This is an oldie, which will probably go straight to the orange room

A woman says to her doctor, "My husband is losing interest in me. What can I do"
The doctor gives her a small bottle of colourless liquid. "Give him half the contents of this in his coffee, but don't just give it to him. Make it a romantic occasion. A candlelit supper with soft music and dim lighting and all the trimmings. O.K.?"
Some time later, he sees the woman and asks, "How did it go?"
She said, "Oh! it was fine! Marvelous in fact. I did what you suggested, romantic dinner, soft lights etc, and as I went to pour the liquid, my hand slipped and I put it all in."
"What happened?"
"Well", she said, "He grabbed me there and thrn and ripped all my clothes off.
We made passiionate love across the dining table. It was wonderful!
But I don't thjnk we'll ever be able to go to that restaurant again..."