I need to know how to get the target concentration quickly and stay stable aroun
ID: 82704 • Letter: I
Question
I need to know how to get the target concentration quickly and stay stable around it
The following compartmental diagram describes a simple system where a drug is administered to the body following a dose D(t), and gets excreted by means of urine at a clearance/elimination rate k_m. If the half life of the drug is 8 hours, explain how the amount of drug in the body changes if you administer the drug (a) as a bolus or (b) as an i.v. drip. What would you do in case of a time-critical scenario, where you needed the drug to reach the target concentration quickly, but also stay stably around it? Use equations and graphs (approximate) to explain.Explanation / Answer
The average concentration at steady state is the total exposure over one dosing interval divided by the time of dosing interval.AVC= F dose / CL.CL isthe rate of elimnation.
The time to reach steady state is defined by the elimination half-life of the drug.Half way to steady state 50%is one half life. 75% to steady state in second half life. 87.5% to steady state in third half life. 94% halfway to stady state in fourth half life. Thus the above drug has half life of 8 hours. For it to reach 94% of steady state , it would take 32 hours.
If we want to reach the target concentration quickly, a loading dose can be used and then dropping down to a maintenance dose ,that is lower in concentration. This is to maintain the theuraptic level of the drug stably around it. Average steady state or Maintenance dose rate = Target concentration x Clearance.