RESUMO
Recently, a family tree with a predisposition for the gene of multiple endocrine neoplasia Type 1 has been identified in Tasmania. As the surgical identification and localisation of parathyroid adenomas is facilitated by the administration of methylene blue, an opportunity has presented to measure the plasma concentration of methylene blue and methaemoglobin production. The study was undertaken to establish whether significant methaemoglobin concentrations were generated during the infusion and whether these concentrations could be related to the corresponding methylene blue concentrations. Mean peak methylene blue concentrations of 3.72 micrograms l-1, mean percentage methaemoglobin of 10.0 and a PaO2 within acceptable clinical ranges were found. No apparent relationship between methylene blue concentration and methaemoglobin production was found.
Assuntos
Adenoma/sangue , Anestesia Geral , Metemoglobina/biossíntese , Azul de Metileno/sangue , Neoplasias das Paratireoides/sangue , Adenoma/diagnóstico , Adenoma/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Cinética , Masculino , Azul de Metileno/farmacologia , Pessoa de Meia-Idade , Neoplasias das Paratireoides/diagnóstico , Neoplasias das Paratireoides/cirurgiaRESUMO
Methylene blue oxidizes uric acid to allantoin in vitro, analogous to the reaction between uric acid and phosphotungstate, although the rate is considerably slower. The reaction requires oxygen and produces hydrogen peroxide. As little as 10 micromol of methylene blue per liter in a serum sample will produce a measurable difference in the apparent uric acid concentration within 4 h at room temperature. Methylene blue may be administered for various medical reasons. If uric acid is to be measured in such sera, the procedure should be performed within 30 min, whatever method of analysis is used.
Assuntos
Azul de Metileno/sangue , Ácido Úrico/sangue , Aerobiose , Alantoína/sangue , Anaerobiose , Cromatografia Líquida de Alta Pressão , Humanos , Peróxido de Hidrogênio/sangue , Oxirredução , Fatores de TempoRESUMO
A 2% aqueous solution of methylene blue was administered as a single intravenous (i.v.) bolus injection (10 mg/kg) to six lactating cows and seven lactating goats and a continuous i.v. drip to five lactating goats. The same dose was administered as a 10% solution by intramammary infusion to five lactating goats. Blood and milk samples collected at various times after these treatments were assayed for the drug by a colorimetric method. Methylene blue, a highly charged molecule (pKa less than or equal to 1), passed readily from blood into milk; drug concentrations in milk 4-36 h after the single i.v. bolus injection were higher than those in blood. When examined at constant methylene blue levels in blood, a milk--blood ratio of 5:1 was observed. After intramammary infusion, the drug passed quickly into systemic circulation, peaked at 3 h and was still detectable in blood 12 h after infusion. The drug appeared in the urine within 15 min after intramammary infusion. The rapid movement of the drug across the blood--milk barrier cannot be explained on the basis of its known physicochemical properties or according to the pH--pKa passive diffusion concept.
