Kinetics 11.5 - 14.5 Flashcards
TIME COURSE OF DRUG EFFECTS
Effect is not linearly proportional to the concentration.
IMMEDIATE EFFECT
TIME COURSE OF DRUG EFFECTS
Due to distributional delay
Changes in drug effects are often delayed in relation
to changes in plasma concentration
DELAYED EFFECT
TIME COURSE OF DRUG EFFECTS
Directly related to concentration
Because the relationship between drug concentration and effect is not linear the effect will not be linearly
proportional to the concentration
IMMEDIATE EFFECT
TIME COURSE OF DRUG EFFECTS
Delayed expression of the physiologic substance
needed for the effect
A common reason for more delayed drug
effects—especially those that take many hours or
even days to occur—is the slow turnover of a
physiologic substance that is involved in the
expression of the drug effect
DELAYED EFFECT
TIME COURSE OF DRUG EFFECTS
Constant infusion
CUMULATIVE EFFECTS
TIME COURSE OF DRUG EFFECTS
Aminoglycosides causes renal toxicity if given constantly
The effect of many drugs used to treat cancer also
reflects a cumulative action—eg, the extent of
binding of a drug to DNA is proportional to drug
concentration and is usually irreversible.
CUMULATIVE EFFECTS
TIME COURSE OF DRUG EFFECTS
Intermittent dosing only
CUMULATIVE EFFECTS
Plan for drug administration over a period of time
DOSING REGIMEN
Achievement of therapeutic levels of the drug in the body without exceeding the minimum toxic concentration
DOSING REGIMEN
Goal is to achieve therapeutic levels: maximal effect,
least
DOSING REGIMEN
DOSING REGIMEN
Based on therapeutic window
Toxicities
DOSING REGIMEN
to maintain plasma
concentration over periods of time
Maintenance Doses
DOSING REGIMEN
to achieve target plasma level rapidly
Loading Dose
is based on the assumption that there is a target concentration that will produce the desired therapeutic effect.
By considering the pharmacokinetic factors that
determine the dose-concentration relationship, it is
possible to individualize the dose regimen to
achieve the target concentration.”
rational dosage regimen
a poisonous compound present
in the foxglove and other plants
digoxin
Desired therapeutic effects are produced
In the achievement of this therapeutic levels the
drug without causing adverse reactions
TARGET CONCENTRATION
It is a steroid glycoside and is used in small
doses as a cardiac stimulant
digoxin
is the concentration that
reflects a balance between the beneficial and
adverse effects. ”
TARGET CONCENTRATION
Doses per day is determined by:
○ Half life
○ Therapeutic window
Maintenance/Loading
MAINTENANCE DOSAGE
Maintain a concentration higher than minimum therapeutic level at all times
Maintenance/Loading
MAINTENANCE DOSAGE
Dose needed to maintain a steady state of concentration
Maintenance/Loading
MAINTENANCE DOSAGE
Maintain plasma concentration within a specified range over long periods of therapy
Maintenance/Loading
MAINTENANCE DOSAGE
Enough drugs to replace eliminated drugs
Maintenance/Loading
MAINTENANCE DOSAGE
is the most important parameter defining rational drug dosage
Clearance
is the most important pharmacokinetic
parameter to be considered in defining a rational steady-state drug dosage regimen
Clearance
is large, the dose should be given
slowly to prevent toxicity due to excessively high plasma levels during the distribution phase.
Maintenance/Loading
Loading Dosage
For drugs with long half-lives and longer time to
reach a steady state
Maintenance/Loading
Loading Dosage
Given to promptly raise the concentration of the drug to the target concentration
Maintenance/Loading
LOADING DOSAGE
LOADING DOSAGE
T/F: If the therapeutic concentration must be achieved rapidly and the volume of distribution is large, a large loading dose maybe needed at the onset of therapy
True
It takes how many half lives to reach a the steady state
For example your drug needs a 12 hour half
life it means that you will need to wait 48 hours for it to reach the steady. So hindi ka pwede magantay ng mahabng oras, for example infection, bacteria in just a few hours will already multiply, if you will wait 24-48 hours maybe the immune system of the patient will already
succumb.
● That’s why loading dose are given to increase and
raise the concentration to the target effector levels.
Here what is important in the primary parameter
would be the volume of distribution of your drug.
4
THERAPEUTIC DRUG MONITORING
PHARMACOKINETIC VARIABLES (4)
- ABSORPTION
- CLEARANCE
- VOLUME OF DISTRIBUTION
- HALF LIFE
