Chapter 2: Basic concepts and processes Flashcards
Absorption
Process that occurs from the time a drug enters the body to the time it enters the bloodstream to be circulated
Agonist
Drug that produces effects similar to those produced by naturally occurring hormones, neurotransmitters and other substances
Antagonist
Drug that inhibits cell function by occupying receptor sites
Antidote
Substance that relieves, prevents, or counteracts the effect of a poison
Bioavailability
Portion of a drug dose that reaches the systemic circulation and is available to act on body cells
Biotransformation
When drugs are altered from their original form into a new form by the body; also referred to as metabolism
Distribution
Transport of molecules within the body; after a drug is injected or absorbed into the bloodstream, it is carried by the blood and tissue fluids to sites of action, metabolism and excretion
Enterohepatic recirculation
Drugs or metabolites that are excreted in bile reabsorbed from the small intestine, returned to the liver, metabolized, and eventually excreted in urine
Enzyme Induction
Production of larger amounts of drug-metabolizing enzymes by liver cells; process accelerates drug metabolism because larger amounts of enzymes = more binding sites = more drug to be metabolized during a given time.
Enzyme inhibition
Process in which a molecule binds to enzymes and inhibits their activity
Excretion
Elimination of a drug from the body (kidneys, bowel, lungs, skin)
First-Pass Effect
phenomenon in which a drug gets metabolized at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation
Hypersensitivity
Immune-mediated reaction to a a drug
Loading dose
Dose larger than the regular prescribed daily dose of a medication; used to attain a therapeutic blood level
Maintenance dose
Quantity of drug that is needed to keep blood levers and/or tissue levels at a constant/steady level
Nephrotoxicity
Toxic or damaging effect of a substance on the kidney
Pharmacodynamics
Drug actions on target cells (what the drug does to the body)
Pharmacokinetics
Drug movement through the body to reach sites of action, metabolism and excretion (what the body does to the drug)
Prodrugs
Initially inactive drugs that exert no pharmacologic effects until they are metabolized
Serum drug level
Laboratory measurement of the amount of a drug in the blood at a particular time
Serum half-life
Time required for the serum concentration of a drug to decrease by 50%; also called elimination half-life
Drug Transport Pathways
Lipid-soluble drugs: just pass through cellular membrane
Protein channels: only some drugs can use this because most drug molecules are too large. Small ions use this pathway but are regulated
Carrier proteins: transport molecules from one side of the cell to the other; selective proteins
Drug transport Mechanisms
Passive diffusion - higher concentration to lower concentration
Facilitated diffusion - similar to above except drug molecules combine with a carrier substance (enzyme/protein)
Active transport - drug molecules are moved form an area of lower concentration to one of higher concentration. Process requires a carrier and release of cellular energy
Cytochrome P-450 (CYP)
Enzymes in the liver that metabolize most drugs
*most drugs act by mechanism of combining with receptor sites on cells
Drugs that do NOT act on receptor sites include…
Antacids: which act to neutralize the acid in gastric parietal cells
Osmotic diuretics: which increase the osmolarity of plasma and pull water of of tissues into the bloodstream
Drugs similar to nutrients (purines/pyrimidines)
Metal chelating agents: combine with toxic metals to form a complex that can be more readily excreted
Variables that affect drug actions
Dosage
Route
Drug-diet interactions
Drug-drug interactions
Additive effects
Occur when two drugs with similar pharmacologic actions are taken (ethanol + sedative drugs increases sedative effects)
synergism
Occurs when two drugs with different sites or MOAs produce greater effects when taken together (acetaminophen [non-opioid analgesic] + codeine [opioid analgesic] increases analgesic effects)
Interference of drugs
Interference of one drug with the metabolism of a second drug may result in intensified effects of the second drug.
Displacement of drugs
When a drug with a strong attraction to protein-binding sites may displace a less tightly bound drug. This increases the effects of the displaced drug because the displaced drug is freed from its bound form and becomes pharmacologically active. (Aspirin displaces warfarin and increases the drugs anticoagulant effects.
Patient-Related Variables
Age
Body weight
Genetics
Ethnicity
Sex
