Actually, these are two entirely different medications. Campral is Acamprosate and Naltrexone is also known as Revia and Trexan. See this link:
http://www.aafp.org/afp/20051101/1775.html
Naltrexone blocks the opiod receptors, as stated earlier, and Campral "Acamprosate (calcium homotaurinate) is believed to block glutaminergic N-methyl-d-aspartate receptors and activate g-aminobutyric acid type A receptors, and was recently approved by the FDA for the treatment of alcohol dependence"
I was also following the program in Seven Weeks to Sobriety and taking Glutamine, and my Dr said the Campral worked on the similar theory as the Glutamine replacement therapy in Seven Weeks to Sobriety.