PEG absorption

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this is in the files section under urinary excretion of PEG

butquestions have recently been raised about the degreeof absorption and the potential for toxicity, particularly for PEG, due to the large amounts of thesesolutions administered during gut lavage (9,10).After oral ingestion of 1-10 g of PEG 3350 (dosesused as a nonabsorbable marker), from 96.3% to10Q.l% is recovered in the feces (3,4,11). Thus, at"most; only a small fraction of orally ingested PEG isabsorbed. However, gut lavage with PEG-ELSentailsingestion of about 240 g of PEG 3350; if only 3%-4%diffused across the mucosa, a substantial quantity ofPEG would be absorbed into the body. It would bedifficult, if Dot impossible, to accurately assess theabsorption of up to 3% of ingested PEGby

measuringrecovery of PEGin the stool. The difference between97% and 100% fecal recovery cannot be accuratelydetected by the analytical methods, and stool recovery is usually not exactly 100%. even under the bestof experimental conditions. We therefore decided toassess absorption by measuring recovery in theurine, which is made possible by the fact that 85%and 96% of PEG 1000 and

6000, respectively, areexcreted in the urine after intravenous administration (12). After oral administration of 5 g of PEG3350, et al. (13) found its 24-h urinaryexcretion to be 1.26% in normal subjects and 2.88%in patients with eczema. This would imply thatpatients could absorb 3-7 g of PEG after ingesting 4L of PEG-ELScontaining 240 g of PEG. However, thestudy by et al. (13) may not be comparable toconditions that occur during lavage of the gastrointestinal tract at rapid rates of ingestion or intragastricinstillation with large amounts of PEG-ELS.Although sulfate is considered to be a poorlyabsorbed anion (7,8), absorption has been demonstrated from the rodent small intestine (14), andbetween 2% and 4% of sulfate is absorbed from theperfused human colon (15). In addition, 74%--83%oftracer doses of orally

administered radioactive sulfate have been recovered in the urine of humans (16).Four liters of PEG-ELS contains 320 mEq of sulfateand, using reasoning similar to that for PEG, a largequantity of sulfate could be absorbed. Sulfate excretion occurs mainly via the kidney, with tubularreabsorption being the dominant renal regulatorymechanism at normal plasma levels (17). With increasing loads. sulfate excretion approaches glomerular filtration asymptotically because tubular reabsorption is rapidly exceeded (17). In human studies,urinary

excretion of sulfate was between 60% and65% during steady state intravenous sodium sulfateinfusion (18), and between 80% and 95% after intravenously administered radioactive sulfate tracer(16,19). Using the same principle as for PEG. we alsoassessed sulfate absorption, as any appreciableamount absorbed during gut lavage with PEG-ELSshould be reflected by increased urinary sulfateexcretion.MateriHistologically abnormal intestinal mucosa may be more permeable to PEG oflarger molecular weight (13.25). However. increasedabsorption of PEG 3350was not found in our inflammatory bowel patients or during perfusion of dis-.

eased colon (4). Additional investigation is indicatedto further define the influence of abnormal intestinalmucosa on PEG 3350 absorption during administration of PEG-ELS.Available animal data support the contention that http://f1.grp.yahoofs.com/v1/0FtXT22LVc9TslDlxrGA5NoKmZkvShlnEBg1ybW5FXcxOWsBUIyirSosXFOMYFHCQ30eS3hnqzF90ZTyWN3Mew/Urinary%20excretion%20of%20PEG%203350.pdf