How Medications Get Absorbed By Your Body

Nucleus Medical Media

22 Jun 202304:19

Summary

TLDRThe script discusses the process of medication absorption, highlighting that oral drugs are absorbed primarily in the small intestine, undergoing the first-pass effect in the liver, which can reduce bioavailability. Intravenous and other non-oral routes bypass this effect, ensuring full bioavailability. Factors influencing absorption include dissolution rate, surface area, blood flow, lipid solubility, and pH differences, with formulations like sustained-release impacting the rate and extent of absorption.

Takeaways

💊 Medication absorption involves the movement of a drug from its administration site into the bloodstream.
🧬 Oral drugs may dissolve in the stomach or pass undissolved to the small intestine, the primary site for absorption.
🛡️ Drugs that pass through the small intestine enter the liver through the portal venous system, where they undergo the first-pass effect.
🔄 The first-pass effect in the liver can metabolize some of the drug, reducing its active amount in the bloodstream.
💉 Intravenous (IV) drugs bypass the GI tract and liver, entering directly into the bloodstream with 100% bioavailability.
🦵 Drugs administered via intramuscular or subcutaneous injection enter muscle or tissue and reach the bloodstream without GI absorption.
📉 Bioavailability of oral drugs is less than 100% due to the first-pass effect in the liver.
🕒 Different drug formulations affect bioavailability, as they are absorbed at different rates and extents.
🏃 The rate of drug absorption is influenced by factors like dissolution rate, surface area, blood flow, lipid solubility, and pH partitioning.
🌡️ Highly lipid-soluble drugs are absorbed more easily, and absorption is faster when the pH difference between the administration site and plasma favors ionization in the plasma.

Q & A

What is medication absorption?
-Medication absorption is the process by which a drug moves from its site of administration into the bloodstream.
How do oral drugs typically enter the body?
-Oral drugs enter the body through the stomach, where they either dissolve and pass through the cell membranes of epithelial cells or travel undissolved to the small intestine for absorption.
Why is the small intestine the most common site for drug absorption?
-The small intestine is the most common site for drug absorption because it is where most drugs dissolve and pass through the intestinal wall due to its large surface area and rich blood supply.
What is the first pass effect and how does it affect oral drugs?
-The first pass effect is the process where the liver metabolizes some of the drug after it enters the bloodstream from the gastrointestinal tract, either inactivating it or excreting it into bile. This reduces the bioavailability of oral drugs.
How does intravenous injection bypass the first pass effect?
-Intravenous injection bypasses the first pass effect because the drug is directly introduced into the bloodstream, avoiding the liver and gastrointestinal tract.
What are the two other common methods of drug administration that bypass the gastrointestinal tract absorption?
-Intramuscular and subcutaneous injections are two other common methods that bypass gastrointestinal tract absorption, as the drug enters muscle or subcutaneous tissue and then into general circulation.
What is bioavailability and why is it important?
-Bioavailability is the net amount of a drug dose that is actually absorbed into the bloodstream. It is important because it determines the effectiveness and potency of the drug in the body.
Why is the bioavailability of oral drugs less than 100 percent?
-The bioavailability of oral drugs is less than 100 percent due to the first pass effect of the liver, which can inactivate or excrete a portion of the drug before it reaches general circulation.
How do different drug formulations affect bioavailability?
-Different drug formulations affect bioavailability because they may not be absorbed at the same rate or to the same extent due to varying dissolution rates and other factors.
What are some factors that can affect the rate of drug absorption?
-Factors affecting drug absorption include the rate of dissolution, surface area, blood flow, lipid solubility, and pH partitioning.
How do sustained-release formulas impact drug absorption?
-Sustained-release formulas contain tiny spheres that dissolve at different rates, resulting in a steady drug release throughout the day but also leading to variable absorption.

Outlines

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💊 Medication Absorption and Bioavailability

This paragraph delves into the process of medication absorption, explaining how oral drugs dissolve in the stomach or small intestine before passing through epithelial cells into the bloodstream. It highlights the first pass effect in the liver, which metabolizes drugs, potentially inactivating or excreting them before they reach general circulation. The paragraph also contrasts oral administration with intravenous, intramuscular, and subcutaneous injections, which bypass gastrointestinal absorption. Bioavailability is introduced as the net amount of drug absorbed into the bloodstream, with oral drugs typically having less than 100% bioavailability due to liver metabolism, while IV drugs have 100%. The influence of drug formulation on bioavailability is also discussed, including the variability introduced by different release rates and dissolution patterns in sustained-release formulas. Factors affecting drug absorption, such as dissolution rate, surface area, blood flow, lipid solubility, and pH partitioning, are outlined, emphasizing their impact on the speed and efficiency of drug absorption.

Mindmap

Keywords

💡Medication Absorption

Medication absorption refers to the process by which a drug moves from its site of administration into the bloodstream. This is a fundamental concept in the video, as it explains how different routes of administration can affect the drug's bioavailability. For example, oral drugs must dissolve and pass through the gastrointestinal tract before entering the blood, while intravenous injection bypasses this process, leading to different absorption rates and bioavailability.

💡Oral Administration

Oral administration is a common method of drug delivery where the medication is taken by mouth. The script mentions that oral drugs enter the stomach and either dissolve or travel undissolved to the small intestine, which is the primary site for absorption. This method is significant as it introduces the concept of the first-pass effect, which impacts the drug's bioavailability.

💡First Pass Effect

The first pass effect is a phenomenon where a drug is metabolized by the liver before it enters the general circulation. The video script explains that after oral drugs pass through the gastrointestinal tract, they undergo this effect, which can inactivate or excrete part of the drug, thus affecting the amount of active drug reaching the general circulation.

💡Intestinal Wall

The intestinal wall is the barrier that drugs must pass through after dissolving in the small intestine. The script describes how drugs pass through the cell membranes of the epithelial cells lining the intestine, which is a critical step in the absorption process. The surface area of the small intestine contributes to the efficiency of drug absorption, as highlighted in the transcript.

💡Bioavailability

Bioavailability is the net amount of a drug that is absorbed into the bloodstream and is a key measure of drug effectiveness. The video script explains that oral drugs have bioavailability less than 100 percent due to the first pass effect, while IV drugs have 100 percent bioavailability because they bypass the liver's first pass effect. This term is central to understanding the efficiency of different drug administration routes.

💡Intravenous Injection

Intravenous injection is a method of drug administration where the drug is injected directly into the bloodstream. The script notes that this bypasses absorption in the gastrointestinal tract, leading to 100 percent bioavailability. This method ensures that the full dose of the drug is immediately available to the body, which is crucial for emergency situations or when rapid drug action is needed.

💡Intramuscular Injection

Intramuscular injection is another route of drug administration where the drug is injected into muscle tissue. The script explains that the drug then passes through gaps between cells into capillary walls and enters general circulation. This method, like subcutaneous injection, bypasses the gastrointestinal tract and is an alternative to IV administration for certain drugs.

💡Subcutaneous Injection

Subcutaneous injection involves injecting the drug into the subcutaneous tissue, just beneath the skin. The video script describes how the drug enters this tissue and then passes into general circulation, similar to intramuscular injection. This method is used when a slower, more sustained release of the drug is desired.

💡Sustained Release Formulas

Sustained release formulas are drug formulations designed to release the medication at a steady rate over time. The script mentions that these formulas contain tiny spheres that dissolve at different rates, resulting in a steady drug release throughout the day. This is an important concept for medications that need to maintain a consistent therapeutic level in the body.

💡Rate of Dissolution

The rate of dissolution refers to how quickly a drug dissolves in the body. The video script explains that drugs that dissolve faster are absorbed more quickly, which is an important factor in drug absorption. This concept is relevant when comparing different drug formulations and their absorption profiles.

💡Lipid Solubility

Lipid solubility is a measure of a drug's ability to dissolve in fats, oils, or lipids. The script states that highly lipid-soluble drugs pass through the cell membrane more easily than those with low lipid solubility. This property is crucial for understanding how a drug's chemical structure can affect its absorption and transport across biological barriers.

💡pH Partitioning

pH partitioning is the process by which the difference in pH between the site of administration and the plasma affects drug absorption. The video script explains that absorption is faster when there is a greater pH difference, attracting more drug molecules to ionize in the plasma. This concept is important for understanding how environmental factors can influence the efficiency of drug absorption.

Highlights

Medication absorption is the movement of a drug from its site of administration into the blood.

Oral drugs either dissolve in the stomach and pass through epithelial cell membranes or travel to the small intestine, the most common site of absorption.

In the small intestine, drugs dissolve and pass through the intestinal wall.

Oral drugs travel through the portal venous system to the liver, undergoing the first pass effect where the liver metabolizes some of the drug.

The first pass effect can inactivate some of the drug or excrete it into bile for elimination.

The remaining active drug leaves the liver and reaches general circulation and target organs.

Intravenous (IV) administration bypasses absorption in the gastrointestinal (GI) tract, directly entering the bloodstream.

Intramuscular or subcutaneous injections allow drugs to pass through gaps between cells into capillaries and then into general circulation, also bypassing the GI tract.

Bioavailability is the net amount of a drug dose absorbed into the bloodstream.

Oral drugs have less than 100% bioavailability due to the first pass effect of the liver.

IV drugs have 100% bioavailability as they are not exposed to the first pass effect.

Different drug formulations alter bioavailability due to varying absorption rates and extents.

Tablets dissolve at varying rates, and enteric-coated drugs dissolve in the small intestine, not the stomach.

Sustained-release formulas contain tiny spheres that dissolve at different rates, resulting in steady drug release and variable absorption.

Factors affecting drug absorption include the rate of dissolution, surface area, blood flow, lipid solubility, and pH partitioning.