Gastrointestinal tract absorption window

In most cases, oral drug delivery is the cheapest and most convenient method of dosing. Unfortunately, it is difficult to achieve a precise control of the plasma-concentration-time profile by this route due to marked intra- and intersubject variation in gastrointestinal transit even under the rigidly controlled conditions of the clinical trial. Daily patterns of food intake, activity, and posture are large contributors to this variation. Drugs that are only absorbed from specific areas of the gastrointestinal tract, i.e., have a narrow window of absorption, will be most affected by alterations in transit. The major determinants of this variation will be the amount of food and drink consumed. 

Ionic polymers release drugs in certain region of the gastrointestinal tract that may limit the applicability for drugs with narrow window of absorption. 

For several reasons it may be helpful to investigate the extent of absorption by determining the window for absorption in the gastrointestinal (GI) tract, for example ... 

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