New polyethylene glycol laxative for treatment of constipation in adults: a randomized, double-blind, placebo-controlled study.

BACKGROUND: This study evaluated the safety and effectiveness of a new polyethylene glycol (PEG) laxative (MiraLax, Braintree Laboratories Inc, Braintree, Mass) in 23 patients reporting a history of constipation. METHODS: After a 7-day placebo control period, patients were randomized into a double crossover trial of placebo versus 17 g of PEG daily for 4 days. Patient maintained a stool diary. RESULTS: Daily ingestion of a 17 g dose of PEG increased mean daily bowel movement frequency to once per day by the last 7 days of the 14-day treatment period. This was a statistically significant improvement over placebo, which provided about 1 bowel movement every 2 days during the last week of therapy. Patient diary ratings of related subjective symptoms were improved with PEG treatment over placebo. Both investigator and patients rated PEG therapy superior to placebo. No clinically significant changes in blood chemistry, complete blood count (CBC), or urinalysis were observed. CONCLUSIONS: Daily therapy with 17 g of PEG laxative for 14 days resulted in a significant improvement in bowel movement frequency in constipated patients relative to placebo by the second week of treatment.

Structure-function relationships for a voltage-dependent ion channel: properties of COOH-terminal fragments of colicin E1.

The effects on planar lipid bilayer membranes of carboxyl-terminal fragments derived from the bacteriocin colicin E1 by either proteolysis or CNBr cleavage are indistinguishable from those of the voltage-dependent parent colicin molecule. An upper limit to the length of the COOH-terminal peptide required for channel formation is 152 amino acid residues from the COOH-terminal end, as indicated by the CNBr fragment. In addition, use of carboxypeptidase shows that the COOH-terminal end of the molecule remains on the side of the membrane to which it was added. COOH-terminal peptides of colicin E1 spontaneously associate with oil or hexane droplets in an aqueous system and remain at the interface between the two phases to a significantly greater degree than other colicin E1 fragments or cytochrome c. These results, together with the amino acid sequence, suggest a model wherein the colicin E1 channel is formed first by spontaneous attachment to a membrane of an alpha-helical hairpin centered at a 35-residue hydrophobic region near the COOH-terminal end. Application of a potential of the correct polarity then facilitates a major conformational change in the protein, allowing insertion of the remainder of the COOH-terminal end to form the open channel.