Randomization prior to informed consent can increase the number of trial participants, but it causes some difficulties. This is not recommended practice. Here's why...

One particular scheme with experimental and standard treatments that has received some attention is as follows. Eligible patients are randomized prior to providing consent. If the patient is assigned to the standard therapy, then it is offered to the patient without the need for consent. If the patient is randomized to the experimental therapy, then the patient is asked for consent. If this patient refuses, however, then he/she is offered the standard therapy. An "intent-to-treat" analysis is performed based on the randomized assignment.

This approach can increase trial participation, but patients who are randomized to the experimental treatment and refuse will dilute the treatment difference at the time of data analysis. In addition, the "intent-to-treat" analysis will introduce bias.

There are ethical problems as well because:

1. subjects are randomized to treatment without having been properly informed and without providing their consent, and
2. subjects randomized to standard therapy have been denied the chance of receiving the experimental therapy.

For all of these reasons, randomization prior to informed consent is not recommended.