Module 1: Intro to Pharmacology Flashcards
Define pharmacology
The word pharmacology is derived from the Greek words pharmakon meaning remedy and logos meaning study.
- Generally, pharmacology is considered the study of drugs.
What 4 aspects does pharmacology include?
- How a drug is delivered (it’s route of administration).
- How a drug works (it’s mechanism of action).
- The therapeutic effect of drugs on patients.
- The adverse effects of drugs on patients.
How are drugs classified? (3)
- Give an example of each
- Drugs – Traditional drugs (i.e. chemical agents).
- Biologics – Ex. Antibodies, and hormones.
- Natural Health Products – Ex. Herbals, vitamins, minerals.
Before a drug reaches the market there is research to determine if it is (2):
1) Safe
2) Effective
Define drug
Typically, we think of a drug as a “pill” or “capsule”.
- Drugs are actually chemicals.
- Within every pill are many molecules of a chemical.
- It is the chemical that actually produces the pharmacological effect.
How does one name drugs? (3)
- Chemical Name
- Describes the chemical structure of the molecule
- Is used by chemists but not by many others. - Generic Name
- A unique name that identifies a drug.
- The generic name is the name most often used in Pharmacology.
- It is the name that should be used by health care professionals (although it often isn’t). - Trade name
- The name assigned by a drug company.
- It is usually easy to remember and marketable.
- The major problem with trade names is many companies may make the same drug, therefore it may have many different trade names.
- Ambiguous so use generic name.
Briefly describe drug development:
- Approval of marketed drugs in Canada takes ~15 years
- Drug development moves through several different levels
- Total cost of new drug can be as high as ~800 million
Describe (7) steps of approval of marketed drugs in Canada
1) Pre-clinical Testing
- Cultured cells, living tissue, experimental animals
- Evaluate biological effects, pharmacokinetics, and toxicity
2) Clinical Trial Application
- Submitted to Health Canada prior to human studies
3) Phase I: Clinical Trial
- 20-100 healthy volunteers
- Evaluation of pharmacokinetics and pharmacodynamics
4) Phase II: Clinical Trial
- 300-500 patients with target disorder
- Therapeutic effectiveness, side effects, dosing info
5) Phase III: Clinical Trial
- 500-5000 patients with target disorder
- Therapeutic effectiveness verified, long term side effects assessed
6) New Drug Submission (NDS) submitted to Health Canada
- Report = effectiveness/safety
- Pre-clinical and clinical study results
7) Phase IV: Clinical Trial
- Post-marketing surveillance
- Efficacy and safety of drug
What are the (3) methods to administering drugs into people? Explain each.
1) Enteral - “involves GI Tract”
- Oral
- Rectal
2) Parenteral - “does not involve GI tract”
- Intravenous
- Intramuscular
- Subcutaneous
3) Topical
- Creams
- Patches
Define pharmacokinetics:
It is what the body does to the drug:
- Absorption
- Distribution
- Metabolism
- Excretion
During oral administration of a drug, where does most of the absorption occur?
Small intestine
During oral administration of a drug, how does the drug travel to the liver?
Carried by the portal blood supply
During oral administration of a drug, where is the primary site of metabolism?
- What are the 2 “fates”, explain each, and how the drug is excreted?
Liver
1) Systemic Circulation
- Brain, heart, muscle, kidney (primary excretion via urine)
2) Bile Duct
- Back into the intestine
- Excretion via feces
During parenteral injection of a drug, where is the primary site of absorption?
Systemic circulation
What are two physiological barriers to drug transport?
1) Intestinal Villi
2) Tight junctions
What does a drug need to exert its effects (2) ? Why?
Physical and chemical properties
- To pass through barriers
What does the nucleus contain?
Genetic material
What does the smooth ER do?
Metabolizes drugs, carbohydrates, and steroids
What does the rough ER do?
Synthesizes proteins
What does the golgi apparatus do?
Processes and packages proteins and lipids.
What does the mitochondria do?
Produces ATP (cell’s source of energy).
What does the cell membrane do (2)?
1) Separates the intracellular and extracellular environments
2) Controls which drugs can enter
What is the cell membrane composed of?
Composed of phospholipids which have a polar (water soluble), phosphate containing head and two fatty acid (lipid soluble) tails.
Why is the cell membrane also called the lipid bilayer?
The cell membrane is often called a lipid bilayer because of the arrangement of the phospholipids.
Is the cell membrane fluid?
The cell membrane is “fluid” because the phospholipids are flexible allowing them to undulate back and forth.
What else is embedded in the phospholipid membrane?
The cell membrane also contains proteins embedded in the phospholipids.
How do drugs cross the cell membrane (3)?
- Direct penetration of the cell membrane.
- Through ion channels and pores.
- Specific transport proteins (drug transporter’s).
What type of cells can penetrate the cell membrane directly?
Lipid soluble cells (lipophilic)
What type of cells can pass through ion channels and pores?
Channels and pores are very small - Therefore, only very small compounds
What are the 2 types of drug transporters? What are they important for?
1) Uptake: Move drugs from the outside to inside of cell
- Mediating intestinal absorption, renal excretion, and reaching target sites of action inside cells
2) Efflux: Move drugs from inside cell to outside
- They are important for protecting cells and are present in the intestine, placenta, kidney and at the blood brain barrier.
What are the (6) different types of drug molecules
- Polar Molecules
- Ions
- Quaternary Ammonium Compounds
- Ionizable Molecules
- Lipophilic Molecules
What are (2) characteristics of polar molecules? Provide an example.
1) Water soluble
2) Uneven distribution of electrical charge = no net charge
Examples:
- H2O
- Glucose
- Kanamycin
What are (2) characteristics of ions? Provide an example.
1) Total number of electrons do not equal total number of protons = negative/positive charge
2) Due to charge, cannot directly pass through cell membrane (only small ions)
Examples:
- Na+
- K+
- CL-
- Li+
What are (3) characteristics of quaternary ammonium compounds?
1) Have at least 1 N atom
2) Positive charge at all times
3) Unable to cross membranes due to positive charge
What are (2) characteristics of ionizable molecules?
How do you determine whether a weak acid or a weak base carries a charge?
How do we know if it is ionized or unionized?
1) Exist in charged/uncharged forms
2) Weak acids or weak bases
Determination of whether a weak acid or a weak base carries a charge depends on the pH of the surrounding medium.
Ionized/Unionized - Depends on the medium
a) Weak acid + Acidic medium (i.e. stomach) = non-ionized
b) Weak acid + Alkaline medium (i.e. small intestine) = ionized
c) Weak base + Acidic Medium (i.e. stomach) = ionized
d) Weak base + alkaline medium (i.e. small intestine) = non-ionized
What is a characteristic of lipophilic molecules?
- Lipid soluble
What is the impact of pH on drug movement?
Only non-ionized drugs can directly penetrate the cell membrane.
Most drugs are weak bases, meaning they can cross the membranes easier if they are what type of medium?
Alkaline
The acidic drug is unionized and therefore can/cannot cross the cell membrane?
Can
The basic drug is ionized and therefor can/cannot cross the cell membrane?
Cannot
What is ion trapping?
Provide an example.
Ion trapping occurs when there is a difference in pH on different sides of a membrane
- Drugs accumulate on the side of the membrane where they are ionized.
Example:
- An acidic drug is placed into an acidic environment. - Since acidic drugs are unionized in acidic environments, the drug is able to cross the membrane.
- The other side of the membrane is basic, therefore when the drug crosses the membrane is becomes ionized
- Since ionized drugs are unable to cross cell membranes, the drug is now “trapped” on the basic side of the membrane.
How do molecules pass through capillaries?
Fenestrations
- Small holes within the endothelial cells of the capillary
Can hydrophilic drugs penetrate endothelial cell wall?
No but, they can pass through the fenestrations to leave the capillaries
How do lipophilic drugs pass through capillaries?
Either between fenestrations, tight junctions, or directly through plasma membrane
How do drugs enter the brain?
The brain has a blood brain barrier which has tight junctions and no fenestrations
- Drugs must be lipophilic or have specific proteins that carry them into the brain
