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E Shefter

Publications and source records attributed to E Shefter.

51 records · Page 3Linked to original sources
PubMed1968

Crystal structure of a complex of acridine, cytosine and water (1:1:1).

X-ray structural analysis of a crystalline complex between acridine C(13)H(9)N, cytosine C(4)H(5)N(3)O, and water (1:1:1) has been completed. The cytosine and water molecules form a sheet-like structure through a series of hydrogen bonds. The acridine molecules are bound to this layer through a hydrogen bridge from the water to the ring nitrogen. The acridine molecules stack in a parallel fashion normal to the cytosine-water sheets, with an average interplanar spacing of 3.5 angstroms.

Acridines↗
PubMed1966

Crystal and molecular structure of acetylselenocholine iodide.

The structure of acetylselenocholine iodide has been determined by x-ray crystallographic analysis. The molecule is in the trans conformation about the C-C bond of the choline residue. This conformation appears to explain the molecule's inability to give a positive cholinergic response when added to an electroplax preparation.

Chemical Phenomena↗
PubMedDate not supplied

Oral and rectal nalbuphine bioavailability: first-pass metabolism in rats and dogs.

The disposition of the narcotic antagonist/analgesic nalbuphine after i.v., oral, and rectal dosing was evaluated in rats and dogs. In both species nalbuphine had high systemic clearance and low oral bioavailability as a result of extensive first-pass metabolism. Administration to a closed 2 cm length of rectum in rats resulted in complete bioavailability; first-pass metabolism was circumvented. However, the extent of first-pass metabolism increased when the dose was not restricted to the lower rectum. Rectal nalbuphine bioavailability in dogs from a solution or three suppository formulations was low and equivalent to oral bioavailability. This was probably because of upward spreading of the dose and subsequent first-pass metabolism. Sodium salicylate, which has been shown to improve rectal absorption of other drugs, did not affect nalbuphine bioavailability rectally.

Administration, Oral↗
PubMedDate not supplied

Phenylpropanolamine pharmacokinetics in dogs after intravenous, oral, and oral controlled-release doses.

An adaption of a published high performance liquid chromatographic (HPLC) assay for phenylpropanolamine (PPA) in plasma was used to examine PPA pharmacokinetics in dogs. Plasma was extracted into ethyl acetate after the addition of 3.5 per cent sodium carbonate, and was then back-extracted into aqueous acetic acid. The acetic acid was injected onto a cyano column using a mobile phase of acetonitrile, dilute hydrochloric acid, and sodium heptane sulfonate. Detection was by UV absorbance at 210 nm. The relative standard deviation of replicate assays averaged 5.2 per cent over a concentration range of 50-1750 ng ml-1 plasma. PPA extraction recovery exceeded 90 per cent. The limit of detection was 30 ng ml-1 using 0.5 ml plasma and injecting 10 microliter. PPA disposition was characterized in three dogs administered PPA i.v. and orally in immediate-release and controlled-release formulations. The terminal elimination half-life averaged 3.5 +/- 0.5 h after the i.v. dose. Oral absorption from the immediate-release capsule was rapid and bioavailability was 98.2 +/- 6.9 per initial rapid cent. PPA absorption from the controlled-release dosage form was biphasic; an rapid phase was followed by a second, slower absorption phase which continued over 16 h. Plasma PPA concentrations then declined with a half-life roughly parallel to the i.v. and oral immediate-release half-lives. Oral bioavailability from the controlled release tablet was 93.7 +/- 5.9 per cent.

Administration, Oral↗