MEB may be a useful probe to assess how altered hepatic function at the transport level modulates hepatobiliary drug disposition.

Joint hypermobility syndrome (JHS) and Ehlers-Danlos syndrome, hypermobility type (EDS-HT) are two clinically overlapping connective tissue disorders characterized by chronic/recurrent pain, joint instability complications, and minor skin changes. Fatigue and headache are also common, although are not yet considered diagnostic criteria. JHS/EDS-HT is a unexpectedly common condition that remains underdiagnosed by most clinicians and pain specialists. This results in interventions limited to symptomatic and non-satisfactory treatments, lacking reasonable pathophysiologic rationale. In this manuscript the fragmented knowledge on pain, fatigue, and headache in JHS/EDS is presented with review of the available published information and a description of the clinical course by symptoms, on the basis of authors' experience. Pathogenic mechanisms are suggested through comparisons with other functional somatic syndromes (e.g., chronic fatigue syndrome, fibromyalgia, and functional gastrointestinal disorders). The re-writing of the natural history of JHS/EDS-HT is aimed to raise awareness among clinical geneticists and specialists treating chronic pain conditions about pain and other complications of JHS/EDS-HT. Symptoms' clustering by disease stage is proposed to investigate both the molecular causes and the symptoms management of JHS/EDS-HT in future studies.

Determining the biliary clearance of drugs in humans is very challenging because bile in not readily accessible due to the anatomy of the hepatobiliary tract. The collection of bile usually is limited to post-surgical patients with underlying hepatobiliary disease. In healthy subjects, feces typically are used as a surrogate to quantify the amount of drug excreted via non-urinary pathways. Nevertheless, it is very important to characterize hepatobiliary elimination because this is a potential site of drug interactions that might result in significant alterations in systemic or hepatic exposure. In addition to the determination of in vivo biliary clearance values of drugs, the availability of in vitro models that can predict the extent of biliary excretion of drugs in humans may be a powerful tool in the preclinical stages of drug development. In this review, recent advances in the most commonly used in vivo methods to estimate biliary excretion of drugs in humans are outlined. Additionally, in vitro models that can be employed to investigate the molecular processes involved in biliary excretion are discussed to present an updated picture of the new tools and techniques that are available to study the complex processes involved in hepatic drug transport.

The biliary clearance (Cl(biliary)) of three compounds was estimated using sandwich-cultured human hepatocytes (SCHH) and compared with Cl(biliary) values measured in vivo. Tc-99m sestamibi (MIBI) Cl(biliary) was determined in seven healthy volunteers using an oroenteric catheter to aspirate duodenal secretions, and gamma scintigraphy to determine gallbladder contraction; this technique was used previously to determine Tc-99m mebrofenin (MEB) and piperacillin (PIP) in vivo Cl(biliary). In vitro Cl(biliary) of MEB, MIBI, and PIP was quantified in SCHH as the ratio of mass excreted into bile canaliculi and area under the blood concentration-time curve (AUC) in medium. MIBI Cl(biliary) in vivo was 5.5+/-1.2 mL/min/kg (mean+/-SD). The rank order of Cl(biliary) predicted from SCHH corresponded well with the in vivo Cl(biliary) values in mL/min/kg for MEB (7.44 vs 16.1), MIBI (1.20 vs 5.51), and PIP (0.028 vs 0.032). In conclusion, the methods developed allowed for reproducible quantification of Cl(biliary) of drugs in healthy humans and prediction of Cl(biliary) from in vitro data.

Biliary excretion is an important route of elimination and the biliary tract is a potential site of toxicity for many drugs and xenobiotics. Quantification of biliary excretion in healthy human volunteers is logistically challenging and is rarely defined during drug development. The current study uses a novel oroenteric tube coupled with a specialized clinical protocol to examine the pharmacokinetics of 99m Technetium (Tc-99m) mebrofenin, a compound that undergoes rapid hepatic uptake and extensive biliary excretion. A custommade multilumen oroenteric tube was positioned in the duodenum of healthy human volunteers. Subjects were positioned under a gamma camera and 2.5 mCi of Tc-99m mebrofenin was administered intravenously. Duodenal aspirates, blood samples, and urine were collected periodically for 3 hours. Two hours after Tc-99m mebrofenin administration, the gallbladder was contracted with an intravenous infusion of cholecystokinin-8. Gamma scintigraphy was used to determine the gallbladder ejection fraction in each subject. Total systemic clearance of Tc-99m mebrofenin approximated liver blood flow (Cl total 17.3 ± 1.7 mL/min/kg), and 35% to 84% of the Tc-99m mebrofenin dose was recovered in bile. However, when the data were corrected for the gallbladder ejection fraction, 71% to 92% of the excreted Tc-99m mebrofenin dose was recovered. This novel oroenteric tube and clinical protocol provide a useful method to quantify biliary excretion of xenobiotics in healthy human volunteers.

A semiphysiologically based pharmacokinetic (semi-PBPK) model was developed to describe a unique blood, liver, and bile clinical data set for the hepatobiliary imaging agent 99mTechnetium–mebrofenin (99mTc–mebrofenin), and to simulate sites/mechanisms of a 99mTc–mebrofenin–ritonavir drug–drug interaction (DDI). The transport inhibitor ritonavir (multiple-dose: 2 × 300 mg) significantly increased systemic 99mTc–mebrofenin exposure as compared with control (4,464 ± 1,861 vs. 1,970 ± 311 nCi min/ml; mean ± SD), without affecting overall hepatic exposure or biliary recovery. A novel extrahepatic distribution compartment was required to characterize 99mTc–mebrofenin disposition. Ritonavir inhibited 99mTc–mebrofenin accumulation in human sandwich-cultured hepatocytes (SCH) (half maximal inhibitory concentration (IC50) = 3.46 ± 1.53 µmol/l). Despite ritonavir accumulation in hepatocytes, intracellular binding was extensive (97. 6%), which limited interactions with multidrug resistance protein 2 (MRP2)-mediated biliary excretion. These in vitro data supported conclusions from modeling/simulation that ritonavir inhibited 99mTc–mebrofenin hepatic uptake, but not biliary excretion, at clinically relevant concentrations. This integrated approach, utilizing modeling, clinical, and in vitro data, emphasizes the importance of hepatic and extrahepatic distribution, assessment of inhibitory potential in relevant in vitro systems, and intracellular unbound concentrations to assess transporter-mediated hepatic DDIs.

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AimTo evaluate the applicability of a novel method to determine the biliary excretion of piperacillin. MethodsHealthy volunteers were administered piperacillin i.v. Duodenal aspirates were collected via a custom-made oroenteric catheter; blood and urine also were collected. Gallbladder ejection fraction (EF) was determined by gamma scintig raphy and pharmacokinetic parameters were calculated using noncompartmental analysis. ResultsThe fraction of the piperacillin dose excreted unchanged into bile was 1.1 ± 0.3% (biliary clearance corrected for EF was 0.032 ± 0.008 ml min − 1 kg − 1 ). ConclusionsThis methodology can be used to determine reliably the biliary clearance of drugs that are excreted only marginally into bile. Normalization of biliary clearance for EF significantly reduces intersubject variability of this parameter.