How Medications Get Absorbed By Your Body
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
💊 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
💡Oral Administration
💡First Pass Effect
💡Intestinal Wall
💡Bioavailability
💡Intravenous Injection
💡Intramuscular Injection
💡Subcutaneous Injection
💡Sustained Release Formulas
💡Rate of Dissolution
💡Lipid Solubility
💡pH Partitioning
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.
Transcripts
medication absorption is the movement of
a drug from its side of administration
into the blood
oral drugs enter the stomach where they
either dissolve
and pass through the cell membranes of
epithelial cells lining the stomach
or travel undissolved through the
stomach to the small intestine which is
the most common side of absorption
here drugs dissolve
and pass through the intestinal wall
oral drugs then travel through the
portal venous system to the liver where
they undergo the first pass effect
during this process the liver
metabolizes some of the drug either
inactivating it
or excreting it into bile for
elimination from the body
the remaining amount of active drug
leaves the liver and reaches General
circulation and Target organs
if a drug is administered via
intravenous injection it passes directly
into the bloodstream thus bypassing
absorption in the GI tract
if administered through intramuscular or
subcutaneous injection the drug enters
either muscle or subcutaneous tissue
where it passes through gaps between
cells into capillary walls and then into
General circulation or Target organs
also bypassing absorption in the GI
tract
bioavailability is the net amount of a
dose of a drug that is actually absorbed
into the bloodstream
the bioavailability of oral drugs is
less than 100 percent because of the
first pass effect of the liver
in contrast the bioavailability of IV
drugs is 100 percent because they are
not exposed to the first pass effect of
the liver
different drug formulations alter
bioavailability because they are not
absorbed at the same rate or to the same
extent
for example tablets dissolve at varying
rates
in terracotted drugs dissolve in the
small intestine not the stomach because
gastric emptying time differs between
individuals absorption times also vary
sustain release formulas contain tiny
spheres that dissolve at different rates
resulting in a steady drug release
throughout the day but also resulting in
variable absorption
some factors affecting drug absorption
are the rate of dissolution drugs that
dissolve faster are absorbed faster
surface area since the lining of the
small intestine has more surface area
than the lining of the stomach most
drugs are absorbed faster in the small
intestine
blood flow the greater the concentration
gradient between the drug-filled stomach
and the rapidly flowing drug-free blood
the faster the absorption
lipid solubility highly lipid soluble
drugs pass through the phospholipids in
the cell membrane more easily than drugs
of low lipid solubility
and pH partitioning absorption is faster
when the difference between the pH at
the site of administration and the pH of
the plasma attracts more drug molecules
to ionize in the plasma
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