Gastric emptying in patients with insulin dependent diabetes mellitus and bioavailability of thioctic acid-enantiomers

The objective of this study was to determine the impact of prolonged gastric emptying in patients with insulin dependent diabetes mellitus (IDDM) on the bioavailability of the R (+)- and S (−)-thioctic acid (TA) enantiomers. Gastric emptying time (GET) was assessed in 30 healthy volunteers and 22 patients with IDDM using sequential ultrasonography after a standardized solid-liquid test meal. Pharmacokinetics and absolute bioavailability ( F ) of the TA-enantiomers were studied using a randomized, open two-way crossover design with administrations of oral and intravenous single doses of 200 mg rac-TA. GET in healthy subjects was 134.7±21.6 min, the normal range was calculated from 88.3 to 181.1 min. The mean GET in all IDDM patients was significantly prolonged (178.2±28.1 min; P <0.001). Only 50% of the patients ( n =11) were found to have normal GET (group A), the other half of the population ( n =11) were considered to have delayed GET (group B). Mean GET values were 156.9±21.5 in group A ( P =0.028) and 199.4±13.9 min in group B, respectively, suggesting that gastric motility is significantly different from non-diabetic controls even in patients with apparently normal gastric emptying. Times to peak plasma concentrations ( t max ) of both TA-enantiomers were similar in both groups and thus, unrelated to measures of gastric emptying. In contrast, maximum concentrations ( C max ) and area-under-the-curve values (AUC) of both enantiomers were reduced by about 30% in patients with delayed GET. Although these differences resulted in statistical significance for the AUC of both enantiomers ( P <0.05), linear regression analysis showed only modest correlation between GET and the extent of TA-enantiomer absorption ( r 2 =0.31 and 0.22 for R (+)-/ S (−)-TA, respectively). The study suggests that prolonged gastric emptying is frequently present in IDDM. Delayed gastric emptying, however, does not substantially affect the rate and extent of absorption of both TA-enantiomers.