The mechanism by which quinidine affects hepatic digoxin pharmacokinetics remains controversial. Here, we study the role of displacement of digoxin from hepatic sinusoidal binding sites by quinidine. We used the impulse–response technique in the single-pass perfused rat liver to describe the digoxin hepatic disposition by a physiologically-based pharmacokinetic liver model. The impulse–response study involved analysis of outflow curves following two consecutive doses of digoxin (42 and 125μg) without and with quinidine (10μM) in perfusate. In addition, the effect of quinidine on digoxin binding in liver subcellular fractions was quantified. Quinidine increased the peak outflow concentration for digoxin at the low digoxin dose but not at the high dose. This increase could be adequately described when digoxin displacement from sinusoidal and intrahepatic binding sites was included in the model. Inhibition of digoxin binding by quinidine was also observed in vitro. The decrease of biliary excretion of digoxin by quinidine was accompanied by a linear increase in sinusoidal efflux of digoxin’s primary metabolite, digoxigenin bisdigitoxoside (Dg2). In contrast to biliary excretion, inhibition of sinusoidal uptake may become dominant only for high concentrations of quinidine.
Publication date:
Available online 6 May 2013
Source:Current Opinion in Chemical Biology Author(s): Miao Wen , Brooks B Bond-Watts , Michelle CY Chang Commercial fermentation processes have long taken advantage of the synthetic power of living systems to rapidly and efficiently tra ... more
Publication date:
Available online 9 May 2013
Source:Current Opinion in Chemical Biology Author(s): Chan Hyuk Kim , Jun Y Axup , Peter G Schultz The site-specific incorporation of unnatural amino acids with orthogonal chemical reactivity into proteins enables the synthesis of struc ... more
Publication date:
Available online 8 May 2013
Source:Current Opinion in Chemical Biology Author(s): David A Rothamer , Timothy J Donohue From the inception of internal combustion engines, biologically derived fuels (biofuels) have played a role. Nicolaus Otto ran a predecessor to to ... more
Regular marijuana use is associated with favorable indices related to diabetic control, say investigators. They found that current marijuana users had significantly lower fasting insulin and were less likely to be insulin resistant, even after excluding patients with a diagnosis of diabetes ... more
Most children who suffer from sports-related concussions recover within a few days. However, in a small number of children, symptoms can last for a month or more. Although there have been numerous theories as to what might predict a longer recovery time, there is no definitive answer as to ... more
Although mammography, the gold standard of breast cancer screening, reduces breast cancer mortality, it has important limitations. Critics point to reduced sensitivity for women with dense breasts, a high rate of false positives leading to excessive biopsies, and concerns about long-term ef ... more