Effect of Chitosan Addition in Whey-based Biodegradable Films

Abstract Whey, a by-product of dairy industry, is a feedstock widely employed in the production of biodegradable films. However, these films present some limitations when considering the performance of synthetic polymers, especially biological transformation by decomposition. This work aimed to evaluate the effects of chitosan addition to whey-based films to improve films physical-chemical properties and resistance to microbial degradation. The results showed that there was an interaction effect between the chitosan concentration and the storage time for the physical-chemical properties of elongation at break and opacity. There was statistical difference among the formulations; however, for the moisture content and film thickness, there was no interaction effect between the formulation and the storage time. The films with 1.5 and 3.0 wt.% chitosan presented a yellowish hue, characteristic of the polysaccharide; this could also be detected by SEM analysis. The films presented an excellent biodegradability, being decomposed in about 8 days. Considering all chitosan contents tested had similar performances, the chitosan content of 0.15 wt.% was the one with the better cost-benefit relation.

Warfarin: pharmacological profile and drug interactions with antidepressants / Varfarina: perfil farmacológico e interações medicamentosas com antidepressivos

Oral anticoagulants are among the drugs with the greatest number of drug interactions. The concomitant use of several medications is a common practice in patients with cardiovascular problems, who often also present with depression; therefore, the probability of an interaction occurring between warfarin and the antidepressants is high, and may result in increased or decreased anticoagulant activity. Since the possible interactions between these two classes of drugs have been poorly explored in literature, with a risk to the patients who use them, we reviewed the pharmacology of warfarin and its possible interactions with antidepressants. Of the antidepressants analyzed, those that showed relevant effects on the interaction with warfarin were, in decreasing order: paroxetine, venlafaxine, fluoxetine, and duloxetine.

Os anticoagulantes orais estão entre as drogas com maior número de interações medicamentosas. O uso concomitante de vários medicamentos é uma prática comum em pacientes com problemas cardiovasculares, os quais frequentemente também apresentam depressão; assim, a probabilidade de ocorrer alguma interação entre a varfarina e os antidepressivos é bem expressiva, podendo resultar em um aumento ou uma diminuição da atividade anticoagulante. Como as possíveis interações entre essas duas classes de medicamentos se mostraram pouco exploradas na literatura, com risco aos pacientes que fazem uso delas, revisamos a farmacologia da varfarina e suas possíveis interações com antidepressivos. Dos antidepressivos analisados, os que apresentaram efeitos relevantes na interação com a varfarina foram, em ordem decrescente: paroxetina, venlafaxina, fluoxetina e duloxetina.

Modulation of thymidine kinase activity: a biochemical strategy to enhance the activation of antineoplastic drugs

Thymidine kinase is a key enzyme responsible for the activation of several anticancer and antiviral drugs. As the first enzyme in the salvage pathway of thymidine, it is regulated by the feedback inhibition exerted by the end-product of the pathway, namely thymidine 5'-triphosphate. 5'-Aminothymidine is a non-toxic analogue of thymidine capable of interfering with this regulatory mechanism. In fact, it has been shown that 5'-aminothymidine increases the cytotoxicity and metabolism of various thymidine analogues currently in use of the clinic as antineoplastic agents. This mini-review article focuses in the evidence supporting the role of 5'-aminothymidine as a potential prototype drug for a new class of anticancer agents: drugs which affect the regulation of key metabolic pathways that determine the efficacy of agents with cytotoxic activity. The mechanism of action, antineoplastic activities and basis for selectivity in tissue culture models are also described