Potion of Cowardice and Enthrall

[Videophile]

I have a question about the potion of cowardice. My friend was a bard and was in combat against a monster he could not beat. He then said “I am going to try to enthrall someone”. At that point, I played the potion of cowardice and said that he has to run away. My friend thought that since he already announced that he was going to enthrall someone, he should roll the die and see if the enthrall worked, and that if it did, the potion of cowardice will now effect both people in combat. I thought that he can’t enthrall anymore and has to run away. Which is it?

Thanks!