7-27 General Principles of Pharmacology Flashcards
Definition of pharmacology?
Pharmacology - the study of the actions, effects, and disposition (or fate) of drugs in the body. Other related disciples include toxicology
Definition of drug?
Drug = any chemical. Limiting this definition is seldom useful. Medically, any agent used in the treatment or prevention of disease, or prevention of pregnancy.
Definition of pharmacodynamics?
Pharmacodynamics - the study of drug effects and their mechanisms of action. (The study of what drugs do to you).
Definition of pharmacokinetics?
Pharmacokinetics - quantitative descriptions of the time course of drug and metabolite concentrations in plasma, tissue and urine: i.e., drug fate (the study of what your body does to drugs).
Definition of pharmacotherapeutics?
Pharmacotherapeutics (Clinical Pharmacology) - The application of drugs in the prevention, treatment or diagnosis of disease and their use in purposeful alteration of normal functions
Definition of drug action?
Drug Action: Drugs cause changes at the molecular level by interacting with biological macromolecules, i.e., they have a molecular mechanism of action.
Action = biochemical event.
Example: a certain drug blocks a Na+/K+ - ATPase on the cell membrane which ultimately leads to a change in Ca++ flux.
Definition of drug effect?
Drug Effect: Most often, the clinical practitioner is more concerned with the effect of a drug on the body, i.e., a change in a physiological function.
Effect = physiological event.
Example: a certain drug increases the contractility of the heart. Often, we can describe the effects (both bad and good) of a drug in detail, but have incomplete information to describe its molecular mechanism of action.
What is a therapeutic window?
a “window” or range of plasma drug concentration, not too little and not too much drug, to obtain optimal therapeutic effects
What is the MEC?
Minimum Effective Concentration
In plasma or other tissue, fluid, or compartment
What does the dose have to do with the effectiveness of a drug? In a basic sense, how does changing the dose change the effect of the drug?
Dose: The actions and effects of drugs are dose-dependent.
- There is some dose below which no effect is observed
- There is some dose above which no greater effect is observed
- There is a dose‑response relationship
- There is a threshold concentration of drug or minimum effective concentration (MEC) in the plasma or other tissue fluid or compartment.
There is a maximum tolerated concentration of drug above which toxicity occurs.
What must a physician do in order to achieve the therapeutic window for a drug? What 4 factors will make this up?
A key goal of therapy is to choose the right drug for each individual patient, and to administer the drug in the correct quantity (dose) over the correct dosing interval. To achieve this goal the clinician must understand the factors that determine:
Absorption of the drug.
Distribution of the drug throughout the tissues.
Elimination of the drug from the body.
Drug action and effect.
Why are onset and termination important events in a graph of a therapeutic window?
Indicate start and end point of desired therapeutic range
Major objective of drug therapy is to keep plasma conc. above this range
What limits percutaneous administration of drugs?
keratinous nature of skin severely limits absorption
What is transdermal/percutaneous delivery good for treating?
- Used to treat dermatological conditions or to deliver slow, sustained systemic absorption.
- Transdermal patches or via creams and ointments (percutaneous) - some drugs delivered through skin patches, e.g., nicotine for smoking cessation, scopolamine for motion sickness, nitroglycerin for angina.
How would you describe percutaneous absorption of drugs? What kinds of drugs do well with this delivery system? What other local routes are similar?
1.Absorption is slow and sustained.
Lipid soluble drugs, e.g., steroids, penetrate skin much more readily than water soluble drugs.
2.Other local routes would include eyedrops, nasal sprays, etc.
How many enteral routes are there? What are they? What does enteral mean?
. Enteral - means via the gastrointestinal tract.
- Sublingual (SL)
- Oral (per os or PO)
- Rectal (rect)
How would you describe the absorption rate of SL administration? Why?
· Warm moist environment for rapid drug dissolution
· Rich blood flow, close to mucosal surface
· More rapid absorption than oral
What are the advantages of SL administration? Disadvantages?
· The unpleasant taste of most drugs limits usefulness of sublingual approach.
· Drug absorbed from sublingual sites is not carried directly to the liver and thus no “first pass” metabolism occurs. Compare this to oral administration.
