True an MBA program can be completed as an evening program but at what cost? You spend all day working, and then you have to attend 3 hour long classes. Don't forget the additional studying. And you're going to see your family when? One recent evening MBA student I spoke with described it as "three years of hell."
In fact, I view the MBA between your 3rd and 4th years as the best from an educational standpoint for several reasons:
1. You're still in studying mode. How much do you think you'll feel like studying when you've been out of school for 5, 10 years?
2. You'll only add 1 year on to your total schooling whereas an evening or executive program can add 3+ years on. Despite only adding 1 year, you'll get the 2 year experience. Many programs have you do an additional semester or evening classes during your final year of clinical medicine in the med school.
3. You will be able to view healthcare from both a clinical and business perspective. Something that is not easy for a 40 year old doc who has only seen healthcare from one perspective their whole life.
4. Especially if you have worked before or you plan to do an internship, you will be able to apply what you've learned immediately.
Now, if you have never worked before, then the MBA is questionable and you can ignore my above advice