Check the information leaflets for his medication and see if any of them say "do not combine with alcohol".
Find out if he is secretly still drinking.
It is harmful to suddenly cut off either the alcohol or the medication. Seek medical advice how to do this properly.
I am dismayed to see some respondents portay clinical depression as 'being manipulative' or that you should be selfish and walk away. Depressed people DO turn temporary molehills into insurmountable mountains and can easily opt to take the easy way out while not fully rational. Driving someone to suicide, if provable, would be a serious offence.
I suspect he's completely dependent on you. Sleep on it, then talk through exactly how he plans to get by without you. The more he thinks, the more he'll realise it's a bad idea.
If you do decide to walk away, at least get him emotionally stable and on the way to drying out first.