Using computers to test medicines could soon become routine, after the introduction of European Union regulations that require stricter testing for drugs intended for children.

Computer models that simulate the action of a drug on the body could hasten the development of new medicines and prevent children or adults being involved in unnecessary clinical trials - although they cannot completely substitute for tests in humans, researchers say.

Up to three quarters of medicines prescribed for the under18s have never been tested on children, leaving medics to rely on their best judgment to decide what drugs and dosages to give. This can cause child patients to be given inappropriate or ineffective doses. In nearly one in ten cases, children being treated in hospital suffer an adverse drug reaction. In some cases this can be fatal.

Under European regulations that come into force this week, if a drug has any application for use in children, it now has to have some data to support this use before it will be licensed. This will require extra testing by drug companies.

A British company says that computers can now be used to predict with accuracy the correct dosage, absorption and possible side-effects of new drugs in children. Simcyp Ltd, based in Sheffield, is announcing today a version of a paediatric simulator that will allow companies and doctors to test the effects of drugs on “virtual” children before they are given to patients.

Amin Rostami, Professor of Systems Pharmacology at the University of Sheffield and director of research and development at Simcyp, said that computers were now able to replicate the interaction with the body of substances and doses, based on initial laboratory studies.

Children were unable to consent to volunteer for clinical trials and parents unwilling to put them forward unless they could be assured of safety, he said, but “we now have a tool which allows complex clinical scenarios to be explored in the safety of a computer”.

Dr Rostami added: “Modelling and simulation can negate the need for some ‘real-life’ studies, circumventing ethical and practical issues that arise when pharmaceutical companies conduct clinical trials in young subjects.

“Many changes occur during development of a new drug which affect the way that the body handles medicines. In particular, children under two years old are the most physiologically different to adults, so it can be too simplistic to scale back from adult values when determining appropriate doses for children, as currently happens.”

Using the software could cut by up to two years the time needed to develop new drug, he said.

“Virtual trials cannot replace the hard evidence of giving drugs to patients to find out their clinical effects, but could be crucial when designing studies which impact on rare genotypes or in identifying individuals, such as children, who are at extreme risk from adverse reaction,” he said.

Simcyp’s clients already include nine out of ten of the world’s biggest drug companies, such as Pfizer, Astra-Zeneca, Eli Lilly and Novo Nordisk.

Other companies in America and Israel are already using computers to simulate the action of compounds on solid cancer tumours and sarcomas, as well as diseases such as asthma, rheumatoid arthritis and diabetes.

In view of the extra work now needed to produce medicines for use in children, the EU regulations suggest that companies will be able to retain patents and intellectual property rights over new paediatric drugs for six months longer than the seven to twelve years that has previously been the case.

George Rylance, a paediatrician at the Royal Victoria Infirmary, Newcastle, who helps to produce the British National Formulary for Children, said that dosages must be tailored for each child, calculated by weight and age.