We compared the potency and inhibitory actions of three different classes of organic acids on a Cl channel derived from colonic enterocyte plasma membrane vesicles. Chloride channels were incorporated into planar lipid bilayer membranes to examine the effects of the anthranilic acids, diphenylamine 2-carboxylic acid (DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), the indanyl alkanoic acids, 2-[(2-cyclopentyl-6,7-dichloro-2,3-dihydro-2-methyl-1-oxo-1H-inden -5-yl)oxy] acetic acid (IAA-94) and its stereoenantiomer IAA-95, and the disulfonic stilbene, 4,4'-dinitro-stilbene-2,2'-disulfonic acid (DNDS). Except for DNDS, each of the blockers was equipotent from both the outer membrane and the cytoplasmic side of the channel protein. The potency order from the outmembrane side was DNDS greater than IAA-94 = IAA-95 greater than NPPB much greater than DPC. In contrast, the potency order from the cytoplasmic side was IAA-94 = IAA-95 greater than NPPB greater than DNDS much greater than DPC. DPC and NPPB caused a concentration-dependent decrease in the single-channel conductance (fast block). DNDS, IAA-94, and IAA-95 caused a flickery-type block and a concentration-dependent decrease in open-channel probability. Kinetic analysis revealed that blockade could be explained by a linear closed-opened-blocked kinetic scheme. Similarities in the electrostatic potential maps of these open-channel blockers suggest they may bind to a single shared binding site within the channel protein.

background: An enteric-coated levonorgestrel emergency contraceptive pill (E-LNG-ECP) is an improved formulation, in terms of side effects, which both dissolves and is absorbed in the intestine. Our aim was to evaluate the efficacy and safety of E-LNG-ECP as an over-the-counter (OTC) drug for emergency contraception (EC) in Chinese women.methods: A Phase IV clinical trial was conducted in five family planning clinics in China. Women seeking EC within 72 h after unprotected sexual intercourse or contraceptive failure who met the inclusion criteria were recruited. The efficacy of contraception (primary end-point was pregnancy rate), side effects (i.e. safety) and the value of E-LNG-ECP for EC were investigated.results: Of 2445 women (aged 15 -48 years) who took E-LNG-ECP with follow-up to determine pregnancy, only five pregnancies (0.2%) occurred. The efficacy of contraception was 95.3%. In total, 6.5% of women reported at least one adverse event after taking E-LNG-ECP, and no serious adverse events were reported. Only four subjects (0.16%) reported vomiting. The incidence of menstrual cycle disturbance was 20.1% after taking E-LNG-ECP. Subjects who had previously taken ECPs (54.4% of these women) rated the acceptability of E-LNG-ECP at 9.36 (on a 10-point scale) higher (P , 0.05) than the rating of other LNG-EC pills taken previously.conclusions: The study found that E-LNG-ECP was effective, safe and well tolerated as an OTC drug. However, an randomized controlled trial should be performed to compare standard LNG tablets with E-LNG-ECP.