- On 5 Jun 2004 at 21:46:16, Wajahat (wajih76.aaa.yahoo.com) sent the message
hi,

Back to the Top

i have some confusion about the number of subjects to

be included in a BE study, i went thru the FDA site

but couldnt get over my confusion about the number of

subjects and syudy designs.

actually i want to design a 3 period study in which

two test fomulations will be tested against a

standard, would the minimum number of subjects i.e 12

give enough power to the study?

thanks

wajahat - On 7 Jun 2004 at 09:44:59, fabrice_nollevaux.aaa.sgs.com sent the message
Dear Wajahat,

Back to the Top

For a BE study conducted according to a crossover design, the sample

size should be estimated based on the residual (i.e. intra-individual)

variability of the target parameter (generally Cmax and AUC). This

variability can be estimated from previous studies or sometimes found

in the litterature.

For a detailed overview and also tables of the required sample size in

a BE study with regards to the expected residual variability and to the

expected difference between the test and reference formulations, see:

Diletti E et al. (1991) Sample size determination for bioequivalence

assessment by means of confidence intervals. Int J Clin

Pharmacol;29;1-8.

For example: with twelve subjects, the power in demonstrating BE (Test/

Reference 90%CI within 0.80-1.25 assuming a multiplicative model)

reaches at least 80% only if the intra-individual CV is at most 15%.

Hope this helps ,

Fabrice Nollevaux

SGS Biopharma - Wavre - Belgium

www.sgsbiopharma.com - On 7 Jun 2004 at 05:57:23, tausif Ahmed (mailtaus.-a-.yahoo.com) sent the message
Dear Wajahat,

Back to the Top

The sample size calculation depends on the power of the study and the

intrasubject variability of your drug. FDA recommends 24 volunteers for

2x2 crossover study. But you can use a larger sample size, based on

power and the intrasubject variability of the drug.

regards

Tausif Ahmed

Dept. of Pharmaceutical Medicine

Ranbaxy CPU, Hamdard University,

Delhi, India

Want to post a follow-up message on this topic? If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Number of study subjects" as the subject

PharmPK Discussion List Archive Index page

Copyright 1995-2010 David W. A. Bourne (david@boomer.org)