US spending on drugs in real terms rose just 0.5% to $320 billion, as patients visited their doctors and used prescription medicines less often.

They are the key findings of a report from the IMS Institute for Healthcare Informatics, noting that young people, age 19-25, increased their use of prescription drugs as many for the first time were able to remain on their parents’ health insurance. However patients aged 65 and over reduced their volume of prescriptions.

The number of visits to doctors by older Americans declined 4.7%, while retail prescription usage slipped 1.1% in 2011. Seniors aged 65 and over reduced their use of drugs by 3.1% last year, most notably in the antihypertensive class, while those aged 19-25 increased their use of medicines by 2.0%, notably for attention-deficit hyperactivity disorder treatments and antidepressants. This was the only age group that increased drug utilisation in 2011, IMS states.

The report also notes that nearly one-third of total healthcare spending was concentrated in five therapy areas – cancer, asthma and chronic obstructive pulmonary disease, dyslipidaemia, diabetes and mental health. These areas grew faster than the overall market, helped by new treatments and growing diagnosis.

In 2011, spending for brands launched within the past two years was $12.20 billion, compared with $8.50 billion in the year-earlier period. Spending on generics, which now account for 80% of dispensed prescriptions, increased $5.6 billion in 2011.

The institute's R&D director Michael Kleinrock noted that 2011 was "a remarkable year for the volume of drug breakthroughs that became available to millions of Americans". At the same time, he noted that "some troubling trends that began in 2009 persisted with many patients appearing to ration their medical care".

Mr Kleinrock concluded by saying "the implications of fewer doctor visits and lower drug utilisation on patients’ health have yet to play out and require further study".