Aims The purpose of this in vivo human study was to assess the effect of altered gastric emptying and gastrointestinal motility on the absorption of metformin in healthy subjects. Methods An open-label, three treatment, three period crossover study was conducted in 11 healthy volunteers. Each subject received 550 mg metformin hydrochloride in solution alone; 5 min after a 10 mg i.v. dose of metoclopramide; and 30 min after a 30 mg oral dose of propantheline. Metformin solution was radiolabeled by the addition of 99m Tc-DTPA. The gastrointestinal transit of the solution was monitored by gamma scintigraphy and the pharmacokinetic data were correlated with the scintigraphic ®ndings. Results Scintigraphic data indicated that pretreatment with metoclopramide decreased gastric emptying time and increased gastrointestinal motility while pretreatment with propantheline had the opposite effect. The systemic disposition of metformin was not altered by pretreatment with metoclopramide and propantheline, as judged by unchanged renal clearance and elimination half-life of metformin. Extent of metformin absorption was essentially unchanged after pretreatment with metoclopramide. However, AUC(0,?) and % UR (percent dose excreted unchanged in urine) generally increased with increase in gastric emptying time and small intestinal transit times. GI overlay plots showed that the absorption phase of metformin plasma pro®le always coincided with gastric emptying and the beginning of decline of metformin plasma concentrations was usually associated with the colon arrival. Only in cases where the intestinal transit was drastically prolonged by propantheline pretreatment, was a decline in plasma levels observed prior to colon arrival. Conclusions Metformin is primarily absorbed from the small intestine. The extent of metformin absorption is improved when the gastrointestinal motility is slowed. These ®ndings have signi®cant implications in the design of a metformin modi®ed release dosage form.

Fosinoprilat, the active product of fosinopril, is eliminated by a hepatic pathway, in addition to the renal pathway shared by other angiotensin converting enzyme inhibitors. Congestive heart failure (CHF) may elevate drug plasma concentrations caused by a reduction in steady-state volume of distribution (Vss) and/or an impairment of clearance. This study compared the pharmacokinetics and pharmacodynamics of fosinopril (intravenous and oral) in 10 patients with established CHF and 10 age-, sex-, and weight-matched normal control subjects. There were no statistically significant differences between the patients with CHF and the control patients with respect to maximum drug concentration (Cmax) or area under the plasma concentration-time curve from 0 to infinity. Absolute bioavailability was approximately 29%. Vss was similar, and protein binding was 99% in both groups. The oral half-life of fosinoprilat was significantly longer than the intravenous half-life for both the patients with CHF and normal subjects, without statistically significant differences between the study groups. Median time to reach Cmax occurred at 4 hours in each group and corresponded to maximum angiotensin converting enzyme inhibition, which was essentially complete through 12 hours and markedly reduced through 24 hours. Thus these data indicate that patients with CHF can receive fosinopril without undue increases in fosinoprilat concentrations. This probably is due to the dual excretory pathways.

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