Blood-brain barrier transport of opioid analgesics

Opioid analgesics exhibit cationic properties under physiological conditions, and the mechanism underlying permeation of the blood-brain barrier thus cannot be fully explained by simple diffusion alone. Various types of transporters that exhibit substrate specificity are localized on the blood-brain barrier, and play a role in transporting substances from circulating blood and from brain interstitial fluid. Progress is being made in explaining the mechanisms, functions, and physiological roles of polyspecific organic cation transporters, but little evidence has indicated that these previously identified organic cation transporters are involved in the transport of opioid analgesics across the blood-brain barrier. Consequently, clarifying the role of transporters in the distribution of opioid analgesics into the brain and determining their transport molecule will not only provide clues to effective drug delivery to the brain, but will also contribute to optimizing pain relief treatment, and by extension play a role in drug discovery for analgesics. Currently there are enthusiastic discussions in the literature regarding the existence of putative transporters involved in the transport of opioid analgesics across the blood-brain barrier. This review article introduces the results of our research as well as recent findings on the involvement of transporters in the blood-brain barrier transport of opioid analgesics such as morphine, morphine metabolites, oxycodone, fentanyl, codeine, and pentazocine.     

Myocardial fibrosis attenuates the effect of cibenzoline on left ventricular diastolic function in patients with hypertrophic cardiomyopathy

The aim of this study was to investigate the relationship between late gadolinium enhancement (LGE) and the effect of cibenzoline (CBZ) on left ventricular (LV) diastolic function in hypertrophic cardiomyopathy (HCM) patients. Echocardiography before and after intravenous CBZ (1.4 mg/kg over 5 minutes) and magnetic resonance imaging (MRI) were performed in 22 consecutive patients with HCM [mean age: 65 ± 14 years, obstructive HCM: 14, nonobstructive HCM (HNCM): 8]. The extent of LGE (%LGE = LGE volume/total LV volume) was obtained by contrast-enhanced MRI using custom software. LGE was observed in 19 patients (mean %LGE = 5.1% ± 3.9%). The propagation velocity of LV early filling flow (Vp) increased significantly in patients with obstructive HCM (26 ± 7 to 36 ± 14 cm/s, P = 0.001) and nonobstructive HCM (25 ± 9 to 36 ± 16 cm/s, P = 0.007). A significant negative correlation was observed between the change in Vp and %LGE in patients with HCM (r = 20.542, P = 0.009). Less extensive myocardial fibrosis, as demonstrated by LGE on contrast-enhanced MRI, may predict the ability of CBZ to improve LV diastolic function in HCM.     

P-glycoprotein mediates brain-to-blood efflux transport of buprenorphine across the blood-brain barrier

The involvement of P-glycoprotein (P-gp) in buprenorphine (BNP) transport at the blood-brain barrier (BBB) in rats was investigated in vivo by means of both the brain uptake index technique and the brain efflux index technique. P-gp inhibitors, such as cyclosporin A, quinidine and verapamil, enhanced the apparent brain uptake of [3H]BNP by 1.5-fold. The increment of the BNP uptake by the brain suggests the involvement of a P-gp efflux mechanism of BNP transport at the BBB. [3H]BNP was eliminated with an apparent elimination half-life of 27.5 min after microinjection into the parietal cortex area 2 regions of the rat brain. The apparent efflux clearance of [3H]BNP across the BBB was 0.154 ml/min/g brain, which was calculated from the elimination rate constant (2.52 x 10- 2 min- 1) and the distribution volume in the brain (6.11 ml/g brain). The efflux transport of [3H]BNP was inhibited by range from 32 to 64% in the presence of P-gp inhibitors. The present results suggest that BNP is transported from the brain across the BBB via a P-gp-mediated efflux transport system, at least in part.     

Video-assisted thoracoscopic surgery for pleuroperitoneal communication

Here we report the cases of five patients on continuous ambulatory peritoneal dialysis (CAPD) who developed hydrothorax because of pleuroperitoneal communication. Preoperative computed tomography (CT) peritoneography revealed penetrated sites on the diaphragm in all patients. All patients underwent video-assisted thoracoscopic surgery (VATS), and a dialysate containing indigo carmine was injected intraperitoneally through a CAPD catheter to confirm the fistula. In all patients, a thinned bleb was found at the center of the diaphragmatic tendon consistent with that noted on preoperative CT peritoneography. The bleb was resected using a surgical stapler in four patients, and the pleuroperitoneal communication did not recur. However, in one patient, the bleb was only covered with reinforcement agents and the hydrothorax recurred after CAPD. This study demonstrates that VATS treatment for pleuroperitoneal communication is safe and effective but that lesion resection would be more useful for preventing hydrothorax recurrence in patients undergoing CAPD.     

Lingular-segment torsion after extended left-upper division segmentectomy by video-assisted thoracic surgery with indocyanine green fluorescence imaging

Lingular-segment torsion after left-upper division segmentectomy (LUDS) is a rare complication, and the cause remains unclear. Here we report the case of a patient who developed lingular-segment torsion after LUDS for multiple lung metastases of breast cancer. One lung nodule was located in the S1 + 2 segment and another between the upper lobe and S6 on an incomplete interlobar fissure. The lung metastases were resected by extended LUDS using video-assisted thoracic surgery with indocyanine green fluorescence imaging. The staple line on the lingular segment was vertically tilted against the interlobar line because of the atypical defect of the fluorescence plane and nodule position. Chest X-ray and contrast-enhanced computed tomography indicated ischemia and torsion of the lingular segment on the second postoperative day, and completion of lingular segmentectomy was performed. This case showed the vertical intersegment staple line during LUDS was one of the important causes of postoperative torsion of the lingular segment.