Not sure. But, in the US, it is a preventative prescription-only medication taken in advance - not once symptoms appear.

Hiring a car and driver is relatively cheap. We took trains between cities and hired a new car/driver in each city (well tuk tuks sometimes). So, I can't speak too much about countryside driving. But, I am also very comfortable driving on the left and that has nothing to do with why I, personally, would simply hire a driver for the whole trip over driving a rental car myself. IIRC, One could hire a car and driver in Delhi to drive all around the Golden Triangle for $400/week or less and that driver would also take you to each attraction in each location (so, you would not have to hire separate local taxis).

Whatever you decide, I am sure you're going to have a good time. India is a destination that I definitely appreciate more after returning home.

Also, read up on scams by touts of you haven't already. India was definitely a place where I felt like a mark for scams more than anywhere else.