The effect of food on oral absorption is complex and sometimes difficult to predict. The following are a listing of some mechanisms by which food alters oral absorption:
• Food can delay gastric emptying which can result in delayed absorption.
• Food can initially raise the pH of stomach followed by a lowering of pH caused by a subsequent increase in acid secretion. This fluctuation in pH can impact the oral absorption of drugs with pH-dependent solubility profiles.
• Food can cause alterations in blood flow (i.e., splanchnic blood flow).
• Food can cause an increase in bile secretion which can help enhance the solubility of lipophilic compounds.
• Food components can chemically or physically interact with drug substance.
Food effects are greatest when the drug is administered shortly after a meal. High calorie and high fat meals are the most likely to cause a food effect.
Pentagastrin pretreated dogs have been used to assess food effects on oral absorption. Dogs exhibit a high variability in their stomach pH. Pentagastrin treatment helps to lower basal stomach pH in dogs and in addition reduces variability in stomach pH. Lentz et al. (2007) validated this model using a set of nine compounds with known propensities for human food effect.
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