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Imph ★ 2023-06-27 15:06 (469 d 17:55 ago) Posting: # 23621 Views: 2,736 |
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Hi, can you scp enlighten me on how to choose the Cmax in the presence of a profile with two peaks or more? Thank you in advance. |
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dshah ★★ India, 2023-06-27 15:13 (469 d 17:48 ago) @ Imph Posting: # 23622 Views: 2,368 |
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Hi ImpH! Cmax is defined as highest concentration obtained after dose irrespective of number of peaks. The peaks can be observed due to various reason like enterohepatic recirculation and many more. Regards, Divyen |
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Imph ★ 2023-06-27 15:26 (469 d 17:35 ago) @ dshah Posting: # 23623 Views: 2,354 |
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❝ Cmax is defined as highest concentration obtained after dose irrespective of number of peaks. The peaks can be observed due to various reason like enterohepatic recirculation and many more. Thank you for you quick response. So I have to choose the peak showing the highest concentration among the two? |
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Helmut ★★★   Vienna, Austria, 2023-06-27 15:44 (469 d 17:17 ago) @ Imph Posting: # 23625 Views: 2,397 |
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Hi Imph, ❝ ❝ Cmax is defined as highest concentration obtained after dose irrespective of number of peaks. The peaks can be observed due to various reason like enterohepatic recirculation and many more. ❝ ❝ […] So I have to choose the peak showing the highest concentration among the two? Read what Divyen stated above again. By definiton the highest concentration!  — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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Imph ★ 2023-06-27 17:18 (469 d 15:43 ago) @ Helmut Posting: # 23626 Views: 2,342 |
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❝ ❝ […] So I have to choose the peak showing the highest concentration among the two? ❝ ❝ Read what Divyen stated above again. By definiton the highest concentration! yes logically, the issue is that I have read that some softwares systematically take the first peak to define the cmax. |
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Helmut ★★★ Vienna, Austria, 2023-06-27 17:24 (469 d 15:37 ago) @ Imph Posting: # 23627 Views: 2,351 |
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Hi Imph, ❝ ❝ Read what Divyen stated above again. By definiton the highest concentration! ❝ ❝ yes logically, the issue is that I have read that some softwares systematically take the first peak to define the cmax. Which one? I’ve tested 17 (both commercial an open-source). Would be crazy! — Dif-tor heh smusma 🖖🏼 Довге життя Україна! Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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Imph ★ 2023-06-27 18:56 (469 d 14:05 ago) @ Helmut Posting: # 23628 Views: 2,327 |
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Hi, In the WinNonlin guide, this is how tmax is defined: Tmax: Time of maximum observed concentration. For non-steady-state data, the entire curve is considered. If the maximum observed concentration is not unique, then the first maximum is used |
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Helmut ★★★ Vienna, Austria, 2023-06-27 19:03 (469 d 13:58 ago) @ Imph Posting: # 23629 Views: 2,333 |
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Hi Imph, ❝ In the WinNonlin guide, this is how tmax is defined: ❝ ❝ Tmax: Time of maximum observed concentration. For non-steady-state data, the entire curve is considered. If the maximum observed concentration is not unique, then the first maximum is used Sure, but you were talking about Cmax – not tmax. That’s how it is implemented in all software I know. During a training a smart-ass said “That’s all wrong! If there are identical maxima, tmax should be reported as the median of observed times.” I think that’s a rather academic question. How likely is it to have exactly (‼) the same concentrations? — Dif-tor heh smusma 🖖🏼 Довге життя Україна! Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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Imph ★ 2023-06-27 19:33 (469 d 13:28 ago) @ Helmut Posting: # 23630 Views: 2,399 |
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❝ ❝ Tmax: Time of maximum observed concentration. For non-steady-state data, the entire curve is considered. If the maximum observed concentration is not unique, then the first maximum is used ❝ ❝ Sure, but you were talking about Cmax – not tmax. That’s how it is implemented in all software I know. Yes but the Cmax was defined accordingly: Cmax: Maximum observed concentration, occurring at time Tmax, as defined above. When reading this, we can easily think that the software would take the first peak as Cmax. Edit: Full quote removed. Please delete everything from the text of the original poster which is not necessary in understanding your answer; see also this post #5! [Helmut] |
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BEQool ★ 2023-06-27 20:25 (469 d 12:36 ago) @ Imph Posting: # 23631 Views: 2,307 |
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❝ ❝ ❝ Tmax: Time of maximum observed concentration. For non-steady-state data, the entire curve is considered. If the maximum observed concentration is not unique, then the first maximum is used ❝ ❝ Yes but the Cmax was defined accordingly: ❝ ❝ Cmax: Maximum observed concentration, occurring at time Tmax, as defined above. ❝ ❝ When reading this, we can easily think that the software would take the first peak as Cmax. Hello Imph, if I am not mistaken, I think that you may be mixing peaks with maximums (maximum ≠ peak)? You may have multiple peaks in a profile but normally (almost always) just one maximum concentration and this one maximum concentration defines Tmax. Just in extreme rare cases when you have two identical maximum concentrations (not just two peaks but two peaks with the same highest concentration) at different sampling time points, the software (WinNonlin) uses first highest concentration (Cmax) sampling point as Tmax. |
Ing. Helmut Schütz