RESUMO:A metformina, medicamento comercializado por diversas marcas e também na forma de genérico, é um antidiabético oral pertencente à classe das biguanidas. Devido ao seu perfil de toxicidade e à sua eficácia clínica é a principal escolha no tratamento do diabetes mellitus tipo dois (DM2). Pelo seu grande uso é necessária uma discussão constante a respeito de suas características e aplicações. Objetivou-se realizar uma revisão bibliográfica, na qual serão abordadas a aplicação da metformina no tratamento de DM2 bem como suas propriedades químicas, físico-químicas, farmacocinéticas, farmacodinâmicas, seus usos clínicos, contraindicações e efeitos adversos. Revisão da literatura realizada nos bancos de dados Pubmed, Bireme, Lilacs e Scielo, bem como pesquisa nos periódicos do Portal Brasileiro da Informação Científica e livros sobre o assunto. Pelo exposto percebe-se que a metformina para pacientes diabéticos é considerada um fármaco ideal tendo ainda aplicações na terapêutica adjuvante de outros distúrbios fisiológicos. PALAVRAS-CHAVE:Biguanidas; Diabetes mellitus tipo 2; Metformina. METFORMIN: A REVIEW OF THE LITERATUREABSTRACT: Metformin, commercialized under several trademarks and also as a generic medicine, is an oral anti-diabetic drug, belonging to the biguanide class. It is actually the first choice in the treatment of Type 2 diabetes mellitus (DM2) due to its toxicity and clinical efficaciousness. It extensive use requires a constant discussion on its characteristics and applications. Current paper is a bibliographical review comprising the application of metformin in DM2 treatment as its chemical, physical-chemical, pharmacokinetic, pharmacodynamics properties, its clinical usages, contraindications and side effects. Review occurred in Pubmed, Bireme, Lilacs and SciELO data banks and in research in journals published on the Brazilian Platform in Scientific Information and in books on the subject. Results show that metformin is the best medicine for diabetic patients, with auxiliary therapy for other physiological disorders.KEY WORDS: Biguanides; Diabetes Mellitus type 2; Metformin. INTRODUÇÃOO diabetes é uma síndrome que pode ser definida como uma condição de distúrbios metabólicos heterogêneos caracterizados por hiperglicemia resultante de defeitos na secreção e ação da insulina, ou ambos (ASSOCIAÇÃO AMERICANA DE DIABETES, 2014).

Este estudo avalia a incidência de formas polimórficas do mebendazol (MBZ) em comprimidos do mercado brasileiro por testes de dissolução. O meio de dissolução indicado pela USP 30 (United States Pharmacopeia) e um meio modificado proposto foram devidamente comparados a fim de verificar se eles são capazes de diferenciar o polimorfo A do polimorfo C em comprimidos comerciais. Ensaios de testes de dissolução de misturas físicas em matérias-primas do polimorfo A e C, assim como de nove comprimidos de MBZ (disponíveis no mercado brasileiro), foram devidamente executados. Para os testes de dissolução, o meio da USP 30 (I) e um meio modificado (II) foram utilizados. O meio modificado permitiu uma reprodutibilidade e controle da qualidade confiável do polimorfismo do MBZ em comprimidos comerciais.This study evaluates the incidence of the polymorphic forms of mebendazole (MBZ) in tablets within the Brazilian market by dissolution tests. The indicated dissolution medium by the USP 30 (United States Pharmacopoeia) and a proposed modified medium were duly compared in order to verify whether they are able to discriminate the polymorph A from polymorph C in commercial tablets. Dissolution assay tests of physical mixtures in raw materials of polymorph A and polymorph C, as well as of nine tablets of MBZ (available in the Brazilian market), were properly performed. For the dissolution tests, the USP 30 medium (I) and a modified medium (II) were used. The modified medium allowed a reproducible and reliable quality control of MBZ polymorphism in commercial tablets.

A new metalloendopeptidase was purified to apparent homogeneity from a homogenate of normal human brain using successive steps of chromatography on DEAE-Trisacryl, hydroxylapatite and Sephacryl S-200. The purified enzyme cleaved the Gly 33 -Leu 34 bond of the 25-35 neurotoxic sequence of the Alzheimer ß-amyloid 1-40 peptide producing soluble fragments without neurotoxic effects. This enzyme activity was only inhibited by divalent cation chelators such as EDTA, EGTA and o-phenanthroline (1 mM) and was insensitive to phosphoramidon and captopril (1 µM concentration), specific inhibitors of neutral endopeptidase (EC 3.4.24.11) and angiotensin-converting enzyme (EC 3.4.15.1), respectively. The high affinity of this human brain endopeptidase for ß-amyloid 1-40 peptide (Km = 5 µM) suggests that it may play a physiological role in the degradation of this substance produced by normal cellular metabolism. It may also be hypothesized that the abnormal accumulation of the amyloid ß-protein in Alzheimer's disease may be initiated by a defect or an inactivation of this enzyme.

Peptide hormone inactivating endopeptidase (PHIE) is a metalloendopeptidase which was isolated from the skin granular gland secretions of Xenopus laevis [Carvalho, K. M., Joudiou, C., Boussetta, H., Leseney, A. M., & Cohen, P. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 84-88]. This peptidase exhibits a thermolysin-like character and hydrolyzes bonds on the amino terminus of hydrophobic amino acids, performing cleavage of Xaa-Phe, Xaa-Leu, Xaa-Ile, Xaa-Tyr, and Xaa-Trp doublets. When the enzyme recognized a doublet of hydrophobic amino acids such as Phe6-Phe7 of somatostatin-14, Phe7-Phe8 of substance P, Phe4-Leu5 of [Leu5,Arg6]enkephalin, and Tyr4-Ile5 of angiotensin II, cleavage occurred preferentially between these residues. The use of selectively modified carboxy-terminal octapeptide fragments of atrial natriuretic factor (ANF) indicated that the enzyme tolerates as substrates only peptides bearing a P'1 bulky hydrophobic amino acid residue. Although a P'1 hydrophobic residue was a necessary condition, it was found in a number of peptides that all potential cleavage sites were not recognized by the enzyme. These data suggested that this metalloendoprotease requires for its thermolysin-like activity a preferred conformation of the peptide chain. Kinetic results obtained using a series of related substrates derived from biologically active peptides of the atrial natriuretic factor, tachykinin, and enkephalin families indicated the presence of an extended binding site accommodating at least six amino acid residues, in contrast to thermolysin (EC 3.4.24.4) and neutral endopeptidase (NEP; EC 3.4.24.11), which hydrolyze shorter homologous peptides.(ABSTRACT TRUNCATED AT 250 WORDS)

A new metalloendopeptidase was purified to apparent homogeneity from a homogenate of normal human liver using successive steps of chromatography on DEAE-cellulose, hydroxyapatite and Sephacryl S-200. The purified enzyme hydrolyzed the Pro 7 -Phe 8 bond of bradykinin and the Ser 25 -Tyr 26 bond of atrial natriuretic peptide. No cleavage was produced in other peptide hormones such as vasopressin, oxytocin or Met-and Leu-enkephalin. This enzyme activity was inhibited by 1 mM divalent cation chelators such as EDTA, EGTA and o-phenanthroline and was insensitive to 1 µM phosphoramidon and captopril, specific inhibitors of neutral endopeptidase (EC 3.4.24.11) and angiotensin-converting enzyme (EC 3.4.15.1), respectively. With M r 85 kDa, the enzyme exhibits optimal activity at pH 7.5. The high affinity of this endopeptidase for bradykinin (Km = 10 µM) and for atrial natriuretic peptide (Km = 5 µM) suggests that it may play a physiological role in the inactivation of these circulating hypotensive peptide hormones.