Hi All,

I am new to clinical pharmacology, so there may be some wrong assumptions/interpretations in my logic of reasoning the questions. Please kindly correct me if that's the case. I have a hard time interpreting the following two concepts.

__AUMC (area under first moment curve)__

1. Is first moment the same as first order (kinetics), or if they are related in any way.

2. What information can I extrapolate from AUMC vs t curve? The y-axis is C*t, which is the AUC of concentration vs t curve [AUC (C*t) = overall exposure by definition]. In other words, AUMC would give me exposure vs t. Then, what would we learn from this exposure vs t curve?

3. Its equation is **integral t*C(t) dt____0-infinity**. What is the end product of this integral? Is it **[C(t)*(t^2)] / 2**?

__MRT (mean residence time)__

1. Residence time literally means the time of a drug stayed in one's body. I start to not follow the logic when we talk about the mean of residence times.

Let's say we give the exact same drug to a patient 10 times, and we measure the residence time of each. What is the process like? Do we give the patient the drug after the drug has been eliminated from the system completely, or at least 4-5 half lives? Or do we give the patient the drug 10 times at once?

-If it's the former scenario, why would the residence time be different each time? Is it due to intra-subject variability? If yes, what could those variables be?

-If it's the later scenario, assuming no intra-subject variability, non-linearity seems to be a reasonable guess for the observed difference in residence times. However, MRT is under the principle of first order elimination, which is linear in terms of the % of drug eliminated. Or is this exactly why the residence times are difference? Because it eliminates drug at the same % over time, not the same amount?

Thank you!