My unmedical logic based opinion would be that consuming a drug which 'relaxes' could affect the decision making process regards slower drinking. I believe that in humans Nal lets you recognise the fact that you actually don't want to drink more and thus stop at a certain point. I shall try and find something out about this.
Right I've just found this and Dr Eskapa's response is at the bottom, it is a few years old so don't know if anything has changed in the meantime;
viewtopic.php?f=15&t=349The benzodiazepines will not help you with the Sinclair Method - they will hamper, slow, and weaken your de-addiction or extinction progress. Avoid them if at all possible. There is both scientific research to support this and also clinical cases ....