Pharmacodynamics Flashcards
Pharmacodynamics
Action of drug on body. Determined by the drug-receptor interactions
What initiates biochemical or molecular activity
The drug-receptor complex
Drug receptor complex
The free drug binds to a receptor (either on a cell or on a plasma protein, etc)
Receptor
Any molecule to which a drug can bind and produce a measurable response
Types of receptors
Proteins, enzymes, nucleic acids, etc
Types of receptors
- G-protein
- Ligand-gated ion channels
- Enzyme linked receptors (insulin)
- IC receptors
Ion channels
Transmembrane protein channels that regulate the flow of ions across the membrane.
What regulates ion channels
The binding of a ligand (in this case the drug)
Example of ion channel
Nicotinic receptor stimulated by each results in Na influx, which creates an action potential
Protein receptors (g-protein)
7 pass membrane protein, ligand binds to receptor, which causes a release of the IC gamma, alpha, beta proteins and initiates a cascade
second messengers
These are receptors that are located inside the cell and are activated from the cascade. Turned on by G protein
Enzyme-linked receptors
A protein that spans the membrane once and forms dimers or subunit complexes
What happens when a ligand binds to an enzyme-linked receptor
Activates OR inhibits the cytosolic enzyme activity
What are the most common enzyme-linked receptors
Those that have tyrosine kinase in their structure (ex: platelet derived growth factory
Intracellular receptor
Receptor is entirely inside the cell, the ligand must therefore diffuse into the cell
What type of molecule will interact with an IC receptor
something that is lipid soluble
Signal amplification
A receptors ability to amplify the signal duration and intensity once it binds with a ligand
What are the 2 features of signal transduction
- Ability to amplify small signals
2. Mechanisms to protect the cell from excessive stimulation
Examples of chemicals or molecules that induce signal amplification
- hormones
- neurotransmitters
- peptides
How does signal amplification occur
A single ligand-receptor complex can interact with many G proteins, which multiplies the original signal
Desensitization
Occurs when the repeated administration of a drug results in the receptor being desensitized to the action of the drug. Receptors are still present on the cell but are unresponsive to the drug
Tachyphylaxis
Repeated drug administration that results in a diminished effect of the drug
Down-regulation
Reducing the number of receptors available for ligand (drug) to bind to. Can happen if the receptor undergoes endocytosis and recycled
Prototype drug
The first form of the a drug that is used to create alternative forms. Also called lead agents
Pharmacologic classification
Classification of a drug is based on what the medication does in the body. (i.e. propranolol is a beta blocker)
Therapeutic classification
Classification groups meds by outcomes (i.e. grouping drugs as antihypertensive)
Mechanism of action
How the medication actually works in the body (at the cellular or organ level). What the drug will be doing in the body to achieve the therapeutic effect
Major adverse reactions
Any major side effect that has been reported with the medication
Clinically significant drug or diagnostic test interaction
Any drug to drug interaction or any way that the drug may interact with a given diagnostic test (i.e. contrast)
Contraindications
Any reason the drug should not be prescribed to a patient
Efficacy
The degree to which a drug is able to induce maximal effects
Issues with Renal and hepatic function in prescribing meds
- Dose may need to be reduced if pt has kidney failure or issues
- Dose reduction with liver enzyme problems
Which patient demographic are liver enzymes underdeveloped
Infants and elderly patients
Concomitant disease
Is a second illness occurring at the same time as a primary illness (i.e. pt with pneumonia complicated by a kidney infection)
Concurrent therapy
Administering medical treatments at the same time as other therapies.
Indications
A symptom or particular circumstance that indicates the necessity for medical treatment or intervention
Absolute contraindications
Means the the medication or treatment could cause a life threatening situation
Relative contraindications
Caution should be used when two drugs or procedures are used together (done if the benefit outweighs the risk)
Contraindication
Situation in which drug, procedure, surgery, etc should bot be used because it may be harmful
Agonist
An agent (ligand) that binds to a receptor and elicits a biological response (signals an IC response)
What does the magnitude of the drug effect depend on
Drug concentration at the receptor site
What determines drug concentration at receptor site
Pharmacokinetics:
- Dose of drug
- Rate of absorption
- Metabolism
- Elimination
Potency
The amount of drug necessary to produce an effect of a give magnitude
The more potent a drug
The less time it takes to produce desired effect
The less potent a drug
The more time it takes to produce desired effect
Partial agonist
Is a weak agonist or weak drug. It will still bind to a receptor but the IC response is much weaker than with a strong agonist
Antagonist
Is a drug/ligand that binds to the receptor site and blocks cellular reaction. This will block drugs from interacting with cells and decrease actions of drug
What is efficacy dependent upon
The # of drug-receptor complexes formed and the efficiency of the cellular response
Which drug is more potent: Small EC50 or large EC50
Small, because it requires less drug concentration to reach 50% of desired effect
Inverse agonist
A drug that binds to the same receptor as the agonist but induces the opposite effect of the agonist
Competitive antagonist
If the antagonist and the agonist bind to the same site on the receptor.
What happens in competitive antagonism
The competitive antagonist will prevent the agonist from binding to receptors
Irreversible antagonists
Binding that cannot be overcome by adding more agonist. Blocks the ability for agonist to bind
How are the effects of competitive antagonists overcome
By adding more agonist
What effect does irreversible antagonism have on curve
Downward shift of the maximum, and no shift of the curve on the dose axis
EC50
The amount of drug it takes to reach 50% of desired effect
Kd
Represents the receptor affinity and is the concentration in which half of the receptors are bound
What does a lower Kd mean in relation to potency
Means the drug will be more potent. If the Kd is low, then the concentration of the drug that binds 50% of the receptors, means that the time it takes to reach max effect is short = potent
Purposeful reaction
A reaction from a drug that was intended and/or expected and is beneficial
Beneficial reaction
A reaction from a drug that is considered positive
Inadvertent reaction
Opposite of purposeful. The reaction was NOT intended
Adverse reaction
Opposite of beneficial reaction. Drug that causes a negative outcome
Chemical name of the drug
Based on molecular structure
Generic name
These drugs are copies of the brand name drugs. Named by the United States Adopted names council
Proprietary name
The trade, brand name is owned and chosen by the firm that markets a specific product (zocor)
Bioequivalence
When 2 drugs have the same bioavailability (rate and extent of absorption are equal)
Therapeutic equivalence
When 2 drugs are bioequivalents AND they have the same clinical effect/safety profile
