Correlates of Nine-Month Retention following Interim Buprenorphine-Naloxone Treatment in Opioid Dependence: A Pilot Study.

Interim medication-only treatment has been suggested for the initiation of opioid maintenance treatment (OMT) in opioid-dependent subjects, but this rarely has been studied using buprenorphine instead of methadone. Following a pilot trial assessing interim buprenorphine-naloxone treatment in order to facilitate transfer into OMT, we here aimed to study retention, and potential correlates of retention, in full-scale treatment. Thirty-six patients successfully referred from a waiting list through an interim treatment phase were followed for nine months in OMT. Baseline characteristics, as well as urine analyses during the interim phase and during full-scale OMT, were studied as potential correlates of retention. The nine-month retention in OMT was 83 percent (n = 30). While interim-phase urine samples positive for benzodiazepines did not significantly predict dropout from full-scale OMT (p = 0.09), urine samples positive for benzodiazepines within full-scale OMT were significantly associated with dropout (p < 0.01), in contrast to other substances and baseline characteristics. Retention remained high through nine months in this pilot study sample of patients referred through buprenorphine-naloxone interim treatment, but use of benzodiazepines is problematic, and the present data suggest that it may be associated with treatment dropout.

Investigating the potential role of multi-drug resistance protein (MRP) transporters in fetal to maternal glyburide efflux in the human placenta.

Glyburide, a drug used to treat gestational diabetes has previously been shown not to be measurable in fetal blood, and to be transferred from the fetal to the maternal circulation against a concentration gradient. The objective of the study is to determine whether indomethacin, an inhibitor of the multi-drug resistance family (MRP) of transporters is involved in the active efflux of glyburide from the fetus to the mother. Using the dually perfused human placental cotyledon model, 12 perfusions were performed of both glyburide and indomethacin concomitantly. The rate of transfer of glyburide in the presence of inhibitor was not different from the rate of transfer of glyburide in the absence of inhibitor. Furthermore, our study suggests that MRP1, 2 or 3 may be only minimally involved in the transport of glyburide across the human placenta. These results pose other ABC transporters, such as likely candidates for the placental transfer of glyburide.

Breast cancer resistance protein: mediating the trans-placental transfer of glyburide across the human placenta.

Members of the ATP-binding cassette (ABC) efflux transporter family, including P-glycoprotein (PGP), the multidrug resistance-associated proteins (MRPs) and the breast cancer resistance protein (BCRP) have been shown to be highly expressed in the human placenta. Recent studies documented that the oral hypoglycemic glyburide does not cross the human placenta to an appreciable extent. Furthermore, the trans-placental transfer of glyburide has been shown not to be affected by either the presence of PGP inhibitor, verapamil or MRP inhibitor, indomethacin. Therefore, our objective was to identify other human placental ABC transporters potentially involved in limiting the trans-placental transfer of glyburide to the fetus. [(3)H]-glyburide transport was examined in brush border human placental vesicles in the presence or absence of specific inhibitors. Prepared vesicles were 70% oriented right-side-out and demonstrated 25-27 fold enrichment as compared to whole placenta. Functional studies demonstrated significant increases in the intra-vesicular accumulation of [(3)H]-glyburide in vesicles treated with the BCRP inhibitor, novobiocin. In contrast, PGP inhibition as well as MRP inhibition did not affect [(3)H]-glyburide accumulation. This is the first evidence to clearly indicate that glyburide is preferentially transported by BCRP, in the brush border of the human placenta. Our study also indicates that BCRP likely effluxes substrates in the fetal to maternal direction in the human placenta.

Plasmid size up to 20 kbp does not limit effective in vivo lung gene transfer using compacted DNA nanoparticles.

Nanoparticles consisting of single molecules of DNA condensed with polyethylene glycol-substituted lysine 30-mers efficiently transfect lung epithelium following intrapulmonary administration. Nanoparticles formulated with lysine polymers having different counterions at the time of DNA mixing have distinct geometric shapes: trifluoroacetate or acetate counterions produce ellipsoids or rods, respectively. Based on intracytoplasmic microinjection studies, nanoparticle ellipsoids having a minimum diameter less than the 25 nm nuclear membrane pore efficiently transfect non-dividing cells. This 25 nm size restriction corresponds to a 5.8 kbp plasmid when compacted into spheroids, whereas the 8-11 nm diameter of rod-like particles is smaller than the nuclear pore diameter. In mice, up to 50% of lung cells are transfected after dosing with a rod-like compacted 6.9 kbp lacZ expression plasmid, and correction of the CFTR chloride channel was observed in humans following intranasal administration of a rod-like compacted 8.3 kbp plasmid. To further investigate the potential size and shape limitations of DNA nanoparticles for in vivo lung delivery, reporter gene activity of ellipsoidal and rod-like compacted luciferase plasmids ranging in size between 5.3 and 20.2 kbp was investigated. Equivalent molar reporter gene activities were observed for each formulation, indicating that microinjection size limitations do not apply to the in vivo gene transfer setting.

Transport of glyburide by placental ABC transporters: implications in fetal drug exposure.

Much evidence has demonstrated that a number of ATP-binding cassette (ABC) efflux transporters including P-glycoprotein (PGP), the multidrug resistance-associated proteins (MRPs) and the breast cancer resistance protein (BCRP) are highly expressed in placental tissues and are believed to profoundly limit the passage of therapeutic or toxic xenobiotics to the fetus. Recent studies indicate that the oral hypoglycemic glyburide does not cross the human placenta to an appreciable extent. Our objective was to identify placental transporters potentially involved in limiting the transplacental transfer of glyburide to the fetus. Thus, [(3)H]-glyburide transport was examined in BCRP, PGP, MRP1, MRP2 and MRP3 over-expressing cell lines in the presence or absence of specific inhibitors. Our results demonstrated significant increases in the intracellular accumulation of [(3)H]-glyburide in BCRP and MRP3 over-expressing cells in the presence of the inhibitors novobiocin and indomethacin, respectively. PGP inhibition with verapamil or MRP inhibition with indomethacin did not affect [(3)H]-glyburide accumulation in the PGP or MRP2 over-expressing cell lines and only limited changes were seen in the MRP1 over-expressing cell line. On the other hand, glyburide was found to significantly inhibit MRP1-, MRP2- and MRP3-mediated efflux of 5-carboxyfluorescein diacetate and PGP-mediated transport of rhodamine 123. Our evidence is the first to clearly indicate that glyburide is preferentially transported by BCRP and MRP3.

Designing pregnancy centered medications: drugs which do not cross the human placenta.

This review considers and evaluates the role of placental transporters (multidrug resistance proteins, P-glycoprotein and breast cancer resistance protein) in the uptake and efflux of drugs used in pregnancy. The effect of placental transporters in effluxing drugs such as glyburide and numerous protease inhibitors from the fetal circulation offers the potential to manipulate the passage of drugs across the placenta. The discovery of the interactions of these drugs with placental transporters may provide a novel framework for future drug development in which medications can be designed to control the degree of fetal exposure and thus prevent fetal risk.

Evidence for a H+ nitrate symporter in Aspergillus nidulans.

Nitrate transport in Aspergillus nidulans was dependent upon a consistent proton motive force (delta p) across the cell membrane which was maintained in a range of 105 (+/- 6.7) to 131 (+/- 3.4) mV over an external pH span of 5.5 to 7.5. The membrane potential (delta psi) measured by uptake of [3H]-tetra-phenylphosphonium bromide and the transmembrane pH difference (delta pH) measured by the distribution of 3H2O and [14C]- salicylic acid were used to compute the delta p present during transport of nitrate. Energy dependent accumulation of nitrate was measured in actively assimilating and tungstate inhibited cells. A delta G for nitrate of 14 kJ mol-1 was computed from the results. Cells induced for nitrate transport maintained internal nitrate levels of 6 to 8 mM based on an internal volume of 2.6 microliters/mg dry wt as determined by a conventional dual label procedure. A fivefold higher level of cellular nitrate was observed in tungstate inhibited cells. Nitrate accumulation was dependent upon a H+ gradient which was dissipated by treatment with 2-butanol, the ionophores valinomycin and gramicidin and the proton conductors carbonyl cyanide m-chlorophenyl hydrazone and N,N'-dicyclo-hexylcarbodiimide. Significant ATP and nitrate efflux occurred in cells treated with the above agents. The results suggest that nitrate is transported by symport with H+ on a carrier which is functionally linked to a H+ ATPase pump.