Lamisil can cause liver damage (sometimes severe), that is why your friend's doctor does not want him to continue taking it long-term. Hopefully, the treatment he has received so far will do the trick.
Should your friend notice that the infection appears to be coming back, have him try Vicks VapoRub, applied directly to the nail. I know it sounds strange, but MANY people have had success using it. I have been using it myself on a toenail that has been infected for years, and after about 3 weeks of use, my nail is looking very healthy again. This treatment needs to be continued every day until ALL of the affected nail has been completely cut off (which can take several months to a year or so, as toenails grow very slowly). Leaving even a tiny amount of affected nail can cause the fungus to take hold again.
This subject was discussed in detail a few weeks back on this board--go back a couple pages and you will find it.