Bottle Number 43

A new miracle doctor comes to town, who people say could cure anything. John, the local doubting Thomas, decides to prove the doctor a fraud.
He goes to the doctor and says: "Hey, doc. I've lost my sense of taste." The doctor thinks a while, scratches his head and tells John: "What you need is bottle number 43." He brings out a bottle and tells John to taste its content. John does, and immediately spits it out."Yuck, gross!" he yells. "I just restored your sense of taste," says the doctor. John is furious.
A month later, John goes back to the doctor. "Doc," he says, "I can't remember anything!"
The doctor starts thinking again, and John is thrilled. Aha! Got him. The doctor mumbles to John, "What you need is bottle number 43..." Even before he finishes his sentence, John had fled the clinic.