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Drug Absorption: Factors Affecting GI Absorption

Drug Absorption: Factors Affecting GI Absorption

The process of oral drug absorption can be influenced by several factors. Weakly acidic drugs tend to be absorbed more readily from the stomach due to their nonionized state. However, absorption may be less efficient in the upper intestine, where drugs are often ionized. Interestingly, despite the stomach's apparent advantage for drug absorption, its mucous layer can hinder diffusion. Its surface area is also smaller than the intestine's, which can further slow down the absorption rate.
In...

Protein Absorption

Protein Absorption

Proteins in the gastrointestinal tract typically come from food, but they can also originate from disintegrated cells or secreted enzymes. In the stomach, the enzyme pepsin breaks down these proteins into polypeptides. The fragments then move into the duodenum as a semi-fluid mass called chyme. Pancreatic proteases, such as trypsin and chymotrypsin, and intestinal brush border enzymes like carboxypeptidases further dismantle the polypeptides into tripeptides, dipeptides, and free amino acids.

Factors Influencing Drug Absorption: Anatomical Parameters

Factors Influencing Drug Absorption: Anatomical Parameters

Drug absorption involves the movement of drugs from the point of administration into the systemic circulation. Initially, Gastrointestinal (GI) motility propels the drug through the digestive tract and into the stomach. However, the stomach's high acidity and limited surface area restrict its role in drug absorption for most drugs. The drug then moves from the stomach to the small intestine via gastric emptying, which can be slowed by various factors, including interactions with other...

Methods for Studying Drug Absorption: In vitro

Methods for Studying Drug Absorption: In vitro

In vitro experiments are crucial for understanding the transport and absorption of drugs through biological materials. These studies employ varied methods such as the diffusion cell method, the everted sac technique, and the everted ring technique.
The diffusion cell method uses a two-compartment cell, including a donor compartment with the drug solution, which simulates the environment where the drug is applied, and a receptor compartment with a buffer solution, which simulates the environment...

Methods for Studying Drug Absorption: In situ

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In situ experiments, such as the Doluisio method and Single-Pass Perfusion technique, provide critical insights into drug uptake by simulating in vivo conditions for drug absorption.
The Doluisio method involves perfusing a prepared segment of a rat's small intestine with a solution of radiolabeled drug and a non-absorbable marker. This helps to differentiate between absorbed and non-absorbed drug concentrations. The intestinal segment is connected at both ends using tubing and syringes,...

Inorganic Nitrogen Assimilation

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Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...

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Accurate and Simple Measurement of the Pro-inflammatory Cytokine IL-1β using a Whole Blood Stimulation Assay

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Observations upon ammonia absorption from the human ileum.

J D Swales, M Papadimitriou, O M Wrong

|September 1, 1973

Summary

Ammonia and hydrazine absorption in the human ileum increased with higher pH solutions. Non-ionic diffusion is a key factor in ammonia absorption from the ileum.

Area of Science:

Gastroenterology
Physiology
Pharmacokinetics

Background:

The human ileum plays a crucial role in nutrient and drug absorption.
Understanding the absorption mechanisms of specific compounds like ammonia and hydrazine is important for physiological and clinical contexts.

Purpose of the Study:

To investigate the absorption of ammonia and hydrazine from the human ileum.
To determine the influence of solution pH on the absorption rates of ammonia and hydrazine.

Main Methods:

Experiments were conducted using a human ileal sac model with an exteriorized stoma.
Solutions containing ammonia and hydrazine at varying pH levels were instilled into the ileal sac.

Main Results:

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Absorption of both ammonia and hydrazine was significantly greater from solutions with a higher pH.

This suggests a pH-dependent absorption mechanism.

Conclusions:

Non-ionic diffusion is a critical mechanism driving ammonia absorption in the human ileum.
The findings have implications for understanding the behavior of ammonia and related compounds in the gastrointestinal tract.