Comment
Author: Admin | 2025-04-28
Accepted value of 3 h and is independent of the physical characteristics of the dosage forms, such as density and size, as well as of food (Dressman and Reppas, 2016). However, the gastric transit time is known to vary and so does the drug bioavailability. This variability might eventually lead to unpredictable levels of drug plasma and can severely limit the clinical efficacy. Gastrointestinal movements are of two types: propulsive and mixing; they are mainly affected by the fed or fasted state as well as the sleep cycle. The peristalsis motilities primarily determine the passage rate and thus, the residence time of a drug after oral administration (Rouge et al., 1996). In humans, the intestinal content has been shown to pass through the intestinal tract at a rate of 3 cm/min (Said and Mohammed, 2006). The passage rate is higher in the upper parts of the intestinal tract and declines toward the ileum. A drug capsule requires 3–4 h to pass through the entire small intestine. However, the transit time is considerably greater in the large intestine and depends on the volume of fiber in the intake. In healthy humans, the route time through the large intestine is estimated to be around 2 to 4 days (Read et al., 1980). The residence time in the intestine also imitates the absorption of drugs that are poorly soluble or that dissolve slowly in the intestinal fluids, as well as of the pharmaceutical formulations that sustain the release of the drug. Furthermore, the transit or residence time is essential for small drug molecules that are absorbed by transport carriers, as these drugs are favorably absorbed in the location with the highest carrier density (Dressman and Reppas, 2016). For instance, vitamin B2 is absorbed mostly in the proximal small intestine via sodium-dependent, carrier-mediated transport (Said and Mohammed, 2006). Hence, influences that effect intestinal motility can impact the bioavailability of vitamin B2. Thus, the extent of drug absorption after oral administration is directly affected by the GI residence time (Sakr, 1999).Food can influence the absorption of drugs: it can decrease, increase, delay, or accelerate drug absorption (Custodio et al., 2008). Food affects the GI functions such as gastric emptying, intestinal transit time, bile acid secretion, stomach pH change, and liver blood flow increase. Further, it can alter the physiochemical characteristics of drugs, such as solubility, intestinal permeability, size, and dissolution profile. In general, hydrophobic drugs
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