Dosing Regimens Flashcards
What is the goal of dosing regimens?
to achieve and/or maintain a therapeutic concentration while avoiding toxicity
What are different type of dosing regimens?
- single dose (bolus)
- continuous infusion
- intermittent dosing (fixed-dose/fixed time)
Toxicity can be manifested as what?
side effects
What does this describe:
- plasma levels increase as drug distributes until the peak is reached
- levels fall due to metabolism and elimination
single dose
When you give an IV, when will you see the max peak of concentration?
right after you administer the drug
In a single oral dose, what happens?
- you take it once
- after period of time, it reaches its peak
- tapers off over time
In a single IV dose, what happens?
- max concentration occurs at time it is given
- tapers off over time
What is the goal of intermittent dosing?
to achieve a steady-state concentration
How can intermittent doses be given?
oral or IV
How many half-lives does it take to achieve steady-state?
5 half lives
(90% steady-state is 3.3 half-lives)
Where might you see side effects/toxic effects of an intermittent dose?
at the peaks
What is the lowest point on concentration before the next dose in an intermittent dose?
trough
What is an example of intermittent doses?
blood pressure medication - given continuously, patient reaches a steady-state if they are taking it correctly
If we cannot wait 5 half-lives to reach a steady-state, what can we give patients?
loading dose
What is the goal of loading dose?
to achieve a target blood level quickly
What types of drugs are beneficial to use loading dose?
- long half-life drugs
- immediate effect is needed
What describes when a large initial dose followed by maintenance doses to maintain therapeutic blood levels?
loading dose
Does loading dose get a patient to steady-state?
no, it isn’t taken continuously
What is not effective if plasma concentration is independent of efficacy?
loading dose
When will you reach a steady-state?
after 3.3 half-lives
why is there more potential for side effects if intermittent dosing is every 24 hours?
dose is higher
Can you increase the rate of a continuous IV infusion to get to steady-state faster?
no, its always after 3.3 half lives
If there is a longer timeframe between doses of a drug, what happens?
higher dose is given
Increasing rate of drug will increase what?
concentration of the steady state, but WILL NOT effect time to get to steady-state
We expect to see the effect of the drug in who?
most people most of the time
“most people” = young, middle aged adults
Drugs are rarely studied in who?
children and elderly
What should be made with respect to the results seen in the individual regardless of what is seen in the population?
clinical monitoring and adjustments
What is a standard curve showing how concentration changes over time after oral administration of a drug?
concentration vs time curve
What is AUC?
area under the curve
What measures the total exposure to drug after a dose?
area under the curve
Drugs/total drug exposure can be what % off under the curve?
20%
What is Cmax?
maximum concentration of drug/peak effect of drug you will get
What is MEC?
minimum effective concentration (concentration needed to see a minimum effect)
What is tmax?
time it takes to reach maximum concentration
What is the lag period?
period of time after administration where it is not working
What can be the same for IV, oral, and extended release drugs?
area under the curve
What is used to demonstrate the expected response to a given dose of a drug?
dose-response curve
What includes the range of concentrations needed to demonstrate a relationship is so great a semi-log plot is used rather than the linear format?
dose-response curve
Linear formatted dose-response curves are hard to determine what?
different concentrated, so log plots are used to get a better range of concentration
What is the dose required to produce a response?
potency
What does potency of a drug depend on?
its affinity
What describes the strength of binding between a receptor and its substrate (how much does the drug like the receptor)?
affinity
What is measured by Kd (equilibrium dissociated constant)?
affinity
What does a high Kd value mean?
low affinity, so strength of binding between receptor and substrate is decreased, so potency is decreased (will take longer to reach desired efficacy)
What does a low Kd value mean?
high affinity, so strength of binding between receptor and substrate is increased, there will be a stronger response, and potency will increase
Two drugs do the same thing, but one requires 5 mg to be effective (drug A), and the other requires 20 mg to reach same effectiveness (drug B), which is more potent?
Drug A
What is EC50?
concentration of drug that produces half the maximal effect
What is used to identify the relative potency of a drug?
EC50
What is helpful in comparing potencies of drugs that are designed to produce the same effect?
EC50
How is EC50 determined?
in a test tube (in-vitro comparison)
What is described as the maximum effect a drug is capable of producing (how much of an effect after drug binding)?
efficacy
What is described as the degree to which a response is achieved?
activity
What is Emax?
maximal effect of drug
