The 28-year-old former Scotland A cap was shown a yellow card 12 minutes into the 28-14 loss at Thomond Park following a shoulder charge on Jack O’Donoghue.
While McKenzie was making his way to the sin-bin, his victim left the field on a stretcher and he has been now been charged by Guinness PRO12 disciplinary chiefs with putting his opponent’s safety at risk.
A disciplinary hearing will be held in Cardiff on Wednesday, where McKenzie could face a lengthy ban.
O’Donoghue was knocked out by the blow he took to his neck but Munster director of rugby Rassie Erasmus confirmed the injury was not as bad as first feared.
However, he called on PRO12 bosses to make an example of McKenzie.
Speaking after the match, Erasmus told theJournal.ie: “It looks okay. Jack went to hospital. I’m not sure of the results, he is sitting in the changing room. He is very sore and stiff. I guess it can’t be too serious if he is back in the changing room again.
“It was his neck, I’m not sure how much of concussion was involved. Neck and head, you have to be very careful when it comes to that.
“But it’s foul play and a guy got knocked out. If we allow that to happen then a lot of guys will get knocked out.”