Phamacological Principles - Pharmacodynamics Flashcards
Pharmacodynamics
The relationship between drug concentrations and the pharmacological response. Its purpose is to invoke a positive change in a lack of appropriate physiological function for therapeutic effects. It increases/decreases rate of function, or modifies strength of function
Its pathways is receptor interactions, enzyme interactions, and/or nonselective interactions
Receptor Interactions
A receptor is a reactive site on the surface or inside of a cell. The molecular structure of the drug is important
5 drug types for receptor interactions
- Agonist - drug binds to the receptor; there is a response
- Partial agonist (agonist-antagonist) - drug binds to the receptor; the response is diminished compared with the response elicited by an agonist
- Antagonist - drug binds to the receptor; there is no response. Drug prevents binding of agonists
- Competitive antagonist - drug competes with the agonist for binding to the receptor. If it binds, there is no response
- Noncompetitive antagonist - drug combines with different parts of the receptor and inactivates it; agonist then has no effect
Enzyme Interactions
Enzymes are substances in our cells that activate almost all chemical reactions in our cells. Inhibition of enzyme activity is more common than enhancement of enzyme activity
Nonselective interactions
No interactions with receptors or enzymes, but they act on cell membranes or cellular processes
6 types of therapy in pharmacotherapeutics
- Acute therapy - to sustain life or treat a disease in acutely or critically ill patients (ex. pressors)
- Maintenance therapy - prevents the progression of a disease or a condition (ex. antihypertensives)
- Supplemental therapy - supplementing the body with what it needs, but it cannot make its own (ex. insulin)
- Palliative care - comfort care. To make the patient as comfortable as possible
- Supportive therapy - Maintains the integrity of body functions when a patient is recovering from illness or trauma (ex. fluids when patient is having vomiting or diarrhea)
- Prophylactic therapy - to prevent illness or undesirable outcomes (ex. COVID vaccines)
Therapeutic index
Ratio of drug’s toxic level to the level that provides therapeutic benefits. It determines drug safety
Low TI means that the difference between a therapeutic active dose and a toxic dose is small. There is a greater likelihood of causing an adverse reaction; requires close monitoring
Define tolerance and dependence
Tolerance - a decreasing response to repeated drug doses
Physical dependence - the physiological need for a drug to avoid physical withdrawal symptoms (ex. tachycardia in a patient dependent on opioids)
Physiological dependence - the obsessive desire for the effects of a drug
Effects of drug interactions
It describes the alteration of the action of one drug by another, which can happen with food as well. It can inc/dec the actions of one or both involved drugs. Either beneficial or harmful
Can occur anytime during ADME
Additive effects of drug interactions
The combined effects of the drugs combine such that if two drugs of similar action are administered at the same time, the action of one plus the action of the other results in the total effect of both drugs being given. (1 + 1 = 2)
Synergistic effects of drug interactions
When the action of one drug enhances the action of another.The two drugs administered together interact in such a way that their combined effects are greater than the sum of the effects for each drug given alone. (1 + 1 = >2)
Antagonistic effects of drug interactions
When the combination of two drugs results in drug effects that are less than the sum of the effects for each drug given separately. (1 + 1 = <2)
Incompatibility
When giving parenteral drugs.When two parenteral drugs are mixed together, and the result is a chemical deterioration of one or both of the drugs.
Adverse Drug Event (ADE)
Any undesirable occurrence involving medications. It may be due to external errors made by providers or malfunctioning equipment, or internal errors such as medications not taken as prescribed. Can be preventable or non-preventable
2 types of ADE
- Medication error (ME) - a preventable situation in which there is a compromise in theTen Rights of medication use: Right patient, right drug, right time, right route, right dose, right documentation, right reason, right patient education, right to refuse, and right assessment or evaluation
- Adverse Drug Reaction (ADR) - Any reaction to a drug that is unexpected and undesirable and occurs at the therapeutic dosages
