Download 9-12-04 Intro Terminol

Pharmacology Introduction
Terminology
• Drug
– Pure chemical compound with specific chemical
structure
• Biological effects
• Chemical effects
• Therapeutic Effect
– Intended effect of a drug
• Drug Indication
– Therapeutic use of a drug
• Contraindication
– Situation when a particular drug should NOT be used
Undesired Effects of Drugs
• Side Effects
– Nuisance more than dangerous
• E.g. dry mouth, sedation,
• Adverse Effects
– May be harmful
• E.g. darrhea, vomitting, CNS disturbances
• Toxic Effects
– Drug poisoning
• Most drugs exhibit all effects depending on
dose
Basic Concepts
• Site of Action
– Location within the body where the drug exerts
its therapeutic effect
• E.g. aspirin acts at the hypothalamus to reduce fever
• Mechanism of Action
– How a drug produces its effects
• Anesthetic produce loss of pain by interrupting
sensory nerve conduction
• Receptor Site
– Drug usually exerts action once binding to
specific cell in the body
• Often site of binding is a specific receptor
• Receptor site is usually synonymous with Site of
Action
• E.g. morphine binds to opiod receptors in the brain
to reduce pain
– Same receptors as endorphins in exercise or fight of flight
• Agonists and Antogonists
• Drugs that bind to specific receptors and
produce a drug action are termed Agonists
• Drugs that bind to specific receptors but do
not produce any drug action are termed
Antagonists
– Antagonists are used as blocking drugs
• Naloxone is an antogonist to morphine receptor
• Used for treatment in morphine overdose
Dose-Response Curve
• Dose is the exact amount of a drug that is
administered in order to produce and effect
– The graph of the response versus a given dose is the
dose-response curve
– The response is often proportional to the dose
• Not always
• May hit a ceiling above which no therapeutic effect is
observed, but adverse effects may be
• ED50
– Effective dose that elicits 50% of maximal response
– Measure of potency
Agonist Dose Response Curves
Full agonist
Partial agonist
Response
Dose
Relative Potency
hydromorphone
morphine
codeine
Analgesia
aspirin
Dose
Effectiveness, toxicity,
lethality
• ED50 - Median Effective Dose 50; the dose at
which 50 percent of the population or sample
manifests a given effect; used with quantal dr
curves
• TD50 - Median Toxic Dose 50 - dose at which 50
percent of the population manifests a given toxic
effect
• LD50 - Median Toxic Dose 50 - dose which kills
50 percent of the subjects
Quantification of drug safety
Therapeutic Index =
TD50 or LD50
ED50
Drug A
100
sleep
death
Percent
50
Responding
0
ED50
LD50
dose
Drug B
100
Percent
Responding
sleep
death
50
0
ED50
dose
LD50
Time-Response Curve
• Relationship of drug response and duration
of the action
Drug Safety
• All drugs will act as poisons if taken in
excess
• Therapeutic effect is distinguished from
toxic effect by dose
• Factors such as route of administration,
absorption, and drug metabolism will
influence amount of drug reaching site of
action
Nomenclature
• All drugs typically have three names
– Chemical
• Gives the chemical structure of the compound
– Generic
• Often abbreviated form of chemical name
– Trade
• Name given by manufacturer to drug
Drug Schedules
• Schedule 1
– High abuse potential- no accepted medical use
• E.g. heroin, not to be prescribed
• Schedule 2
– High abuse potential – accepted medical use
• E.g. morphine, cocaine, no refills without new prescription
• Schedule 3
– Moderate abuse potential – accepted medical use
• E.g. codeine plus another drug, can be refilled 5 x in 6 months
• Schedule 4
– Low abuse potential – accepted medical use
• E.g. valium, phenobarbital, can be refilled 5 x in 6 months
• Schedule 5
– Limited abuse potential – accepted medical use
No limitations on refill of prescription