Cristina Silva

A flow microcalorimetric study of the inhibition of acetylcholinesterase by catecholamine derivatives

Abstract A flow microcalorimetric method has been applied to the determination of acetylcholinesterase activities in crude tissue homogenates. This simple and sensitive method, which measures the heat generated by a reaction, is also suitable for the study of the inhibition of the enzyme by specific compounds. In the present work this method was used to determine the effect of catecholamines and their derivatives on the acetylcholinesterase activity. The results indicate that epinephrine, norepinephrine and dopamine, in concentrations up to 2.5 mM, do not inhibit acetylcholinesterase, whereas metanephrine (0.8 mM), normetanephrine (0.8 mM), 3-methoxydopamine (0.6 mM) and l -dopa (0.7 mM) decrease the enzyme activity by 37, 75, 50 and 20%, respectively. The apparent inhibition rate constants determined for these compounds are 0.09, 0.34, 0.18 and 0.19 mM−1 min−1. A comparison of the chemical structure and inhibitory potency of the catecholamine derivatives suggests that a 3-methoxy group is responsible for the inhibition of the enzyme and that a α-carboxyl group also reduces the acetylcholinesterase activity. The comparative assays for the determination of acetylcholinesterase activities, using a flow microcalorimeter and a pH-meter, indicate that flow microcalorimetry is a useful method for enzyme kinetic studies because it has a high sensitivity and can be applied whenever heat exchange is involved in an enzymatic reaction.

Online drug databases: a new method to assess and compare inclusion of clinically relevant information

Background Evidence-Based Practice requires health care decisions to be based on the best available evidence. The model “Information Mastery” proposes that clinicians should use sources of information that have previously evaluated relevance and validity, provided at the point of care. Drug databases (DB) allow easy and fast access to information and have the benefit of more frequent content updates. Relevant information, in the context of drug therapy, is that which supports safe and effective use of medicines. Accordingly, the European Guideline on the Summary of Product Characteristics (EG-SmPC) was used as a standard to evaluate the inclusion of relevant information contents in DB. Objective To develop and test a method to evaluate relevancy of DB contents, by assessing the inclusion of information items deemed relevant for effective and safe drug use. Method Hierarchical organisation and selection of the principles defined in the EGSmPC; definition of criteria to assess inclusion of selected information items; creation of a categorisation and quantification system that allows score calculation; calculation of relative differences (RD) of scores for comparison with an “ideal” database, defined as the one that achieves the best quantification possible for each of the information items; pilot test on a sample of 9 drug databases, using 10 drugs frequently associated in literature with morbidity-mortality and also being widely consumed in Portugal. Main outcome measure Calculate individual and global scores for clinically relevant information items of drug monographs in databases, using the categorisation and quantification system created. Results A—Method development: selection of sections, subsections, relevant information items and corresponding requisites; system to categorise and quantify their inclusion; score and RD calculation procedure. B—Pilot test: calculated scores for the 9 databases; globally, all databases evaluated significantly differed from the “ideal” database; some DB performed better but performance was inconsistent at subsections level, within the same DB. Conclusion The method developed allows quantification of the inclusion of relevant information items in DB and comparison with an “ideal database”. It is necessary to consult diverse DB in order to find all the relevant information needed to support clinical drug use.