When you are drunk, then you are not in your senses and doing gambling at that time is too much risky. I do not say that you will lose more if you are drunk. The reason is that gambling is based upon luck so even if you are half asleep or not in full conscious , you may still win because of the luck factor but things do not end there.
When your mind is not fully devoted to gambling, you will not know how much to bet or gamble. The emotions will be all over you and there will be no money management as risk management requires full attention of mind and a person who is drunk is unable to know the good and bad for himself at that moment.
You are right, In my point of view I think taking drugs is not a good sign of that person, and gambling while intoxicated is a completely waste of money. We always suggest to people that you invest the amount of money that you can afford to lose for gambling, but I think we should add something more here, gambling should be done only when a person's mental state is normal. Gambling should never be done in situations where people cannot control themselves, be it drunk or tired.