An experimental and theoretical approach on oxidative metabolism of paracetamol was applied for the pharmaceutical chemistry learning. Classical reactions, functional group identification, structural parameter, and chemical reactivity using frontier orbitals and Fukui index were used explaining the main products between N-acetyl-p-benzosemiquinone (NAPQI) and thiolic compounds. The chemoprotection mechanisms by N-acetyl-cysteine on high dosage of paracetamol are consistent with theoretical and experimental results. The methods also described the relationship between the chemical reactivity of quinone-imine system and the induced-toxicity of paracetamol by Michael reaction. These results can be applied in experimental pharmaceutical chemistry teaching.

Objetivos: Avaliar a validade concorrente do desempenho no teste de degrau de seis minutos (TD6) em analisar a capacidade física da DPOC, relacionando-o com o teste de caminhada de seis minutos (TC6), bem como verificar a presença de validade de critério preditiva do TD6, determinando um valor de corte para identificar baixa capacidade física. Método: Trinta e dois pacientes com DPOC estágios leve-muito grave, de ambos os sexos, entre 50-87 anos, realizaram dois TD6 e dois TC6. Resultados: Validade concorrente: observou-se correlação forte positiva (Pearson) entre o número de subidas do primeiro (T1), segundo (T2) e do melhor dos dois (T1 ou T2) TD6 com a distância percorrida no TC6. Embora constatamos correlações negativas entre os desempenhos no TD6 com o índice BODE e VEF1, essas não foram suficientes para caracterizar validade, não sendo traçadas as curvas ROC. A validade preditiva (curvas ROC) do TD6 para identificar baixa capacidade física (comparação com o TC6), utilizando o desempenho do T1 ou T2 ou somente do T1, foi considerada acurada para alguns propósitos, sendo a área abaixo da curva de 0,8 (IC95% 0,62-0,98) e 0,85 (IC95% 0,70-0,99), respectivamente. Para classificar os pacientes, escolhemos o ponto de corte de 86 e 78 degraus, apresentando sensibilidade de 90% e 90% e especificidade de 64% e 68%, para T1 ou T2 e somente T1, respectivamente. Conclusão: O desempenho no TD6 apresentou-se válido para verificar capacidade física na DPOC e identificou pacientes com baixa capacidade física, utilizando como ponto de corte 78 degraus, em que valores abaixo disso representaram pior prognóstico.

Objectives: to evaluate the concurrent validity of the six-minute step test (6MST) in assessing exercise capacity of COPD patients using the six-minute walk test (6MWT) as a gold-standard. The predictive validity of the 6MST was assessed to determine a cut-off point for identification of low exercise capacity. Method: thirty-two COPD patients (50-87 years old) with mild to very severe obstruction performed the 6MST and 6MWT twice. Results: Concurrent validity: a strong positive correlation (Pearson) between the number of ascents on the first (T1), second (T2) and the best of both (T1 or T2) tests during the 6MWT was observed. Although a moderate negative correlation with BODE index and FEV1 was found, it was considered insufficient to test the validity, therefore ROC curves were not applied. The predictive validity (ROC) of the 6MST to identify low physical capacity (compared with the 6MWT) using the performance of T1 or T2, or solely T1 was considered accurate, and the area under the curve was 0.8 (IC95% 0.62-0.98) and 0.85 (IC95% 0.70-0.99), respectively. To classify patients, the cut-off points of 86 and 78 steps were chosen, with both values showing 90% of sensitivity and specificity of 64% and 68% for T1 or T2, or solely T1, respectively. Conclusion: The number of steps on the 6MST was valid to verify exercise capacity in COPD patients and the cut-off point of 78 steps was able to identify patients with poor exercise tolerance. Values under this cut-off point are considered to identify patients with a poorer prognosis.