Could you make it a novel?

I'd run it as a parody of Chinatown, but set in the 1970s, with the wife hiring a Jake-like P.I.  who then moves the plot and enhances your single theme encounter. THe main theme would be the ascendency of the mega-profit pharmaceutical industry, the death/disability of thousands by experimental or supposedly proven drugs foisted on a naive populace. The antagonist would be the pharmaceutical companies super secret agents or agent, who are part of a broader conspiracy to get full strength cyanide (Called by its medical name: Sighasnide, and marketed as a tick or leech remover) for death of an unfaithful spouse, or for other marital problems, into the market place, etc.

Tongue-in-cheek writing might allow story arc to ascend, but the conspiracy would have to be foiled in the end by the Jake like character. I'd think the wife deserves a negative fate at the end of story to discourage actual readers from poisoning their husbands.

I can see the product, Sighasnide, packaged especially for women, as women use poison for murder more often. But of course a men's version would also need to be made available... BitchOff! This would be a cyanide product created to keep in-heat female dogs away from male dogs... and would be sold over the counter without a prescription. And those in-the-know (and how to use it) would use it as a murder poison.