Pharmacokinetics: a drug’s movement throughout the body (what the body does to drug) to its
site of action
➔ Four phases of pharmacokinetics
1. Absorption
a. Movement of a drug from its site of administration into the blood
b. Factors affecting absorption
i. Rate of dissolution
ii. Surface area (small intestine - larger surface)
iii. Blood flow
iv. Lipid solubility
v. pH partitioning (difference between pH level increases the absorption)
2. Distribution
a. Movement of the drug once absorbed, throughout the body to the sites of action
b. Determined by
i. Blood flow to tissues
ii. Exiting the vascular system
iii. Entry into cells
c. Blood-Brain Barrier (BBB)
i. CNS capillaries have thicker walls with tight junctions in between
ii. Drugs must be able to pass through cells of the capillary wall
iii. Only drugs that are lipid soluble or have a transport system can cross the
BBB to a significant degree
3. Metabolism
a. Aka biotransformation
b. Defined as the enzymatic alteration of drug structure
c. Takes place in liver
d. Therapeutic Consequences of Drug Metabolism
i. Accelerated renal drug excretion
ii. Drug inactivation
iii. Inc. therapeutic action
iv. Inc. or dec. toxicity
, e. Special Considerations
i. Age
ii. First-pass effect
iii. Nutritional status
iv. Competition between drugs
4. Excretion
a. Removal of drugs from the body; done by the kidneys
b. Can exit the body through urine, sweat, saliva, breast milk or expired air
● First-Pass Effect
○ When the liver breaks down a percentage of the orally administered drug resulting
in a reduced amount of the drug reaching systemic circulation; typical with oral
drugs
○ Alternate routes:
■ IV, rectal, SubQ, IM, inhaled, sublingual, buccal, intraocular, etc.
● Serum drug levels
● Half-life
● Albumin-bound drug vs unbound drug
● Enteric-coating of drug
● Sustained release preparations
Pharmacodynamics: How drugs affect the body
➔ Dose-response relationships
➔ Drug-receptor interactions
➔ Therapeutic index
➔ Abilities of Drugs
◆ Drugs can inhibit or enhance abilities in the body. It CANNOT create new
abilities
1. Receptor Drugs: Agonist vs Antagonist
a. Receptors
i. Special chemicals in the body that most drugs interact with to produce
effects
site of action
➔ Four phases of pharmacokinetics
1. Absorption
a. Movement of a drug from its site of administration into the blood
b. Factors affecting absorption
i. Rate of dissolution
ii. Surface area (small intestine - larger surface)
iii. Blood flow
iv. Lipid solubility
v. pH partitioning (difference between pH level increases the absorption)
2. Distribution
a. Movement of the drug once absorbed, throughout the body to the sites of action
b. Determined by
i. Blood flow to tissues
ii. Exiting the vascular system
iii. Entry into cells
c. Blood-Brain Barrier (BBB)
i. CNS capillaries have thicker walls with tight junctions in between
ii. Drugs must be able to pass through cells of the capillary wall
iii. Only drugs that are lipid soluble or have a transport system can cross the
BBB to a significant degree
3. Metabolism
a. Aka biotransformation
b. Defined as the enzymatic alteration of drug structure
c. Takes place in liver
d. Therapeutic Consequences of Drug Metabolism
i. Accelerated renal drug excretion
ii. Drug inactivation
iii. Inc. therapeutic action
iv. Inc. or dec. toxicity
, e. Special Considerations
i. Age
ii. First-pass effect
iii. Nutritional status
iv. Competition between drugs
4. Excretion
a. Removal of drugs from the body; done by the kidneys
b. Can exit the body through urine, sweat, saliva, breast milk or expired air
● First-Pass Effect
○ When the liver breaks down a percentage of the orally administered drug resulting
in a reduced amount of the drug reaching systemic circulation; typical with oral
drugs
○ Alternate routes:
■ IV, rectal, SubQ, IM, inhaled, sublingual, buccal, intraocular, etc.
● Serum drug levels
● Half-life
● Albumin-bound drug vs unbound drug
● Enteric-coating of drug
● Sustained release preparations
Pharmacodynamics: How drugs affect the body
➔ Dose-response relationships
➔ Drug-receptor interactions
➔ Therapeutic index
➔ Abilities of Drugs
◆ Drugs can inhibit or enhance abilities in the body. It CANNOT create new
abilities
1. Receptor Drugs: Agonist vs Antagonist
a. Receptors
i. Special chemicals in the body that most drugs interact with to produce
effects
