It is not a cure for racism - but researches have discovered that a commonly prescribed heart drug alters subconscious racial attitudes.

Tests on volunteers after taking the drug showed they were less racially biased than those who took a placebo.

The finding suggests the effects of medicinal drugs taken by millions should be taken into account when considering racial attitudes.

Professor Julian Savulescu of Oxford University's Faculty of Philosophy, a co-author of the study, said: “Such research raises the tantalising possibility that our unconscious racial attitudes could be modulated by using drugs, a possibility that requires careful ethical analysis.”

The researchers say racism is founded on fear and the heart drug used in the study, propranolol, helps damp down fear by blocking nerve circuits that govern the heart rate and the part of the brain linked with emotional responses.

“Biological research aiming to make people morally better has a dark history. Propranolol is not a pill to cure racism. But given that many people are already using drugs like propranolol which have 'moral' side effects, we at least need to better understand what these effects are,” Professor Savulescu said.

The small study, published in Psychopharmacology, involved 18 people given propanolol whose responses to a series of questions were compared with those from 18 given a placebo.

In the first “explicit prejudice” test they were asked to rate how “warm” they felt towards various groups including blacks, muslims, christians, homosexuals and drug addicts. There was no difference between those who took the drug and those who took the placebo.

In the second “implicit association” test, they were shown black and white faces and asked to sort them as quickly as possible to positive and negative categories. The findings showed the drug abolished implicit racial bias.

Sylvia Terbeck, lead author and experimental psychologist at Oxford University, said: “Implicit racial bias can occur even in people with a sincere belief in equality. Many people with medical conditions are probably already on drugs which affect subconscious bias. More research is needed into how drugs which affect our nervous system affect our moral attitudes and practices.”

Chris Chambers, Senior Research Fellow at the School of Psychology, Cardiff University, said the finding was “remarkable” but should be viewed with “extreme caution”.

The effects could have been due not to the drug changing racial attitudes, but because it reduced heart rates or altered brain systems more generally.