“Sexual orgasm relieves pain about the same amount as a dose of morphine”How do they measure it?

I read that in a book about pain relief… but if you are in severe pain do you feel able to have sex?And even if you do,who are you meant to have it with?Is it prescription

This entitles the bearer to ten orgasms a week signed The doctor.

The book did not say if morphine is as good as sex, but I once had some mixture called chalk and opium for gut trouble and it certainly changed the world for a while.It’s illegal now of course unlike sex… is there a message