Bioequivalence and Bioavailability Forum

ioanam ★ Romania, 2010-01-30 12:13 (5638 d 10:23 ago) Posting: # 4667 Views: 6,867	prediction of steady state concentration [PK / PD] Post reply
	Dear all, There are different formulas to predict steady state parameters with known single dose data. The PK equation (http://www.summitpk.com/equations/equations.htm#P3) describes calculation of Cmax(ave) and Cmax(ave)(area). Which is the real difference between these two parameters? They don't need to have the same value? Thank you. Kindest regards, Jo

Helmut
★★★

Vienna, Austria,
2010-01-30 16:06
(5638 d 06:30 ago)

@ ioanam
Posting: # 4669
Views: 5,376

prediction of steady state concentration

Post reply

Dear Jo!

❝ The PK equation describes calculation of Cmax(ave) and Cmax(ave)(area).

❝ Which is the real difference between these two parameters? They don't need to have the same value?

Both equations assume linear pharmacokinetics.
The first one gives you the expected maximum concentration (C_max,ss), whereas the second one the average concentration (C_av,ss). Generally C_min,ss<C_av,ss<C_max,ss. The higher the accumulation (i.e., τ « t_½), the closer C_av,ss gets to C_max,ss (or C_min,ss≈C_av,ss≈C_max,ss). In other words, you will get little fluctuation (C_max,ss – C_min,ss)/C_av,ss for high accumulation.
The second equation is a modification of the superposition principle of pharmacokinetics, i.e., AUC_τ = AUC_∞.

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ioanam ★ Romania, 2010-01-30 17:45 (5638 d 04:50 ago) @ Helmut Posting: # 4670 Views: 5,310	prediction of steady state concentration Post reply
	Thank you very much. Jo.

prediction of steady state concentration [PK / PD]

prediction of steady state concentration

prediction of steady state concentration