Chapter 2: Pharmacologic Principles Flashcards
Pharmacology
The study or science of drugs
Drug
Any chemical that affects the physiologic processes of a living organism
3 Areas of Pharmacology
- Pharmaceutics
- Pharmacokinetics
- Pharmacodynamics
Chemical Drug Name
Describes the drug’s chemical composition, molecular structure
Generic Drug Name
(Nonproprietary name)
One generic name for any particular drug regardless of where you go.
Why is it important to know the generic name of a drug?
Easy to pronounce than chemical name and we go by generic name for less confusion.
Trade Drug Name
Proprietary name. Multiple brand names. Ex) Motrin
Drug classification
Drugs grouped together based on their similar properties.
Pharmaceutics
The study of how various dosage forms influence the way in which the drug affects the body.
Pharmacokinetics (PK)
- Study of what the body does to the drug.
- What happens to a drug from the time it is put into the body until the drug leaves the body.
Pharmacokinetics involves 4 processes (A,D,M,E)
Absorption, Distribution, Metabolism, Excretion
Pharmacodynamics
The study of what the drug does to the body. Involves drug to receptor relationships.
Pharmacotherapeutics (aka therapeutics)
Focuses on the clinical use of drugs to prevent and treat diseases.
It defines the principles of drug actions.
Toxicology
Study of adverse effects of drugs and other chemicals on living systems
Pharmacognosy
Study of natural drug sources (plants, animals, minerals)
Pharmacoeconomics
Focuses on the economic aspects of drug therapy.
The concept of pharmacokinetics is
Drug “entering” and “leaving” the body.
Drugs enter the body through
Absorption and distribution
Drugs leave the body through
Metabolism and excretion
PK: Absorption
Movement of a drug from its site of administration into the bloodstream for distribution to the tissues
What happens to a drug before it enters the systemic circulation?
It must pass through the liver before it reaches system circulation.
First-pass effect, bioavailability
First-pass effect
Reduces the bioavailability of the drug to less than 100%.
Bioavailability
The extent of drug absorption.
What factors affect the rate of drug absorption?
-How the drug is administered or it’s ROUTE of administration affects the rate and extent of absorption of that drug
Three basic routes of administration:
- External (GI tract)
- Parenteral (outside of GI, eg. Injections)
- Topical
Enteral Absorption
- The drug is absorbed into the systemic circulation through the oral or gastric mucosa or the small intestine.
- Includes, oral, sublingual, buccal, rectal.
Sublingually administered drugs are
absorbed rapidly because the area under the tongue has a large blood supply. Bypass the liver and yet are systemically bio available.
Parenteral Absorption includes
Intravenous, intramuscular, subcutaneous, intradermal, intraarterial, intrathecal, intraarticular
Parenteral Absorption is the
Fastest route by which a drug can be absorbed, followed by enteral and topical routes.
Medications given by the Parenteral route have the advantage of
Bypassing the first-pass effect of the liver.
Intravenous
Fastest delivery of drug into the bloodstream/circulation.
Aren’t subjected to first-pass effect.
Topical Absorption
Skin (including transdermal patches), eyes, ears, nose, lungs (inhalation), rectum, vagina
PK: Distribution
- Once a drug enters the bloodstream (systemic circulation), it is distributed throughout the body.
- Other definitions: transport of a drug to its site of action. Dispersion of drug throughout the tissues.
Distribution depends on
- Blood supply
- Protein-binding
- Water-soluble vs. fat-soluble
- Blood-brain barrier
Areas of rapid distribution in the body
The heart, liver, kidneys, brain.
Areas of slow distribution
Muscle, skin, fat, bone
What drug molecules can freely distribute to extravascular tissue?
Only drug molecules that are not bound to plasma proteins.
If a drug is bound to plasma proteins,
The drug-protein complex is generally too large to pass through the walls of blood capillaries into tissues.
Water-soluble vs. fat-soluble drug distribution
Water-soluble: while have a smaller volume of distribution and high blood concentrations.
Fat-soluble: have a larger volume of distribution and low blood concentrations.
Blood-brain barriers affect on drug distribution
Has barriers that make it difficult for drugs to pass through
Metabolism is aka …
Biotransformation.
What is the next step after absorption and distribution?
Metabolism
The main organ for metabolism of drugs is
The liver.
Other metabolic tissues include..
Skeletal muscle, kidneys, lungs, plasma and intestinal mucosa.
PK: Excretion
The removal of drugs from the body.
What is the primary organ used for elimination?
The kidneys
What other organs play a role in the excretion of drugs?
The liver and the bowel.
Biliary excretion
Excretion of drugs by the intestines.
Drugs eliminated by this route are taken up by the liver, released into the bile and eliminated in the feces.
Enterohepatic recirculation
Once certain drugs are in the bile, they may be reabsorbed into the bloodstream, returned to the liver and again secreted into the bile.
What are the PK factors?
Half-life, onset (start of therapeutic effect), peak (time required for drug to reach is maximum therapeutic response), duration, drug level
Half-life
Time it takes for one half of the original amount of a drug to be removed from the body.
Most drugs are considered to be effectively removed after
About five half-lives (around 97%)
On-set
Time it takes for the drug to elicit a therapeutic response
Peak
Time it takes for a drug to reach its maximum therapeutic response
Duration
Time a drug concentration is sufficient to elicit a therapeutic response
Peak level
Highest blood level
Trough level
Lowest blood level
Why must you monitor peak levels?
Because if the peak blood level is too high, then drug toxicity may occur.
Why must you monitor blood trough level?
Because the drug may not be at therapeutic levels to produce a response.
Why are peak and trough levels measured?
To verify adequate drug exposure, maximize therapeutic effects and minimize drug toxicity.
Pharmacodynamics (PD): Mechanisms of Action
- Receptor interactions
- Enzyme interactions
- Nonselective interactions
PD: Receptor interactions
Drugs bind to and interacts with receptors causing a drug response.
Agonist and antagonist.
What is the action of the drug type, agonist?
Binds and activates receptor’s site, effects occur. Mimics the body’s natural hormone/chemical’s action, can also be enhanced effect.
What is the action performed by the drug type, antagonist?
Binds, does not activate blocking/prevent the natural hormone/chemical’s action.
Enzyme interactions
Drug chemically binds to an enzyme molecule in a way that alters (inhibits or enhances) the enzyme’s interaction with its normal target molecules in the body.
Nonselective interactions
Do not interact with receptors or enzymes. Main targets are cell membranes and various cellular processes.
Ex) Antibiotics target bacterial cell wall.
What are the types of therapies?
Acute therapy, maintenance therapy, supplemental/replacement therapy, palliative therapy, supportive therapy, prophylactic therapy, empiric therapy
Acute therapy
Involves more intensive drug treatment and is implemented in the acutely ill (those with rapid onset of illness) or the critically ill.
Maintenance therapy
Prevents progression of a disease or condition.
It is used for the treatment of chronic illnesses.
Supplemental Therapy
Supplies the body with a substance needed to maintain normal function. Ex) iron
Palliative therapy
Goal is to make the patient as comfortable as possible.
Focuses on providing patients with relief from symptoms, pain and stress of a serious illness.
Supportive Therapy
Maintains the integrity of body functions while the patient is recovering from illness or trauma.
Prophylactic therapy
Provided to prevent illness or other undesirable outcome during PLANNED events. Ex) preop mess
Empiric Therapy
Based on clinical probabilities.
Involves drug administration when a certain pathological condition has a high likelihood of occurrence based on the patient’s initial presenting symptoms.
Contraindications
Any characteristic of the patient, especially a disease state, that makes the use of a given medication dangerous for the patient.
IT IS IMPORTANT TO ASSESS FOR CONTRAINDICATIONS!
Monitoring
Is important! Evaluating the clinical response of the patient to the treatment.
One must be familiar with a drug’s:
- intended therapeutic action (beneficial)
- unintended but potential adverse effects (predictable, adverse drug reactions)
Therapeutic Index (TI) gonna be on test
Ratio between toxic and therapeutic concentrations of a drug (LD50 to ED50).
Expresses the margin of safety for a drug
A large TI is considered ________ while a low TI ________________.
A large TI is considered safe while a low TI causes adverse reactions (not safe).
Drug concentration
Drug levels to evaluate toxic effects, therapeutic response
Patient’s condition
Drug response depends on medical and psychological conditions
Tolerance
Decreasing response to repeated drug doses
Dependence
Physiologic or psychological need for a drug
Drug interaction
Additive effect, synergistic effect, or antagonistic effect.
May be beneficial or harmful.
Adverse Drug events
Any undesirable occurrence involving medications. Predictable and well known.
Adverse Drug Events include:
- Adverse drug reaction
- Medication error
- Allergic reaction
- Idiosyncratic reaction
Adverse drug reaction
Unexpected, undesirable and occurs at therapeutic drug dosages
Idiosyncratic reaction
Abnormal response to a normal drug dosage, genetically determined.
Ex) G6PD deficiency.
Rate of Drug Absorption of Various Oral Preparations: From fastest to slowest
- Oral disintegration, buccal tablets, and oral soluble wafers
- liquids, elixirs and syrups
- suspension solutions
- powders
- capsules
- tablets
- coated tablets
- enteric-coated tablets
If there are low albumin levels,
There is not enough albumin for a drug to bind to, therefore blood is free floating in the blood and can raise the risk for blood toxicity.
Drug-drug interaction
Occurs when the presence of one drug decreases the actions of another drug that is administered at the same time
High creatinine levels and B.U.N indicate
Problem with the kidneys.
Allergic reaction
An immunologic hypersensitivity reaction resulting from unusual sensitivity of a patient to a particular medication.
A type of adverse drug event.
psychological dependence
physiologic needs for a drug to avoid physical withdrawal symptoms. Addiction.
partial agonist
drugs that bind to and activate a receptor, but have only partial efficacy at the receptor relative to a full agonist
loading dose
a large initial dose of a substance or series of such doses given to rapidly achieve a therapeutic concentration in the body
maintenance dose
the amount of a medication administered to maintain a desired level of the medication in the blood.
pharmacologic reaction
an extension of a drug’s normal effects in the body.
