I am trying to remember the name of a short story by Roald Dahl, about a man who systematically got drunk at home every Saturday night. His wife kills him, I think by putting something in his drink.
You are probably looking for Lamb to the Slaughter.
The only difference is that the wife, Mary Maloney, kills her husband, Patrick, by hitting him in the back of the head with the frozen lamb leg, and not by poisoning as you seem to remember.
Mary Maloney is the anti-hero of the story. Despite being a very loyal and kind wife, she is obsessed with her husband Patrick. As a housewife devoted to making a comfortable home for Patrick and pregnant with their first child, she awaits his return home from his job as a police detective. Mary is very content in her marriage and believes her husband to be as well. When he returns, Mary notices he is uncharacteristically aloof and assumes he is tired from work. After having more to drink than usual, Patrick reveals to Mary what is making him act strangely. Although it is not explicitly stated, it is suggested that Patrick has asked for a divorce as he states she "will be looked after."
Seemingly in a trance, Mary fetches a large leg of lamb from the deep-freezer in the cellar to cook for their dinner. Patrick, his back to Mary, angrily calls to her not to make him any dinner, as he is going out. While he is looking out of the window, quite suddenly Mary strikes Patrick in the back of the head with the frozen lamb leg, killing him instantly.