"Confusing" instructions on medicine bottles and packs dispensed by UK pharmacies are to be replaced with simpler words and phrases, starting from  this month.

Around two million prescriptions are issued every day in the UK, and the law requires each bottle or pack of medicines which is dispensed to have a printed label explaining how the medicine should be taken. However, many commonly-used phrases on medicine labels are easily misunderstood, causing patients to behave in ways which compromise the safety and effectiveness of their treatment, according to work done by researchers at the University of Leeds in collaboration with the Leeds-based company Luto Research.

"It is vital that wordings on labels are simple and straightforward," said Theo Raynor, professor of pharmacy at Leeds University. "Most medicines do contain leaflets providing detailed information for patients, but these leaflets can get lost or overlooked. Patients' behaviour tends to be guided by the instructions on the outside of medicine bottles and packets of pills, so these must be as clear and unambiguous as possible," he added.

Prof Raynor and colleagues tested a selection of instructions on a large number of volunteers aged 20-80, rewording any phrases that people found confusing and then checked that their suggested revisions were easier to understand with more volunteers.

One example of a word which the researchers found was not always readily understood is "drowsiness."  Comprehension is improved by using the phrase: "this medicine may make you feel sleepy" instead, they say.

Another good example is the wording "avoid alcoholic drinks," noted Prof Raynor. "Our user tests have shown that the word 'avoid' can cause confusion and that some people think it only means they should limit their alcohol intake. This phrase will now be replaced by the instruction: 'do not drink alcohol while taking this medicine,' which is far clearer," he said.

The revised phrases have been included in the latest version of the British National Formulary (BNF), which commissioned the research, and the software used by large pharmacy chains and independent pharmacists to print instruction labels is updated regularly, "so we would expect to see these new phrases appear within the next six months," said Prof Raynor.