Q.why in renal/hepatic disease, maintenance dose is decreased & loading dose is unchanged?

May 25, 2015
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Medical Student
Q. I didn't understand why in renal or liver disease, dosage of the same drug when given as maintenance dose is decreased and when it is given as loading dose is usually unchanged. Is it because maintenance dose passes through liver/kidney but loading dose bypasses liver/kidneys? I know, We can find the difference in their formula but still I couldn't understand it conceptually . In the formula of maintenance dose, there is clearence and in the formula of loading dose there is no clearence.Does this mean, when the drug is given as maintenace dose, there is hepatic/renal clearence and since liver/kidney is damaged, we should decrease the dose to avoid toxicity; AND, when the same drug is given as loading dose, there is no hepatic/renal clearence (or no metablism) and thus doesn't require to decrease dose (dose is unchanged) even when there is renal/liver disease? (From-FA, pharmacokinetics).But, it is really weird to imagine this way. Can anybody pls cast light on this.Thanks.
 
Mar 5, 2014
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Medical Student
Biochemically, have no clue, but from the formula it tells you everything, the loading dose has nothing to do with clearance as maintenance dose does. Thats all i know, and thats what Kaplan pharm said too.
 
OP
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May 25, 2015
70
9
Status
Medical Student
Yup! may be we have to rely on formula to understand their relation. Actually, I wanted to understand it more conceptually, so posted the above question.Anyway, thanks aspiring1015.