Different Gastric Emptying Time

Some studies have shown that women demonstrate greater duration in the gastric residence time of medications, which is reflected in an increased lag time of absorption, compared to men. This effect is increased when medication is taken with food, even when adjusted for the timing of the menstrual cycle (Majaverian et al, 1987). This was consistent with other reports that men had faster emptying times for both liquid and digestible solids than women (Majaverian et al, 1988; Wright et al, 1983). The length of time and variability of gastric emptying in women was also reported by Notivol et al (1984) to be altered in relation to the menstrual cycle and was shortest at mid-cycle (MacDonald 1965; Booth et al 1957).

These changes can affect the amount of drug in the blood. Miaskiewicz et al (1982) showed that, after a single dose of sodium salicylate, absorption was slower and achieved a lower level in women. This has also been shown for ibuprofen. The Tmax was observed to be more than 54min in females, compared to a Tmax of 31.5 min in males. Majaverian even showed a delay of 9.5 h before absorption occurred in one woman (Majaverian et al, 1987). Sex differences in plasma salicylate albumin binding capacity have been reported (Miaskiewicz et al, 1982) and, for other agents (Allen and Green-blatt, 1981), ^-globulin transport systems have been reported to be altered with the menstrual cycle.

Some effects on absorption can be subtle, such as the greater absorption of alcohol in women due to their reduced gastric mucosal and liver alcohol dehydrogenase activity compared to men. This results in higher circulating levels of alcohol, in spite of body weight corrections (Frezza et al, 1990), with obvious implications. Odansetron, on the other hand, is more slowly metabolized by women and thus may be more effective.

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