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RegisterTime points (infusion) [Design Issues]
posted by Helmut 
– Vienna, Austria, 2010-11-22 15:42 (5700 d 06:20 ago) – Posting: # 6185
Views: 7,831
Dear Kishor!
By tmax 1 hr you mean the duration of the infusion, I guess? We must distinguish whether you will analyze your data by means of NCA or PK modeling. If you go with NCA, I would suggest to take two blood samples prior to 1 hr, namely at ≈15 min an ≈45 min. If you want to perform PK modeling, you don’t have to sample prior to the end of infusion at all - the infusion rate is a fixed parameter and must not be covered by data (although one sample may result in more stable fits). It is of paramount importance to record the actual duration (not the planned one).
For the sampling time points in the elimination phase you must consider the following:
❝ […] time point selection for one of the intravenous infusion formulation having the Tmax 1 hr and Half life 2 hrs.
By tmax 1 hr you mean the duration of the infusion, I guess? We must distinguish whether you will analyze your data by means of NCA or PK modeling. If you go with NCA, I would suggest to take two blood samples prior to 1 hr, namely at ≈15 min an ≈45 min. If you want to perform PK modeling, you don’t have to sample prior to the end of infusion at all - the infusion rate is a fixed parameter and must not be covered by data (although one sample may result in more stable fits). It is of paramount importance to record the actual duration (not the planned one).
For the sampling time points in the elimination phase you must consider the following:
- Based on the lowest expected Cmax in any (!) of the subjects calculate the last time point where you can measure ≥LLOQ. Your elimination rate is kel = ln(2)/2=0.34657.
The time course of post-infusion concentrations (in % of Cmax) is given by Ct = 100·e-kel·(t-tinf), where tinf is the duration of the infusion. Solving the equation for the common requirement of Clast = 5 % of Cmax gives you the last time point of 9.64 hours: tz=[kel·tinf+ln(100/5)]/kel. If your analytical method is able to measure lower values, fine.
- Once you have determined tz, calculate the post-infusion sampling time points according to this algorithm. Plan for as many time points as your budget allows.
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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
Complete thread:
- Regarding Time point selection of IV infusion formulation kishorpatil 2010-11-22 04:50
![[Mix]](https://static.bebac.at/img/mix.png "open in Mix view")
- Time points (infusion)Helmut 2010-11-22 14:42
- Time points (infusion) kishorpatil 2010-11-23 10:54
- NCA = model independent Helmut 2010-11-23 13:57
- Details time points kishorpatil 2010-11-26 09:35
- Ballpark figure(s) Helmut 2010-11-26 12:59
- Ballpark figure(s) kishorpatil 2010-11-29 11:41
- Believes... Helmut 2010-11-29 13:44
- Believes... kishorpatil 2010-11-30 05:56
- Are you serious? Helmut 2010-11-30 15:38
- Are you serious? kishorpatil 2010-12-09 05:10
- Are you serious? Helmut 2010-11-30 15:38
- Believes... kishorpatil 2010-11-30 05:56
- Believes... Helmut 2010-11-29 13:44
- Ballpark figure(s) kishorpatil 2010-11-29 11:41
- Ballpark figure(s) Helmut 2010-11-26 12:59
- NCA = model independent NewInPK 2011-01-31 05:47
- Details time points kishorpatil 2010-11-26 09:35
- NCA = model independent Helmut 2010-11-23 13:57
- Time points (infusion) kishorpatil 2010-11-23 10:54
- Time points (infusion)Helmut 2010-11-22 14:42
Ing. Helmut Schütz