By Arjen Peters

THE HAGUE, The Netherlands (Reuters Health) - A large proportion of hospitalisations are the result of avoidable medication errors, a Dutch analysis of 64 studies shows.

The problem is more serious among people older than 65, Hein Beijer and Kees de Blaey of the Scientific Institute of Dutch Pharmacists conclude, based on their investigation of 62 international studies and two Dutch reports.

In these studies, more than 16% of hospitalised people over age 65 were admitted to the hospital as a result of drug side effects, compared with just over 4% of their younger counterparts, according to the report in Dutch Pharmaceutisch Weekblad.

The 64 studies encompass 123,794 hospitalisations, including 7,553 of people older than 65 years of age. In 6,071 cases--1,261 of them in people over 65--the hospitalisations were ascribed to drug side effects.

The studies cover a 35-year period and were carried out in Australia, the United States and Europe. The research includes public hospitals as well as university centres. Variations in time, location and hospital specialisation did not affect the rate of adverse event-related hospitalisations.

None the studies evaluated the impact of certain types of drugs on the frequency of the hospitalisations, the Dutch investigator said.

In 12 of the studies a distinction was made between foreseeable and inevitable medication side effects.

Among the 1,410 hospitalisations in these 12 studies, 407 (or 29%) were ascribed to side effects caused by an error of medication.

There too, the phenomenon seemed particularly significant among elderly individuals. Eighty-eight percent of patients over 65 were admitted to the hospital following avoidable side effects caused by medication errors, compared with 24% of patients younger than 65.

Extrapolated to the Netherlands, where 1.59 million hospitalisations were reported in 1998, the study results mean that of the 527,880 hospitalisations of people over 65 years, 87,430 could be attributed to medication side effects.

Among the 1.06 million hospitalizations of younger patients, an estimated 44,040 would be related to medication side effects.

Of these, 76,940 hospitalisations of people over 65 years (88% of the 87,430) and 10,580 (24% of the 44,040) in the case of people of younger than 65, are linked to a medication error.

"All in all, that means that 87,520 hospitalisations out of 1.59 million--that is 5.5%--are entirely due to medication errors," Beijer said.

"From a financial point of view, this represents average expenditure of about 430 million euros each year," he said.

This expenditure could be avoided--or at least reduced considerably--by a closer monitoring of patients, in particular of old people, when they purchase the drugs, which is the responsibility of pharmacists, the Dutch researcher said.