I was a PA for 3 years before I went back to (US allopathic) medical school. In my class, there was another PA, 3 RNs and a respiratory therapist, so it does happen.
Personally, I think I had more difficulty with the M1 year (basic science) than my traditional classmates. They were used to being gunner students, and I had been out of the classroon for a few years and you'd be surprised how dusty your study skills can get! Plus, a lot of those classes, while important for your foundation of medical knowledge (biochem, embryology, histology, neuroscience, anatomy, physiology) much of it is not material you will actively use as a physician on a daily basis. Most of the traditional students thought M2 (clinical science) was more difficult, but more interesting than M1. I thought M2 was far easier, and my grades were significantly higher with less time/effort than M1 year, as many of the classes that year were akin to the classes I took in PA school (pharmacology, pathology, immunology, etc.). Where I and the other experienced med students really came into our own was in the M3 and M4 years. I had already done these rotations in PA school (the clinical year is virtually identical to the M3 year) so I had at least seen everything before, and through my previous work as a PA I was comfortable seeing patients and had a good idea how to efficiently work as a member of the "team" and you would be amazed at how far this can go in your grading. Plus knowing how to do an H&P and being able to interpret labs, read x-rays, etc. really freed up a lot of my "study" time. Incidentally, it is your M3 year that weighs heaviest into your class rank and is essentially the only grades that residency programs will look at with earnest. I also worked part time (10-20 hrs/wk) as a PA through medical school as well and made some $$ while keeping my skills sharp.
I'll end up graduating in the top of my class, AOA, etc. My Step 1 scores were pretty average, Step 2 significantly better since they were similar to the PA boards I had at one time studied for and passed. Incidentally, I was concerned that in residency interviews they would question my commitment to any medical career field and was worried this would be a detriment to my application, however I have heard nothing but positive feedback about my prior experience in my residency interviews.
I will say that in my experience being a PA offered me zero leg up on actually being admitted to medical school, but it definitely made a lot of difficult and stressful things a lot easier once I was in med school. Be aware that you will get zero credit for your prior experience--you will have to go through every beginner physical diagnosis class, small group discussion, etc. but if you view it as a nice chance to review/practice and one less thing to stress out about, it is not time wasted. In extended conversations with the other PA in my class, I think he has had a similar experience. The verdict is kind of split on the RNs--one did extremely well, one did solidly average and the last failed. Ultimately I think that your experience will help in certain areas, may be a hinderance in others but it is going to be the type of person and student that you are that will ultimately determine how successful your will be in medical school, just like your traditional colleagues!
Feel free to ask any other questions you have/PM me. And for what it is worth, I have never regretted my decision to go back to medical school. I think the PA profession is a wonderful profession and I hope to be involved in PA employment and education as I progress in my career, but it was just not the right match for my professional goals. Follow your heart and remember--you can't stop the time. In 10 years you will still be 10 years older than you are now. Where do you want to be at the end of those 10 years?
