either monospecific or broadly specific T cell clones could be identified. This broad or very restricted pattern of T cell reactivity was reflected in the use of TCR Vbeta-chains: while the broadly reactive T cell lines showed a heterogenous TCR usage, the highly restricted T cell lines showed an up-regulation of one TCR Vbeta-chain. Thus, our data suggest that the outgrowth of T cells bearing a certain TCR Vbeta may be a sign of a limited cross-reactivity.