Pharmacokinetics
the study of what happens to the drug(s) in the patients body after administered. Includes absorption,
distribution, metabolism and excretion.
(ADME)
Absorption, Distribution, Metabolism, Excretion
What does ADME influence?
-the drug levels -kinetics of drug exposure to tissue -Therefore the performance and pharmacological
activity of the drug
Absorption
the process by which a drug crosses various barriers to reach the bloodstream
Which route of administration is absorption not considered a factor?
Intravenous
Bioavailability
the degree to which a drug is absorbed and becomes available via the general circulation
The two main methods of absorption:
1. Passive Processes 2. Active Process
Passive Processes (3)
(All require no energy)1. Simple diffusion 2. Facilitated Diffusion: H2O soluble drugs through pores or
channels 3. Pinocytosis/Phagocytosis: cells engulfing particles or droplets (less common)
,Active Process
Active Transport: requires energy to move substances against the concentration gradient
Seven Factors that Affect Drug Absorption
1. Blood Supply 2. Route of Administration 3. Ionization 4. Size of Drug Molecule 5. Drug Solubility 6.
Formulation of the Drug 7. Concentration of the Drug
Factors Affecting the Absorption of Oral Drugs
1. GIT disease may reduce the number of viili or cause diarrhea 2. Gut fill and pyloric empting rate may
delay transit of drugs into the small intestine where most of the absorption occurs 3. Drugs may bind to
GIT contents which may delay or prevent absorption 4. Low gastric pH may destroy or inactivate some
drugs
What are the Four Problems Ruminants Can Have WIth the Oral Route?
1. Dilution of drugs in the large rumen 2. Basic pH of the rumen may trap acidic drugs 3. Microbial
activity in rumen can affect the stability of many drugs 4. Variability in the rate of passage for feed
through the rumen (amount and digestible level of feed are factors)
00:02
03:12
Factors Affecting the Absorption of Parenteral Drugs (2):
1. Blood Supply to Injection Site 2. Number of sites used
,Parenteral Drugs Must be Formulated to Be (4):
1. Pyrogen free 2. Sterile 3. Adjusted to body pH 4. Adjusted to body osmolality
Factors affecting the Absorption of Topical Drugs:
1. Slow absorption if on skin due to sebaceous secretions and keratinized epithelium (only lipid soluble
molecules pass thru) 2. Increased absorption if the skin is broken, has increased circulation, or if a drug
such as DMSO is first applied
Factors Affecting the Absorption of Inhaled Drugs:
Very rapid absorption due to the large surface area and excellent blood supply of the lungs
How is Absorption Affecting by Drug Solubility?
-Lipid soluble drugs cross cell membranes more readily than water soluble drugs
How does the Size of the Drug Affect Absorption?
the smaller the drug molecule, the easier it can be absorbed - Drugs with a large molecular weight must
gain access to circulation through the lymphatic system which slows absorption
How is Absorption Rate Affected by the Ionization State of the Drug?
-Non-ionized drugs diffuse through cell membranes easier than drugs that have a charge (if the charged
drug molecule is in a body compartment that has the same pH, then it will readily pass, if its in a body
compartment with the opposite pH, it is not absorbed well and may be trapped
, How is Absorption Affected by the Formulation of the Drug?
1. Drugs may be combined with carriers or 2. have protective coatings, both of which control the rate
that the preparation dissolves before being available for absorption
How is the Absorption Rate Affected by the Concentration of the Drug?
-the higher the drug concentration at a site, the faster the absorption
How is the Absorption Rate Affected by the Blood Supply to the Absorptive Site? How Can the Blood
Supply be Increased? Decreased?
-The greater the blood supply the faster the absorption -Can be affected by amount of movement to the
area, massage and heat to the area both of which would increase the blood supply or cooling and
elevation of area or poor general circulation due to shock or cardiac failure which would decrease the
blood supply
Drug Distribution
-The dispersion of drugs from their site of absorption to the site of their action -Only a small amount of
the drug will eventually reach it's target site of action due to several factors
Six Factors Which Affect the Distribution Rate of Drugs
1. Protein Binding 2. Storage in tissues 3. Concentration Gradient 4. Dilution in Luminal Fluids 5.
Specilized Barriers 6. Disease Processes
How does the Concentration Gradient Affect Drug Distribution Rate?
Drugs to move down the concentration gradient
the study of what happens to the drug(s) in the patients body after administered. Includes absorption,
distribution, metabolism and excretion.
(ADME)
Absorption, Distribution, Metabolism, Excretion
What does ADME influence?
-the drug levels -kinetics of drug exposure to tissue -Therefore the performance and pharmacological
activity of the drug
Absorption
the process by which a drug crosses various barriers to reach the bloodstream
Which route of administration is absorption not considered a factor?
Intravenous
Bioavailability
the degree to which a drug is absorbed and becomes available via the general circulation
The two main methods of absorption:
1. Passive Processes 2. Active Process
Passive Processes (3)
(All require no energy)1. Simple diffusion 2. Facilitated Diffusion: H2O soluble drugs through pores or
channels 3. Pinocytosis/Phagocytosis: cells engulfing particles or droplets (less common)
,Active Process
Active Transport: requires energy to move substances against the concentration gradient
Seven Factors that Affect Drug Absorption
1. Blood Supply 2. Route of Administration 3. Ionization 4. Size of Drug Molecule 5. Drug Solubility 6.
Formulation of the Drug 7. Concentration of the Drug
Factors Affecting the Absorption of Oral Drugs
1. GIT disease may reduce the number of viili or cause diarrhea 2. Gut fill and pyloric empting rate may
delay transit of drugs into the small intestine where most of the absorption occurs 3. Drugs may bind to
GIT contents which may delay or prevent absorption 4. Low gastric pH may destroy or inactivate some
drugs
What are the Four Problems Ruminants Can Have WIth the Oral Route?
1. Dilution of drugs in the large rumen 2. Basic pH of the rumen may trap acidic drugs 3. Microbial
activity in rumen can affect the stability of many drugs 4. Variability in the rate of passage for feed
through the rumen (amount and digestible level of feed are factors)
00:02
03:12
Factors Affecting the Absorption of Parenteral Drugs (2):
1. Blood Supply to Injection Site 2. Number of sites used
,Parenteral Drugs Must be Formulated to Be (4):
1. Pyrogen free 2. Sterile 3. Adjusted to body pH 4. Adjusted to body osmolality
Factors affecting the Absorption of Topical Drugs:
1. Slow absorption if on skin due to sebaceous secretions and keratinized epithelium (only lipid soluble
molecules pass thru) 2. Increased absorption if the skin is broken, has increased circulation, or if a drug
such as DMSO is first applied
Factors Affecting the Absorption of Inhaled Drugs:
Very rapid absorption due to the large surface area and excellent blood supply of the lungs
How is Absorption Affecting by Drug Solubility?
-Lipid soluble drugs cross cell membranes more readily than water soluble drugs
How does the Size of the Drug Affect Absorption?
the smaller the drug molecule, the easier it can be absorbed - Drugs with a large molecular weight must
gain access to circulation through the lymphatic system which slows absorption
How is Absorption Rate Affected by the Ionization State of the Drug?
-Non-ionized drugs diffuse through cell membranes easier than drugs that have a charge (if the charged
drug molecule is in a body compartment that has the same pH, then it will readily pass, if its in a body
compartment with the opposite pH, it is not absorbed well and may be trapped
, How is Absorption Affected by the Formulation of the Drug?
1. Drugs may be combined with carriers or 2. have protective coatings, both of which control the rate
that the preparation dissolves before being available for absorption
How is the Absorption Rate Affected by the Concentration of the Drug?
-the higher the drug concentration at a site, the faster the absorption
How is the Absorption Rate Affected by the Blood Supply to the Absorptive Site? How Can the Blood
Supply be Increased? Decreased?
-The greater the blood supply the faster the absorption -Can be affected by amount of movement to the
area, massage and heat to the area both of which would increase the blood supply or cooling and
elevation of area or poor general circulation due to shock or cardiac failure which would decrease the
blood supply
Drug Distribution
-The dispersion of drugs from their site of absorption to the site of their action -Only a small amount of
the drug will eventually reach it's target site of action due to several factors
Six Factors Which Affect the Distribution Rate of Drugs
1. Protein Binding 2. Storage in tissues 3. Concentration Gradient 4. Dilution in Luminal Fluids 5.
Specilized Barriers 6. Disease Processes
How does the Concentration Gradient Affect Drug Distribution Rate?
Drugs to move down the concentration gradient
