Intro to Pharmacology (9/23b) [Biomedical Sciences 1] Flashcards
3 types of drug nomenclature
Chemical (EX: n-acetyl-p-aminophenol)
Generic (EX: acetaminophen)
Trade names (EX: Tylenol, Panadol)
3 roles of FDA
Approval
Regulation
Classification
FDA - Approval
Based on safety and efficacy of the drug
FDA - Regulation
Drugs go through multiphase processes (animals→ human trials) that takes 10-15 years
FDA - Classification
Prescription (Rx) versus over the counter (OTC)
At least initially, usually only approved for Rx
After many years of post-marketing surveillance to make sure no immense side effects, they may decide to reclassify to allow OTC
Do PTs prescribe drugs?
No
Except military Its may prescribe analgesics and anti-inflammatories
Important to make pt aware of drug interactions
Pharmacodynamics - Overview
Site of action Mechanism of action Receptor site Dose-Response curve Potency Drug safety Therapeutic index Drug selectivity
Pharmacodynamics - Site of Action
Location where a drug exerts its effect
Pharmacodynamics - Mechanism of Action
How a drug produces its effects
Pharmacodynamics - Receptor Site
Site on a cell where a drug exerts its effects
Pharmacodynamics - Dose Response Curve
Response of a drug proportional to dose
Pharmacodynamics - Drug Safety
median effective and toxic doses
Therapeutic Index
In many other countries, drug approval may depend on just being safe, not necessarily effective → may take longer for it to be available in the US
Pharmacodynamics - Therapeutic Index
Therapeutic Index (TI) = (Median toxic dose TD50 ) / (Median beneficial dose ED50 )
They consider the dose for 50 people to have toxic effects divided by dose for 50 people to have beneficial effects
The greater the ratio number, the greater the TI, and generally the safer the drug
Pharmacodynamics - Drug Selectivity
If a drug is 100% selective, it only reacts with a specific type of receptor or cell in a specific time of tissue (unrealistic)
If a drug is not selective, it will interact with a receptor or cell in any tissue in the body
Range of non selectivity gives you your side effects
Pharmacodynamics - Dose
exact amount of a drug administered in order to produce a specific effect
Pharmacodynamics - Potency
measure of strength, or concentration, of a drug required to produce a specific effect
Doesn’t tell us anything about safety though → more potent doesn’t always
mean it is safe
Pharmacokinetics - Overview
How the body processes drugs
2 Routes of administration
3 main phases
Pharmacokinetics - Routes of Administration
Enteral
Parenteral
Pharmacokinetics - Enteral Administration
involves GI tract, experiences first pass effect
Less bioavailable, more distributed
Oral - taken and swallowed
Buccal - tucked into cheek pocket
Sublingual - stuck under the tongue
Rectal - inserted into rectum (even if pt unconscious)
First pass effect
part of a drug is metabolized before it reaches the target tissue
not all of it will be available later for an effect
happens with anything that is administered enterally
Pharmacokinetics - Parenteral Administration
Inhalation, intranasal, injection (IV, IM, or intrathecal, epidural), topical, transdermal
Requires some vehicle to administer
No first pass effect, but that also means risk of overdose
More bioavailable, less distributed
Topical and transdermal utilized by PTs - spreading across the skin (EX: iontophoresis, spreading with ultrasound)
Pharmacokinetics - 3 Main Phases
Absorption
Distribution
Elimination
Pharmacokinetics - Absorption
movement across membrane depends on membrane structure and function
Passive diffusion
Active transport
Other mechanisms (EX: Facilitated diffusion, Endocytosis and exocytosis)
Pharmacokinetics - Passive diffusion (absorption)
most drugs are lipid soluble and dissolved right into the membrane
Pharmacokinetics - Active transport (absorption)
Requires energy but can work against a gradient
Pharmacokinetics - Factors Affecting Absorption and Distribution
Route of administration
Properties of the drug
Endogenous carriers
Endogenous barriers
Storage and redistribution
Pharmacokinetics - Administration Routes (distribution)
Enteral routes - less bioavailable, more distributed
Parenteral routes - more bioavailable, less distributed
Pharmacokinetics - Properties of the drug (distribution)
Lipid solubles will be able to get into the cell via passive diffusion
Active transport requires energy but can work against a gradient
Pharmacokinetics - Endogenous carriers (distribution)
Endogenous - native to the body (EX: endorphins are one of the body’s biggest natural painkillers)
Protein channels or pores required by drug to help transport across membrane
Pharmacokinetics - Endogenous barriers (distribution)
Prevents drug from entering certain areas
EX: blood brain barrier
Pharmacokinetics - Storage and redistribution (distribution)
common for some portion of a drug to be stored before it is eliminated
Storage sites: adipose (most common), bone marrow, muscle, liver and kidney
Adverse consequences – can build up to toxic levels (ex: anaesthetics)
Pharmacokinetics - Elimination
Metabolism
Excretion
Drug Elimination Rates
Pharmacokinetics - Metabolism (elimination)
Biotransformation - breaking lipid soluble drugs into water soluble chunks to be able to be excreted
Happens mostly in the liver
Pharmacokinetics - Excretion (elimination)
Renal - primary site of excretion are kidneys (urination)
Respiratory - taking deep breaths
Less commonly - GI, sweat, saliva, lactation
Pharmacokinetics - Drug elimination rates (elimination)
Based on clearance and half life
Clearance
ability of the body to get rid of the drug
Based on the rate of blood flow, efficiency of liver and kidneys
Half life
how long it takes to get 50% of remaining drug out of the body
Important to know to prevent overdose
Dosing schedule
based on avg of when most of the drug should be eliminated from the body
Considers what plasma concentration is ideal for it to have its effect
Dosing windows or “therapeutic windows”
Newer Techniques for Drug Delivery
Controlled release preparations
Implanted drug delivery system
Targeting specific cells/tissues
Controlled release preparations (new technique)
EX: Coated pills, extended time release capsules → liver breaks down coating, more drug available to release over time
Implanted drug delivery system (new technique)
EX: patches that insert to surgical site, release slowly over specified amount of time
Targeting specific cells/tissues (new technique)
Manufacturing drugs to specifically bind to a certain receptor
Factors Affecting Pharmacokinetics
Genetics
Disease (esp. liver/kidneys)
Drug interaction (slow, speed, nullify)
Age (old→organs less efficient, young→organs less developed)
Diet (can inhibit metabolic enzymes)
Sex (women more vulnerable due to fluctuating hormones)
Pathology, alcohol, smoking, etc
