Module A Flashcards
Heparin is largely confined to the plasma compartment because of its __________
high molecular weight
Maintenance doses are designed to maintain a steady state of plasma concentration and for convenience are often administered in intervals equal to _________
the drug’s half life
this will lead to a mximum two-fold fluctuation in the drug’s plasma concentration which is seen as acceptable in most cases
By definition, drugs delivered by the IV route have ____% bioavailability
100%
Drug clearance (Cl) is defined as:
The volume of body fluid from which the drug is removed per unit time.
an antagonist that binds to a receptor irreversibly through covalent bonding is said to be _________
non-competitive
In the dose-response relationships shown here, drug B would act as a ___________ in the presence of drug C
antagonist
Drug B is an incomplete agonist and will act as a competitive inhibitor in the presence of a drug with higher efficacy
In general, acidic drugs bind to plasma _________
albumin - A for Acid and Albumin
npo means:
nothing by mouth
“nil per os”
ED50 is used to measure _________ (potency / efficacy) and is defined as:
ED50 (median effective dose) measures drug potency and is the dose that produces 50% of the maximal effect of the drug
qh means
every hour
“quaque hora”
Drugs that are eliminated by Zero-order kinetics have a _______ (constant / variable) half-life and a ________ (constant / variable clearance) relative to plasma concentration of the drug.
variable half-life and variable clearance. The half-life is proportional to plasma concentration while the clearance is inversely proportional
desensitization/tachypylaxis is a ________-term adaptation to exposure to a drug, while down-regulation is _________-term reaction
desensitization is short term, down-regulation is long term
Aqueous diffusion of a drug is limited by __________
Molecular weight (only small molecules can diffuse through aqueous pores)
A drug that has affinity for a receptor and only incomplete efficacy is a(n) _________
partial agonist
pc means
after meals
“post cibum”
Weakly acidic drugs absorb best in the (stomach / intestine)
intestine - there is a greater surface area available for diffusion, which is more important than acid/base ionization effects
ex aq means:
in water
bid means
twice per day
“bis in die”
The organs most involved in excretion are the _____
Kidneys
Phosphorylation of receptors in response to repeated exposure to ligand is an underlying mechanism of
____________
desensitization
phosphorylation may reduce the affinity of ligand for receptor or may mark the receptor for cellular internalization, reducing receptor density on the cell surface
Define enterohepatic cycling
The phenomenon whereby drugs excreted through the biliary pathway are metabolized by gut flora and reabsorbed into the circulation
The main purposes of biotransformation are:
reduce the toxicity of drugs and make them more soluble to facilitate excretion
Describe what a prodrug is and why it may be given
a prodrug is inactive until metabolized by the body. It may be given because the prodrug molecule is better absorbed than the active molecule (ex: elanapril).
The time indicated by E in this drug plasma concentration curve is called ______ and represents _____
Onset represents the time after drug administration until the MEC is reached, i.e. the time until a measurable therapeutic effect is observed
compare and contrast the therapeutic index (TI) and certain safety factor (CSF) of a drug
Both are measures of a drugs safety in relation to its potency
Therapeutic index (TI) is the ratio between LD50 and ED50
Certain safety factor (CSF) is the ratio between LD1 and ED99 of a drug. It is a more restrictive and perhaps more practical measure of the safety of a drug.
A drug that has both affinity and efficacy with a receptor is a(n) _________
agonist
List the 4 types of drug receptors
- G-Protein coupled (GPCRs)
- Ligand-gated ion channels
- Membrane-bound enzymes
- Intracellular (nuclear)
qd means:
every day
In the dose-response relationships shown here, ED50 of drug B is ______
1 mg/kg
Compare and contrast G-Protein signal transduction for Gαs, Gαi, and Gαq containing G-proteins
All pathways are activated by a ligand binding to a GCRP which causes G-protein activation by GTP-binding and GDP release. They differ in the effector system and second messengers used.
Gαs and Gαi either stimulate or inactivate adenylyl cyclase, leading to up or down-regulation of cAMP production
Gαq activates phospholipase C which produces IP3 and diacylglyerol (DAG). These two cause an elevation of intracellular Ca2+
upregulation in CYPs that metabolize opioids in response to chronic opioid exposure is an example of __________ (pharmacokinetic / pharmacodynamic) tolerance
pharmacokinetic
changes in number of enzymes for metabolism is a pharmacokinetic change. Changes in number of receptors is a pharmacodynamic change with regards to tolerance.
To facilitate excretion of a weak base drug, the clinician should target a _____ (acidic/basic) tubular pH
acidic. drugs can not be passively reabsorbed in their ionized form, so the ionized weak base will be excreted more readily.
non rep means:
do not repeat
List three ways that drug receptors are classified:
- Drug specificity
- Tissue location
- Primary amino acid sequence
glucuronosyltransferases, acetyltrasnferases, and sulfotransferases are associated with phase _____ (i/ii) biotransformation
phase ii. phase ii reactions are conjugation reactions and thus all involve a “transferase” enzyme
The time indicated by B in this drug plasma concentration curve is called ______ and represents _____
Tmax represents the time until the maximum plasma concentration (Cmax) of the drug is reached
The organ that is most involved in biotransformation is the _____
Liver
compare an allosteric to orthosteric drug-binding site
allosteric = a different binding site than the endogenous ligand
orthosteric = same binding site as the endogenous ligand
_______ is the ability of a drug to bind with its receptor or target
affinity
When GDP is bound to a g-protein, it is _______ (activated / inactivated)
inactivated
g-protein alpha-subunit activation is marked by GTP-binding
Clearance is defined as _____________
the rate of elimination divided by the plasma concentration
in the presence of a complete agonist, a partial agonist may act as a ______
antagonist through competitive inhibition