But I don't need Viagra with the housekeeper

Joke:

This man got his prescription for Viagra, and goes home to get
ready for when his wife gets home. He calls her on the phone,
and says, "I'll be home in an hour."

"Perfect," she replies.

The man thinks her agreement is because the Doctor told him
to take his Viagra an hour before. He takes the Viagra and
waits. Well, and hour goes by, the man is ready to go, but no
wife?

She calls him on the phone and she says, "Traffic is terrible. I
won't be there for about an hour and a half."

The man, frustrated, calls his Doctor for advice. "What should I
do?" he asks.

The Doctor replied, "It would be a shame to waste it. Do you
have a housekeeper around?"

"Yes" the man replied.

"Well, maybe you can occupy yourself with her instead?" said
the Doctor.

The man then replied with dismay, "But I don't need Viagra
with the housekeeper..."