spotting the placebo

A lovely letter in New Scientist (22 Jan 2001, p26):

From Phillip Gething

As part of my training to join a medical research ethics committee, I attended lectures on drug trials. We were told of a trial in which a patient spotted when her drugs had been switched, even though great efforts had been made to make the capsules appear identical. When asked by her GP why she thought the drugs had been changed, the patient replied, "I always put them down the loo. Until recently they always floated, now they always sink."

Fleet, Hampshire, UK

Being able to spot the placebo clearly wasn't the main problem here!