Hi rajasmom and welcome to the group! This what I wrote about mg & side effects of Nal on the General Discussion board, I suggest you do some reading on this Forum as there is a lot of information here.
The Cure for Alcoholism: The Medically Proven Way to Eliminate Alcohol Addiction book and TSM state that there are no or very little side effects but from my experience and reading others posts on this site,it appears many have some sort of side effects. I am not trying to scare any newbies as they may not have any side effects at all but as I say from what I have been reading some people are giving up in the first week or so without even giving Nal a chance. I am just writing this in hopes that others don't have to go through side effects feeling alone and know that they do diminish in days or weeks.
I am not an expert by any means but my suggestion would be as follows.
If taking Naltrexone I would ease your system into taking this by starting with 12.5 mg for a few days, then upping to 25 mg for a few days and finally taking 50 mg. I would also say to take with food and lots of water at first which can help with any nausea (Nalmefene, cannot be split up). I actually cannot even take my vitamins on an empty stomach or I will be sick.
OK just my 2 cents but hopefully that helps some people new to TSM.
Also I would recommend you read the book "The Cure for Alcoholism: The Medically Proven Way to Eliminate Alcohol Addiction" and as TSM firmly states and everyone else on this Forum to ALWAYS follow the Golden Rule, never Skip Nal before drinking!

Here is a link from the documentary "One Little Pill" that you can either rent or purchase which Claudia Christian made:
http://www.onelittlepillmovie.com/