General principles of Pharmacology Flashcards
General principles of pharmacology are:
(1) The factors that affect the actions of drugs.
(2) Factors that affect drug reactions.
(3) Various types of drug interactions.
(4) Factors influencing drug response interactions.
Pharmacokinetic: Activities of the drug after it enters the body. Pharmacokinetics is the study of drug absorption, distribution, metabolism, and excretion.
A fundamental concept in pharmacokinetics is drug clearance, that is, elimination of drugs from the body.
Absorption: The transfer of the drug from the body fluids to the tissues.
(1) Active absorption: Carrier molecule such as a protein or enzyme actively moves the drug across the membrane.
2) Passive absorption: Diffuse across a membrane from area of higher concentration to an area of lower concentration (Water Soluble Drugs).
(3) Pinocytosis: Cells engulf the drug particle across the cell membrane.
Think packman!
(4) Bioavailability is a subcategory of absorption. It is the percentage of the administered drug dose that reaches the systemic circulation.
For drugs taken orally bioavailability occurs only after the medication has been absorbed and metabolized by the liver.
Oral drugs that have a first pass hepatic metabolism may only have a bioavailability of 20-40% as opposed to I.V medications that have a 100% bioavailability.
Factors that alter Bioavailability are:
(1) The drug from (e,g tablet, capsule, sustained release, liquid, trans-dermal patch, inhalation).
(2) Route of administration.
(3) Changes in Liver metabolism caused by dysfunction.
(4) GI mucosa and motility.
(5) Food and drugs.
(6) Solubility: Drugs that are fat soluble are absorbed faster than water-soluble drugs.
Distribution: Movement of drug throughout the body typically on proteins (albumin).
(1) Therapeutic effect: Drug levels in blood to produce desired effect. (a) Too high = toxic
(b) Too low = decreased effect
Metabolism: Chemical reaction by with liver converts drug to inactive compound.
(1) Metabolism occurs in the Liver, Kidneys, lungs, plasma, and intestinal mucosa.
(2) A patient with liver disease may require a lower dose of a medication that is metabolized by the liver or a different medication that is not metabolized by the liver.
Excretion: Elimination of drugs from the body.
(1) Kidney excretes the inactive compounds from the body in the urine.
Half - Life: Time required for the body to eliminate 50% of the drug.
(1) Kidney, Liver disease and old age can increase the half-life increasing risk of toxicity.
Pharmacodynamics: Drug’s actions and effects within the body.
(1) Primary or desired effect.
(2) Secondary effects (side effects) – desired or undesired.
Physical dependence:
A compulsive need to use a substance repeatedly to avoid mild to severe withdrawal symptoms.
Psychological dependence:
A compulsion to use a substance to obtain a pleasurable experience.
Pharmacogenetic disorder:
A genetically determined abnormal response to normal doses of a drug.
Receptor:
A specialized macromolecule that binds to the drug molecule, altering the function of the cell and producing the therapeutic response.
Alterations in Cellular Environment:
A drug that alters cellular function can increase or decrease the physiologic functions of the cell Ex: Increased heart rate, decrease blood pressure.
Therapeutic Response:
Alteration of cell to achieve the desired response.
Agonist:
Drug that binds with a receptor to produce the therapeutic response.
Antagonist:
Drug binds to receptor stronger than the agonist thus producing no pharmacologic effect Ex: Narcan is antagonist to morphine.
Adverse reaction:
Undesirable drug effects.
Allergic reaction:
A drug reaction that occurs because the individual’s immune system views the drug as a foreign substance.
Drug idiosyncrasy:
Any unusual or abnormal reaction to a drug that a patient can have, that do not occur in the vast majority of patients taking the same drug.
Drug tolerance:
A decreased response to a drug, requiring an increase in dosage to achieve the desired effect.
Cumulative drug effect:
A drug effect that occurs when the body has not fully metabolized a dose of a drug before the next dose is given.
Toxic: A harmful drug effect if it is delivered in high dose or when blood concentration levels exceed therapeutic level (as seen in patients with Liver or Kidney disease).
(1) May be reversible or irreversible depending on organ/tissue damage. Liver has ability to regenerate but hearing loss may be irreversible due to streptomycin toxic reaction.
(2) You have to know the signs and symptoms of toxicity for drugs you are giving.
Pharmacogenetics Reactions:
Inherited traits that cause abnormal metabolism of the drug
Pharmaceutic phase:
The dissolution of a drug. Usually applying to the breakdown of tablets.
Drug Interactions:
When one drug interacts with or interferes with the action of another drug.
Additive drug reaction:
A reaction that occurs when the combined effect of two drugs is equal to the sum of each drug given alone.
Synergism:
A drug interaction that occurs when drugs produce an effect that is greater than the sum of their separate actions.
Antagonist Drug Reaction:
When one drug interferes with the action of another, causing neutralization or a decrease in the effect of one drug.
Drug - Food Interactions:
Drug given orally, food may impair or enhance its absorption.
Age:
immature or aging organ function affects metabolism of a drug.
Weight:
Average weight is approximately 150 lb for both men and women. A medication may need to be increased or decreased.
Gender:
Women require smaller dose due to differences in body fat and water ratio compared to men.
Disease:
Liver disease may affect ability to metabolize or detoxify a drug.
Route of Administration:
IV drug produce the most rapid response than any other method.
Drug Use and Pregnancy:
(1) Teratogen: A substance that may produce physical or functional defects in a human embryo or fetus.
(2) Federal Drug Administration established five categories:
(a) Pregnancy CAT: A, B, C, D, X
