Download Chapter 19 The Body and Drugs

The Pharmacy Technician
FOUNDATIONS AND PRACTICES
Chapter 19
The Body and Drugs
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 19.1
Receptor site.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Mechanism of Action (cont.)
• 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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 19.3
Example of agonistic and antagonistic drug action.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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.)
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Figure 19.8
The path.
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Solubility (cont.)
• 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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Bioavailability
• The amount of drug that is available for
•
use
Determined by the body’s ability to absorb
the drug
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Bioavailability (cont.)
• 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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
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
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Identifying Drug-Abusing Patients
• Always bring possible drug abuse
situations to the attention of the
pharmacist!
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Table 19.1
Medications That May Cause Problems When Mixed with Alcohol
The Pharmacy Technician: Foundations and Practices
Mike Johnston, Karen Davis, and Jeff Gricar
Copyright ©2009 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.