1. PHARMACY TECHNICIAN
CHAPTER NINETEEN

2. Pharmacodynamics
The study of the biochemical and physiologic effects of drugs
The study of the mechanisms of action of drugs
The study of how drugs affect the body

3. Pharmacokinetics
The study of the time course of a drug and its metabolites in the body following drug administration
The study of how the body handles drugs
The study of how the body changes a drug from its original form into something that the body can use
The study of how the body secretes and eliminates metabolized drugs
The study of how the body affects drugs

4. Receptor site.

5. Receptors
Most drugs affect the body by interacting with specific drug receptors
This process is likened to a lock and key
Each cell in the body has receptors (“locks”) requiring a specific “key” to produce an effect
Specific drugs are developed to “unlock” certain receptors in the body, producing the desired effect

6. Mechanism of Action
Refers to how a drug works and produces its desirable (and sometimes undesirable) effects
Key factor is the drug’s ability to bind to receptor sites
Once a drug binds to a receptor site, it may stimulate or prevent cellular activity
Agonist—drug binds to receptor sites and causes some action to occur
Antagonist—drug binds to receptor sites and prevents other chemicals or drugs from affecting the cell

7. Example of agonistic and antagonistic drug action.

8. Drug Absorption
How a drug enters the body and eventually enters the bloodstream
Largely dependent upon the type of the drug and reason for use
Based on route of administration (oral, parenteral, etc.)

9. Drug Distribution
Once absorbed, drug is distributed throughout the body by circulatory system
Some of the drug binds to plasma proteins
Some of the drug “floats” through the bloodstream
“Floating” drug may interact with receptors, producing therapeutic effect

10. Drug Metabolization
Once distributed, drug is broken down or “metabolized” for use
Typically but not always metabolized in the liver
The body metabolizes or “digests” drugs into usable products that cause desired effects

11. Drug Excretion
After being metabolized and used, drug becomes a waste product
Must be cleared from the body
Ideally, drugs metabolize and are cleared at a steady rate
Steady metabolism and excretion ensure that the patient has a consistent amount of medication in the body

12. The path.

13. Solubility The ability of a material to dissolve in a given medium
Water-soluble drugs dissolve in the presence of water
Fat- (or lipid-) soluble drugs dissolve in the presence of fats (lipids)
Drug solubility affects the ability of the body to absorb the medication
Fat-soluble drugs are very quickly absorbed into the body
Water-soluble drugs are usually only partially soluble, preventing the product from being absorbed too rapidly

14. Bioavailability The amount of drug that is available for use
Determined by the body’s ability to absorb the drug
Several factors influence absorption:
Solubility of the medication
How the drug is manufactured
Presence of different buffers
Salt forms vs. nonsalt forms
Rate and volume of distribution
Clearance from the body

15. Addiction
Defined as both a psychological and a physiological dependency
Specific withdrawal symptoms must present following abrupt change in use
Some signs of addictive behavior include:
Absorbing focus on the substance
Increased tolerance
Painful withdrawal

16. Medications That May Cause Problems When Mixed with Alcohol