Drinking less, or quitting altogether, is of course something you have to do yourself. There is no magic pill that can do it for you. Sometimes people take medication as support. These medications are only available by prescription, and should only be taken as support in addition to other help and/or therapy.
Librium® (chlordiazepoxide) is sometimes prescribed to relieve the withdrawal symptoms. This is only necessary if you expect real, physical withdrawal. Since it too is addictive, you can only use it for a few days.
Campral® (acamprosate) diminishes the desire to drink. It has been on the market for several years, and studies have shown that it is effective in combating craving for alcohol in combination with therapy.
Refusal® or Antabus® (disulfiram) is an aversion (or deterrent) therapy. A person drinking alcohol while taking this substance becomes nauseous and vomits. The idea is that the medication is taken daily, and the fear of the reaction is the deterrent to continued drinking. Given the severity of the reaction, this medication should only be taken if you're physically fit, for example, if you have no heart problems.