Non-pigmenting cutaneous-mucosal fixed drug eruption due to piroxicam.

BACKGROUND: Piroxicam is a widely used anti-inflammatory drug. Most adverse reactions affect gastrointestinal system, liver and skin. Fixed drug eruption although very unusual, has also been described, but with cutaneous involvement exclusively. We present the case of a 49-year-old man who suffered three episodes of fixed drug eruption with cutaneous-mucosal involvement, even simulating an autoimmune disease, whenever he was treated with oral piroxicam. METHODS AND RESULTS: He was patch tested on normal skin with the GEIDC standard series and an NSAIDs series. He was patch tested on normal skin and on fixed eruption with piroxicam, meloxicam and tenoxicam (all of them 1 % pet). Oral challenge test was not performed due to the severity and reproducibility in previous reactions. Results showed a positive patch test to piroxicam (1 % pet) on fixed eruption, with negative results to the rest. CONCLUSIONS: Adverse drug reactions may present a wide variability of clinical symptoms. In these situations an accurate clinical history is necessary. To our knowledge this is the 1st report of non-pigmenting fixed drug eruption with cutaneous-mucosal involvement due to piroxicam. Cross-reactivity between oxicams could not be demonstrated by patch test on fixed eruption.

Non-pigmenting cutaneous-mucosal fixed drug eruption due to piroxicam

Background: Piroxicam is a widely used anti-inflammatory drug. Most adverse reactions affect gastrointestinal system, liver and skin. Fixed drug eruption although very unusual, has also been described, but with cutaneous involvement exclusively. We present the case of a 49-year-old man who suffered three episodes of fixed drug eruption with cutaneous-mucosal involvement, even simulating an autoimmune disease, whenever he was treated with oral piroxicam. Methods and results: He was patch tested on normal skin with the GEIDC standard series and an NSAIDs series. He was patch tested on normal skin and on fixed eruption with piroxicam, meloxicam and tenoxicam (all of them 1 % pet). Oral challenge test was not performed due to the severity and reproducibility in previous reactions. Results showed a positive patch test to piroxicam (1 % pet) on fixed eruption, with negative results to the rest. Conclusions: Adverse drug reactions may present a wide variability of clinical symptoms. In these situations an accurate clinical history is necessary. To our knowledge this is the 1st report of non-pigmenting fixed drug eruption with cutaneous-mucosal involvement due to piroxicam. Cross-reactivity between oxicams could not be demonstrated by patch test on fixed eruption (AU)

Introducción: El piroxicam es un fármaco antiinflamatorio ampliamente utilizado. La mayor parte de las reacciones adversas producidas por él afectan al aparato digestivo, al hígado y a la piel. La erupción fija medicamentosa, con una frecuencia de aparición muy escasa, también se ha descrito, aunque con afectación exclusivamente cutánea. Presentamos el caso de un varón de 49 años que tuvo tres episodios de erupción fija con afectación cutáneo-mucosa, simulando una enfermedad autoinmune, coincidiendo con la administración oral de piroxicam. Material y método: Se realizaron pruebas epicutáneas con la batería estándar del GEIDC y una batería de AINE sobre piel sana. Sobre la erupción fija y también sobre piel sana se aplicaron parches con piroxicam, tenoxicam y meloxicam (todos ellos al 1 per cent vaselina).No se realizó prueba de exposición oral a causa de la gravedad y reproducibilidad de las reacciones previas. Los resultados fueron positivos, de forma exclusiva, con el parche de piroxicam (1 per cent vaselina) sobre la erupción fija. Conclusiones: Las reacciones adversas medicamentosas pueden presentar una amplia variabilidad en sus manifestaciones clínicas. En estas situaciones es necesario realizar una anamnesis muy minuciosa. De acuerdo con la bibliografía existente, este es el primer caso descrito de erupción fija no pigmentaria por piroxicam con afectación cutáneo-mucosa. La reactividad cruzada entre oxicams no pudo demostrarse mediante la aplicación del patch test sobre la erupción fija (AU)

On the relationship between two models of neural entrainment.

A comparison is established between the two models of neural entrainment proposed by Nagumo and Sato (1972) and by Torras (1986). Both are formulated in terms of a transition equation whose solutions of period m correspond to the different (m:r)-entrainment patterns. The existence of a transformation relating both transition equations implies the equivalence between stable entrainment for the former model and unstable entrainment for the latter one. However, there is no counterpart for the stable entrainment arising in Torras' model.

Entrainment in pacemakers characterized by a V-shaped PRC.

The behaviour of a class of pacemakers characterized by a V-shaped PRC has been determined, for all possible frequencies and amplitudes of stimulation. The analytical study of the phase transition equation reveals that all rhythmic stimuli, but for a set of measure zero, give rise to entrainment. The ratio between firing and stimulation frequencies is a generalized Cantor function of the ratio between spontaneous and stimulation frequencies. A procedure to compute the detailed input/output pattern that underlies each entrainment ratio is given. Finally, the neurophysiological assumptions and implications of the results obtained are discussed.

Pacemaker neuron model with plastic firing rate: entrainment and learning ranges.

The model proposed puts forward a hypothesis on how some pacemaker neurons learn to fire at the frequency imposed by the stimulation. It builds on previous developments in two separate research fields: neural modelling and neuronal learning theory, providing an electrophysiological model of neuronal learning. Simulation results are shown to be in qualitative agreement with experimental data reported for Aplysia and crayfish. The analytical study of the PRC reveals that the postulated learning rule tends to favour the emergence of simple entrainment ratios. The model is worth consideration not only because of its autonomous functioning, described in this paper, but also because it constitutes a suitable building-block for a net aimed at reproducing the temporal-pattern learning phenomena shown by some neural structures.