Transcript Introduction to Pharmacology

Introduction to Pharmacology
Ed Bilsky, Ph.D.
Department of Pharmacology
University of New England
What is Pharmacology?
• Pharmacology is the study of what drugs do and
how they do it
– toxicology is a related field that deals with the
undesirable effects of chemicals on living systems,
from the cellular level up to whole ecosystems
• A knowledge of pharmacology is essential for
using drugs safely and effectively in therapy
• Pharmacology has had, and continues to have, an
enormous impact on society
Study: Old drugs might give TB a 1-2 punch
Feb 26, 2009
By LAURAN NEERGAARD
WASHINGTON (AP) - Scientists might have found a way to deal drug-resistant tuberculosis a one-two
punch using two old, safe antibiotics - and studies in ill patients could begin later this year.
TB is one of the world's oldest killers, and the lung disease still claims the lives of more than 1.5 million
people globally every year. The bacteria that cause TB are fast becoming impervious to many
treatments, drug resistance that is seen worldwide but is a particular problem in parts of Asia and Africa.
While typically the TB doesn't respond to two top treatments, an emerging threat is so-called extensively
drug-resistant disease, or XDR-TB, that is virtually untreatable by remaining options.
So researchers are frantically hunting new approaches, including taking a fresh look at some old drugs.
The combo: Clavulanate to drop TB's shield, plus a long-sold injected antibiotic - meropenem, part of
that penicillin-style family - that then attacks the bacteria.
What happens in a lab doesn't necessarily work in people. Still, the findings were so compelling that two
teams of U.S. researchers - from the National Institutes of Health and New York's Montefiore Medical
Center - already are planning small patient studies in South Korea and South Africa. They hope to begin
those studies later this year.
Definitions
• Pharmacodynamics is the study of the effects of the
drug on the organism
– Molecular mechanisms --> clinical response
– Includes therapeutic and toxic side-effects
• Pharmacokinetics relates drug dosing to drug
concentration at the site of action and elsewhere
– Described as “what the body does to the drug”
– Includes the processes of absorption, distribution, metabolism
and elimination
• Pharmacogenomics is the study of genetic differences in
individuals and how it impacts drug therapy
– influences both pharmacokinetics and pharmacodynamics
What is a Drug?
• Any chemical compound that may be used on or
administered to humans or animals as an aid in
the diagnosis, treatment or prevention of
disease or other abnormal condition, for the
relief of pain or suffering, or to control or
improve any physiological or pathological
condition
• Any substance that brings about a change in
biological function through its chemical actions
Drug Nomenclature
Chemical name:
alpha-methylphenethylamine
Generic name:
dextroamphetamine
Trade name:
Dexedrine
Street name:
dexies, speed
H
H 2N
CH 3
Drug Nomenclature
• Generic names may have common roots and
endings that provide clues to their use and
actions
– diazepam, midazolam, lorazepam, alprazolam, etc.
– lidocaine, benzocaine, bupivacaine, procaine, etc.
• Copyrighted brand names are chosen to be
catchy, pleasing and easy to remember
– Valium, Lomotil, Propulsid
– naming does not follow a consistent pattern
We will typically use the generic name
Drug Classification
• Pharmacotherapeutic actions
– analgesics
• Pharmacological actions
– opioid analgesics
• Molecular actions
– mu opioid receptor agonists
• Other factors (source, chemical structure)
– opium alkaloids, phenylpiperidines (meperidine)
Additional Classifications
Inhibitors:
– used to describe drugs that prevent or reduce
physiological, biochemical or pharmacological activity
Activators:
– have actions opposite to those of inhibitors
Terms can be confusing and imprecise
History of Pharmacology
• Drug preparations have been used for thousands
of years to treat disease
• Most drugs in antiquity came from plant or animal
sources
– a significant number of modern drugs have also been
isolated from plants
• As our knowledge of physiology, molecular biology
and chemistry has increased, so has our
understanding of how drugs produce their
effects
Developments in Pharmacology
• Botany
– plants as a source of drugs
• Chemistry
– isolation and purification of compounds
– synthesis of new compounds
• Physiology/Pathology/Molecular Biology
– understanding how the body works in health and disease
• Pharmacology
– synthesis of the above fields --> mechanisms of drug action
Rational Drug Design
Modern Revolutions in Pharmacology
• Antibiotics
• Immunizations
• Psychotherapeutic Drugs
• Oral contraceptives
• Receptor theory and molecular biology
• Pharmacogenomics
Pharmacotherapy
• The goal of pharmacotherapy is to be able to
produce the intended beneficial effect while
minimizing adverse/toxic effects
• A central hypothesis of pharmacotherapy is that
there is a relationship between the dose of the
drug given and the given effects that are
produced
– more specifically, it is the concentration of drug at
the site of action that in part determines the
measured effect
Pharmacotherapy
• Understanding the relationship between dose,
drug concentration, and effects helps the
clinician determine the appropriate drug therapy
for the individual patient
–
–
–
–
physiology
pathology
genetics
drug-drug interactions
Principles of Drug Action
1. Drugs do not create functions. Rather, they
modify existing functions in the body
2. Drug action is determined by how and where a
drug interacts with the body
3. No drug has a single action
Principle 1
• Drugs act by altering normal physiological or
abnormal pathological processes
• Drugs do not create a new function in a tissue or
organ
Digitalis:
– used to strengthen the action of the heart
– increases the influx of calcium ions into cardiac cells
– increases the force of contraction and cardiac output
Does not create a new way for the heart to contract
Principle 2
Site of action:
• A basic assumption of pharmacotherapy is that
there is a relationship between the concentration
of the drug at the site of action and the effects
that it produces
– The dosing regimen must result in a high enough
concentration of the drug at the site of action (and
maintain that concentration for some critical period of
time) for the intervention to be successful
• Clinical examples:
– CNS infections
– Tumors
Principle 2
Mechanisms of drug action:
1. Chemically alter body fluids
– antacids, osmotics
2. Alter cell membranes
– general anesthetics, alcohol (in part)
3. Act through specific receptors
–
–
–
–
majority of drugs fall into this category
tremendous diversity of receptors
distribution/localization of receptors
ability to fine tune the drug molecules to alter the
cellular response
Principle 3
• Every drug has multiple actions
– therapeutic window helps determine the usefulness of the drug
– benefit of the intended drug action
– risk associated with adverse effects