Surface degradation of composite resins by acidic medicines and ph-cycling

This study evaluated the effects of acidic medicines (Dimetapp® and Claritin®), under pH-cycling conditions, on the surface degradation of four composite resins (microhybrid: TPH, Concept, Opallis and Nanofilled: Supreme). Thirty disc-shaped specimens (Ø = 5.0 mm / thickness = 2.0 mm) of each composite were randomly assigned to 3 groups (n = 10): a control and two experimental groups, according to the acidic medicines evaluated. The specimens were finished and polished with aluminum oxide discs, and the surface roughness was measured by using a profilometer. After the specimens were submitted to a pH-cycling regimen and immersion in acidic medicines for 12 days, the surface roughness was measured again. Two specimens for each material and group were analyzed by scanning electron microscopy (SEM) before and after pH-cycling. Data were analyzed by the Student's-t test, ANOVA, Duncan's multiple range test and paired t-test (α=0.05). Significant increase in roughness was found only for TPH in the control group and TPH and Supreme immersed in Claritin® (p<0.05). SEM analyses showed that the 4 composite resins underwent erosion and surface degradation after being subjected to the experimental conditions. In conclusion, although the roughness was slightly affected, the pH-cycling and acidic medicines caused surface degradation of the composite resins evaluated. Titratable acidity seemed to play a more crucial role on surface degradation of composite resins than pH.

Efeitos cardiovasculares e midriáticos da fenilefrina tópica a 2,5 e a 10,0 por cento em voluntários sadios / Cardiovascular and pupillary effects of topical ophthalmic 2.5 and 10.0 percent phenylephrine in healthy volunteers

OBJETIVO: Comparar os efeitos cardiovasculares e midriáticos da fenilefrina tópica nas concentrações de 2,5 e 10,0 por cento. MÉTODOS: Ensaio clínico do tipo caso controle, randomizado, com auto-emparelhamento. Foram monitoradas a freqüência cardíaca (FC), a pressão arterial (PA) e a midríase em voluntários sadios, com idade entre 18 e 45 anos, após a instilação da fenilefrina a 2,5 e a 10,0 por cento em duas ocasiões diferentes. RESULTADOS: A amostra foi constituída de 28 voluntários, sendo 17 do sexo masculino e 11 do sexo feminino, com a idade média de 26,5 anos. Não foi verificado nenhum padrão de mudanças com relação à freqüência cardíaca e à pressão arterial sistólica. Com relação à pressão arterial diastólica média dos indivíduos, não foi encontrada variação significativa após a instilação da fenilefrina a 2,5 por cento nos tempos de um, cinco, dez e 30 minutos, o que se revelou bem diferente quando do uso da fenilefrina a 10,0 por cento, com a qual houve aumento da pressão arterial diastólica média após cinco e dez minutos, e subseqüente queda após 30 minutos, porém sem significância estatística. A midríase foi maior com a fenilefrina a 10,0 por cento nos dois olhos, sendo a diferença estatisticamente significativa. CONCLUSÕES: Observou-se maior efeito midriático da fenilefrina a 10,0 por cento, quando comparada a 2,5 por cento, com significância estatística. Já com relação aos efeitos cardiovasculares não houve diferença estatística entre as duas concentrações.

PURPOSE: To compare the cardiovascular and mydriatic effects of 2.5 percent and 10.0 percent phenylephrine. METHODS: A case-control, randomized, crossover clinical trial study. We monitored heart rate (HR), blood pressure (BP) and mydriasis in healthy volunteers aged 18-45 years after the instillation of 2.5 percent and 10.0 percent phenylephrine in two different occasions. RESULTS: The sample comprised 28 healthy volunteers, 17 male and 11 female, with a mean age of 26.5 years. No changes in heart rate and systolic blood pressure were observed. No significant variation of the mean diastolic blood pressure was found after 1, 5, 10 and 30- minute instillation of 2.5 percent phenylephrine. However, with 10.0 percent phenylephrine, there was an increase in mean diastolic blood pressure after five and ten minutes, followed by a drop after 30 minutes, which was not statistically significant. Mydriasis was more marked in both eyes with a statistically significant difference after instillation of 10.0 percent phenylephrine. CONCLUSIONS: The mydriatic effect was greater with 10.0 percent phenylephrine than with 2.5 percent phenylephrine and the difference was statistically significant. No statistically significant difference was found in relation to cardiovascular effects in both phenylephrine concentrations.

Chronic Hypoxia Alters Vasoconstrictive Responses of Femoral Artery in the Fetal Sheep

The purpose of this study was to determine if mild hypoxia alters the responsiveness to vasoactive agents in the renal and the femoral arteries in the fetal sheep. Ten pregnant sheep were operated under halothane anesthesia at 116 to 124 days' gestation. A maternal tracheal catheter was placed for infusing compressed air (control group, n=5) or nitrogen (hypoxia group, n=5) starting on post operative day 6 and maintained for 5 days. Femoral and renal arteries were harvested from the fetus to study the constriction response to phenylephrine (PE 10(-9) to 10(-5) mol/L). To determine the involvement of nitric oxide as a modulator of vessel constriction, N-nitro-Larginine methyl ester (L-NAME) was used at a concentration of 10(-4) mol/L in parallel chambers. In the hypoxia group, maternal Pao2 significantly decreased from a base-line of 110.4 +/-1.4 to 80.5 +/-1.6 (mmHg, p <0.01), fetal Pao2 significantly decreased from a baseline of 20.9 +/-0.3 to 15.5 +/-0.1 (mmHg, p <0.01). Hypoxia was associated with a significant increase in PE maximal response in the absence (184.5 +/-6.6 vs. 146.2 +/-4.3) and presence (166.9 +/-6.3 vs. 145.0 +/-4.5) of L-NAME, and a decrease in EC50 in the absence (6.0 +/-1.1 vs. 27.0 +/-4.1) of L-NAME of femoral arteries. However, there were no significant differences in PE maximal response and EC50 in the absence and presence of L-NAME of renal arteries. We concluded that mild chronic hypoxia seems to increase the fetal femoral artery response to PE, but not in the fetal renal artery. This observation is consistent with a redistribution of cardiac output away from the carcass.

Spectrophotometric determination of phenylephrine using P-aminophenol and potassium periodate

A fast and sensitive method has been developed for the determination of Phenylephrine hydrochloride [PE] in pharmaceutical preparations. The method is based on the reaction between PE and p-aminophenol [PAP] in presence of KIO[4] at pH 10. The absorbance of solution is measured at [lambda [max]] 640 nm. Beer's law is obeyed over the concentration range from 15 to 100 micro g ml[-1], and the extinction coefficient was calculated to be 1.01 x 10[3] 1 mol[-1] cm[-1]. The different analytical parameters have been investigated. The method has been successfully applied to determine PE in some pharmaceutical preparations