Suppose you want to achieve a plasma concentration for a drug, say penicillin, of 1 mg/L. How much of the drug would you have to administer, say i.v., in a 70 kg person?
(Ignore the fact that as soon as you give something elimination kicks in right away so that you would be chasing an elusive point in time...).
If you feel that you cannot calculate or estimate this and need some more information to do so, what information do you need - or what assumptions are you making to make your estimate?
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ReplyDeleteI messed up the first time so here is round two.
ReplyDeleteI will start with the assumptions-
:20% of their total body weight is ECF (14L)
:3L of the ECF is plasma
:IV administration (with 100% bioavailability)
Therefore if the drug were to stay in the blood only 3mg would need to be administered. But since drugs that stay in the blood are not as widely useful except to maybe target blood.
However another assumption based can be made-
:Drug passes into interstitial fluid (more likely)
In which case 14mg would need to be administered.
Even more if the drug is taken up by cells.