Just make sure you're not swapping out one slog for another. Is it that you lost interest in the material, or that it's the amount of work required to pursue it? I doubt that you're going to find medicine less mentally (and physically) demanding.

I started a PhD and found that I just didn't love it enough. I think one's innate curiosity and drive regarding the investigation the subject matter needs to outweigh the undesirable aspects of the pursuit. I saw other people absolutely driven by their work, and they basically sailed through. The others who found it more of a chore often completed the program but then left the field.

It sounds like you and your program are not aligned.

The way you frame it, it almost seems like a no-brainer to switch. Perhaps that kind of work is just something you're more comfortable with. You can try these deep, introspective thought experiments, but I know it's hard to really know without actually doing it. The grass is always greener on the other side. Sometime it actually is.