If it's anything similar than the drug they use to prevent getting the virus when someone has had a potentially dangerous event with a HIV positive person (and it must be very similar) then yes, the side effects are not very nice.
With pre-exposure prophylaxis (PreP), a person typically takes a low dosage of one drug (Truvada was the first drug to be approved for this purpose - it actually combines two drugs in one pill. Other drugs may be approved for PreP in time). A relatively low level of Truvada in a person has proven to be quite effective at preventing an HIV infection from taking hold.
There are potential effects to kidney and bone health, so if you start taking Truvada, you want to do it under supervision of a medical professional who monitors those things. Some people who have been taking truvada have blogged about it, so you can easily get a first hand account of their experience on websites like this one:
http://myprepexperience.blogspot.co.uk/?m=1
Post exposure prophylaxis (PEP) is a little different. This is the emergency intervention that you can do within 72 hours of exposure to HIV. For example, an ambulance crew member who had an injury from a needle (needle-stick) might need PEP. My understanding is that you have a 72 hour window to hit the virus hard before It makes a permanent home for itself in the human body. So PEP involves two or three medications in relatively high doses for about a month. I believe that might come with more side effects than PreP.
Bear in mind that HIV+ people had been taking Truvada (in combination with other medications) for some years before it was approved for PreP. From what I read, it seems that HIV+ people with treatment can expect to live as long as HIV negative people, but they tend to have higher incidences of health problems as they age. How much of that is side effects from medication and how much is a result of the virus, I don't know.
Well, this is about the extent of my understanding. I won't pretend that I know any more but I would encourage you to read about this. I think things are advancing so quickly and it's important not to just assume that PreP must have similar impact as PEP etc.
