Bioequivalence and Bioavailability Forum

Dear kasi!

❝ why we are giving 240 ml of water while administrating the drug.

See this post.
The often claimed ‘rationale’ is the size of the American standard cup (8 fluid ounces = ½ pint = 236.5882365 ml), which is assumed to be taken together with the drug. Another mythical connection exists between this volume and the volume used in the BCS (250 ml). People advocating 240 ml are talking about the solubility of the drug, but often forget that:

• water has a half life of about 10 minutes in the stomach,
  
• such a volume may be unrealisticly high in clinical practice (especially for females, elderly,…),
  
• AFAIK there is not a single study published (e.g., BE of the same formulation given with 240 ml v.s. 100 ml) supporting such a claim (actually I have seen one – unpublished – study of an ASA-for­mu­lation, where BA was 200% if given with only 50 ml compared to 240 ml).

Many regulations suggest 100 ml - 150 ml instead of 240 ml (see this post)!

❝ why we are following physical activity restrictions (2 hours post dose). is this mandatory. is the deviation effect the bioavailability of the drug.

Physical activity influences

• gastric motility (→ absorption) and/or
  
• hepatic blood flow (→ metabolization).

If you don’t standardize physical activity, you may increase intra-subject variability.

❝ why we are following water restriction (1 hr pre dose and 1 hr post dose).

History?

❝ during water restriction can we allow the subject for urination. if not what is the reason.

What else. Do you want them to pee their pants?
Once the drug is eliminated into the bladder, it will never be reabsorbed. So why not empty it?