02- Dosing Regimens Flashcards
Toxic Range
range in which a certain plasma concentration of a drug produces toxicity
Therapeutic Range
range in which a certain plasma concentration of a drug exhibits the desired therapeutics effects of the drug
Ineffective Range
range in which the plasma concentration of a drug is too low to see any therapeutic effects of the drug
-not enough drug activating receptors to produce a response
Minimum Effective Concentration (MEC)
the lowest plasma concentration of a drug that produces an observable response
Css
average steady state plasma concentration
-usually desired within the therapeutic range
Bioavailability (F)
fraction of drug reaching the systemic circulation in its active form
-IV has bioavailability of 1
AUC
area under the curve, used to measure bioavailability of a drug?
Onset of Action
how long it takes after administration of a drug to see the desired effects of the drug (how long does it take plasma concentration to reach MEC)
Duration of Action
how long plasma concentration of a drug stays above MEC
-measured from onset of action to end of action
Apparent Efficacy
the efficacy that is seen in the patient and is variable from person to person
-reflective of the peak plasma concentration achieved by certain drug dose and its observed effect
Rate of Availability
rate at which drug enters systemic circulation
-affects onset of action and can affect apparent efficacy and duration of action
Volume of Distribution (Vd)
the apparent volume in which a drug distributes
Vd= Amount of drug in body (bioavailability x administered dose)/plasma concentration (Cp)
Clearance (CL)
elimination of active drug after its distribution
CL= Rate of elimination/Cp (plasma concentration)
-includes elimination by excretion and metabolism
1st Order Elimination
delivery-limited elimination where capacity is not saturated so elimination is dependent on Cp
- percentage eliminated is constant but amount eliminated is variable
- CL is usually constant
“0” Order Elimination
capacity-limited elimination where capacity is saturated and constant amount of drug eliminated per unit time (percentage eliminated variable)
-rate of elimination independent of Cp, and CL is variable
Loading Dose- D(L)
dose given to quickly attain Css by filling Vd
- dose dependent on Vd which is proportional to body weight
- D(L)= (Css x Vd) / F
Maintenance Dose- D(M)
dose given to maintain Css by replacing loss due to elimination
-dependent on elimination
D(M)= [(Css x CL) / F] x dosing interval
Rate of elimination= (Cp x CL)
Dosing Frequency (interval)
interval in which a certain dose of drug is given to maintain Css in therapeutic range
-dependent on clearance (CL) which relates to drug half-life (t1/2)
Drug Half-Life (t1/2)
time required for plasma concentration of drug to decrease by half
t1/2= (0.693 x Vd) / CL
Target Effect Strategy
dosing strategy is which a drug dose is titrated to achieve a desired therapeutic effect in a patient
-use effect that you see in the patient to decide whether to increase or decrease a given drug dose
Target Concentration Strategy
dosing strategy in which a drug dose is titrated to achieve a specific plasma concentration
-used when an effect cannot be readily determined or with a drug that has a low T.I.
Maximal Dose Strategy
dosing strategy in which highest allowed dose is initially given
-used with drugs that have a high T.I.
Plateau Effect
the effect normally seen after administering 4 to 5 half-life doses in which further administration of half-life doses does not cause an increase in the Css
Cp(0)
apparent plasma concentration at time 0
- used to determine Vd
- can only be observed mathematically because requires instantaneous absorption and distribution, and no metabolism
