Pharmacology: Oral Meds Absorption

Summary

This video explains the process of drug absorption in the gastrointestinal tract. It covers how drugs enter the stomach, dissolve, and are absorbed, highlighting the difference between acidic and alkaline drugs. Acidic drugs are absorbed in the stomach, while alkaline drugs move into the small intestine. The script also addresses how drugs are metabolized in the liver through first-pass metabolism and enterohepatic cycling. Additionally, it discusses how some drugs are excreted, and the factors that can prevent full absorption, such as binding to intestinal contents or bacterial breakdown in the intestines.

Takeaways

• 😀 Absorption refers to the transport of drugs across the mucosal membranes in the gastrointestinal tract.
• 😀 Drugs enter the gastrointestinal tract through the mouth and travel down the esophagus to the stomach.
• 😀 Once in the stomach, drugs dissolve and acidic drugs are absorbed due to the acidic environment of the stomach.
• 😀 Alkaline drugs are not absorbed in the acidic stomach, instead passing into the small intestine for absorption.
• 😀 After absorption, drugs enter the bloodstream and travel through the liver via the portal system.
• 😀 Some drugs are metabolized in the liver immediately, a process known as first-pass metabolism.
• 😀 Other drugs may be secreted back into the small intestine via the bile in a process called enterohepatic cycling.
• 😀 A portion of the oral dosage may also be absorbed in the large intestine or excreted in feces.
• 😀 Not all of the drug dosage is absorbed; some may bind to intestinal contents and be prevented from crossing mucosal membranes.
• 😀 Some drug molecules are broken down by bacteria in the ileum and colon, preventing absorption.

Q & A

What is drug absorption in the context of the gastrointestinal tract?

Drug absorption refers to the process by which drugs pass through the membranes of mucosal cells in the gastrointestinal (GI) tract, allowing the drug to enter the bloodstream.

How does a drug enter the gastrointestinal tract after ingestion?

After ingestion, the drug travels through the esophagus into the stomach, where it dissolves and begins the absorption process.

What happens to acidic drugs in the stomach?

Acidic drugs are typically absorbed in the stomach because the acidic environment helps keep the drug in an uncharged form, which makes it easier for the drug to pass through cell membranes.

How do alkaline drugs differ from acidic drugs in terms of absorption?

Alkaline drugs are less likely to be absorbed in the acidic stomach, so they pass through the pyloric sphincter into the small intestine, where they are absorbed more effectively.

What role does the small intestine play in drug absorption?

The small intestine plays a major role in the absorption of alkaline drugs, as its environment is more conducive to the absorption of these drugs compared to the stomach.

What is first pass metabolism?

First pass metabolism refers to the initial metabolism of a drug in the liver after it is absorbed into the bloodstream. This process can reduce the drug’s effectiveness before it reaches systemic circulation.

What happens to some drugs after they pass through the liver?

Some drugs are secreted back into the small intestine in the bile, a process known as enterohepatic cycling, where they can be reabsorbed and continue to circulate in the body.

Can all of a drug dosage be absorbed in the gastrointestinal tract?

No, not all of the drug dosage is absorbed. Some drug molecules may bind to intestinal contents or be broken down by bacteria in the ileum and colon, preventing their absorption.

What factors might prevent a drug from being absorbed in the GI tract?

Factors such as binding of the drug to intestinal contents, breakdown by gut bacteria, or the drug’s chemical properties (e.g., being poorly soluble or unstable) can prevent absorption.

What is enterohepatic cycling and how does it affect drug absorption?

Enterohepatic cycling is the process in which drugs, after being metabolized by the liver and excreted into the bile, are reabsorbed back into the bloodstream from the small intestine. This can prolong the presence of the drug in the body.