Phamacodynamics Flashcards
what is pharmacodynamics
study of the biochemical and physiological effects of drugs and their mechanisms of action, including the relationship between the dose (or concentration) of a drug and the effect it produces
the effects of most drugs results from what
their reversible association with a functional macromolecular component of the cell
what is a receptor or “drug target”
a functional macromolecular component
the receptor is a component of what
a cell or organisms that interacts with a drug and initiates the chain of biochemical or physiological events lead to the effects of the drug
what are the general types of drug receptors for endogenous physiological regulatory molecules
- neurotransmitters
- hormones & growth factors
- autocoids (substances which are formed and act locally)
other cellular proteins or constituents of drug receptors
- enzymes
- transport proteins; carrier molecules
- ion channnels
- structural proteins
- nucleic acids; nuclear transcription factors/elements
define agonists
drugs that mimic the effects of endogenous ligands by interaction with the same receptor
define antagoinists
compounds that inhibit the response of a specific agonist by competition for binding sites
how are drug receptors identified or classified
on the basis of the relative potencies of structurally related agonists and the effect or lack thereof, of selective antagonists or agonists
what are the major signalling mechanisms
- intracellular response elements; transcription factors; DNA-coupled receptors
- transmembrane enzymes, including tyrosine protein kinases
- ligand gated ion channels (iontropic)
- G protein coupled receptors (metabotropic)
see diagrams: slide 6-9
see diagrams: slide 6-9
name a few drug actions not mediated by receptors
- chelating agents
- antacids
- chemical neutralization
- osmotic diuretics
what are chelating agents
drugs used to treat pts whose body is heavily burdened or has high levels of toxic metals; chelating agents bind heavy metals, take them to the kidney and excrete them; only interacting with heavy metal, not other body tissue
what are antacids
neutralize stomach acid, don’t interact with receptor
what are chemical neutralization
treat certain toxicities. Ex. Heprain a coagulant is a heavily charged polysaccharide. If too much heparin is in the body the pt will start to bleed. The anecdote for heparin is to squirt in protame which is heavily positively charged
what are osmotic diuretics
manatal, works as an osmotic particle exerting coagulative propeties, gets filtered in the glomerulus, doesn’t get reabsorbed and then draws water in with it bc of its osmotic properties and increases urine formation; not interacting with receptors
see diagrams: slide 12-13
see diagrams: slide 12-13
what is the spare-receptor concept
-a maximal effect can be produced by a drug when only a small proportion of receptor is occupied; the response is not linearly proportional
see diagrams: slide 15+16
see diagrams: slide 15+16
efficacy
- the maximum effect of a drug is termed efficacy
- this term does not refer to the therapeutic efficacy of the drug, but to the stimulus properties of the drug receptor complex
potency
- is a comparative measure that refers to the different doses of two drugs that are needed to produce the same effect
(Full) Agonist
-is a drug capable of generating a maximal response
Partial Agoinst
- is a drug that will generate a response, but that response is less than the maximum
antagonist
- is a drug that reduces the effect of an agonist (an agonist must be present?)
inverse agonist
- is a drug that stabilizes an “active receptor” in the inactive conformation
see diagrams: slide 18-21
see diagrams: slide 18-21
what are they types of drug antagonism
- competitive
- noncompetitive
- physiologic (functional)
- Chemical (neutralization)
see diagrams: pic 23-26
see diagrams: pic 23-26
what pharmacodynamic changes occur with aging
- CNS more “sensitive”
- Beta adrenoceptors “less sensitive”
- orthostatic hypotension is more common
- potassium, electrolyte imbalance is more common
- the incidence of occult blood loss with aspirin or NSAIDs is higher
what is heterogeneity in the elderly
aging associated with physiologic decline and an increase in the prevalence of disease
how is heterogeneity in the elderly slowed
by maintaing physical fitness
what clinically impacts heterogeneity in the elderly
- increased biologic variation is characteristic of this age group
- physiologic functions that affect drug disposition
- each pt must be evaluated individually
geriatric prescribing
-Adequate review of patient medication regimens; obtain a detailed drug history
-Critically address whether drug therapy is indicated at all; reevaluate drug use at frequent intervals
-Consider physiologic or pathologic changes that may affect drug response
-Pick endpoints to follow carefully
Start low and go slow
-Communicate effectively; enhance patient compliance; emphasize the alliance with the patient
