What happens when you drink alcohol with methadone?

I know someone who drinks heavily e.g. a bottle of wine or more a day. They are on a highish dose of methadone, diazepam,anti depressants , risperidone,and other pills, not sure what. They have been complaining of blackouts and hearing voices. Also displayed paranoid behaviour. Dunno if it is the drug cocktail, as this person is possibly schizophrenic also. The anti psychotic dose is only 1 mg per day. What actually happens when methadone is mixed with alcohol??

: http://alcoholdrugstreatment.info/what-happens-when-you-drink-alcohol-with-methadone