Gender swap pill accident

After two close friends purchase a monthly supply of attractive blonde bimbo DNA alteration pills.
Both friends came to an agreement.
The friend who lost at rock, paper and scissors would take the 
 24 hour pills each day for a week.
While the winner would be able to use the losers female form
as a sex object. 
Basically giving the other the freedom to penetrate every orifice on the female body.
Upon completion of that week the winner then is required to take
the pills for a week with the same stipulations.
Each friend takes turns becoming female while being fucked senseless.
However the winner of the contest was fully aware of the side effects of the chemicals in the pills.
These FDA approval pending pills have a warning that says

Warning: Ingestion of semen will cause DNA freeze.
1/4 chance of complete DNA freeze and permanent gender lock.

Which is why he waited until the friend who lost the contest was on the last day of the month and during the last two hours of her transformation before he restrained her and vigorously fucked her mouth until he ejaculated in her mouth six times before tossing the empty box at her feet revealing what just occurred.