Hi,Back to the Top
In drug distribution studies, is there any guideline for the time
period for collecting the tissues and analyzing the drug in those
tissues? I am not able to understand at what different time points one
should collect the tissues and try to analyze the drug in order to get
tissue distribution profile of a drug?
hi thereBack to the Top
well i am sure that you must have performed oral pk studies of your drug
before you are planning to do the tissue distribution studies. In that case
u must plan an initial pilot study using the same time points as that
of oral study. This study should give you a faily good idea to proceed
further. BTW all this is fine to do if you are using rats for your study.
vipul kumar gupta
Dear JimmyBack to the Top
For doing Tissue distrubution studies in rats, following step would be
First decide the route of administration, and carry our plasma / serum
profiling of the drug. Time points should be sufficient enought o
catch Tmax and fair calculation of T1/2.
Once you know Tmax and T1/2, after two to three trial ( in order note
the variation intra day in preclinical species) you can select time
point like below
zero sample, 1/2 Tmax, Tmax, 2 Tmax, T1/2, 2T1/2, 3T1/2 and 5T1/2.
These samples would be enough to catch Tissue Cmax and Tmax levels.
After initial experiments, after lookingat results,you can refine
these time points.
With Besh Wishes
Vishwottam K N
Scientist - Biopharmaceutical Research
Suven Life Sciences Ltd
Road # 7, Banjara Hills
Hyderabad - 500034
Phone : 91-40-23556039 / 23541142
Fax : 91-40-23541152
Back to the Top
Hi Jimmy, I think the tmax would be the ideal point for collecting the
tissues. at this time i think there is enough drug in the circulation to
give the exact picture of the correct distribution of the drug in the
different tissues. i hope this helps, thank u,bye,Jagannath Kota
Dear Jimmy and Jagannath:Back to the Top
What is the reason that the Tmax would be the best? Why notuse
D-optimal design, or some similar approach, to compute the times at
which the information is optimal for the structural model, containing
at least a central (serum) and a peripheral (tissue) compartment, and
the parameter values you have? I think this would be much better, and
it would be based on good math, not just opinion.
D-optimal design finds the times at which changes in the
various parameter values cause the greatest changes in serum
concentrations, so one can best see through all the various
uncertainties in the study and get the most precise parameter
estimates. Other optimality criteria are also used, but D is very
strung, has been around for over 30 years, and has a very good track
record. A reference is:
D\0x12Argenio D: Optimal Sampling Times for Pharmacokinetic Experiments. J.
Pharmacokin. Biopharmacol., 9: 739-756, 1981.
Very best regards,
Roger W. Jelliffe, M.D. Professor of Medicine,
Division of Geriatric Medicine,
Laboratory of Applied Pharmacokinetics,
USC Keck School of Medicine
2250 Alcazar St, Los Angeles CA 90033, USA
Phone (323)442-1300, fax (323)442-1302, email= jelliffe.at.usc.edu
Our web site=http://www.lapk.org
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