Increasing exposure to drug-drug interactions between 1992 and 2005 in people aged > or = 55 years.
BACKGROUND
Drug-drug interactions (DDIs) are responsible for a variety of adverse reactions, particularly in an elderly population.


OBJECTIVE
To assess the frequency and potential clinical relevance of DDIs in a population aged > or = 55 years.


METHODS
Exposure to DDIs was assessed in 7842 people participating in the Rotterdam Study, a population-based cohort study. These people were followed between 1 January 1992 and 1 July 2005. The DDI list of the Royal Dutch Association for the Advancement of Pharmacy, in which DDIs are categorized by potential clinical relevance and quality of evidence, was used. Simultaneous use of interacting drug combinations was calculated on the basis of drug dispensing data from community pharmacies.


RESULTS
The incidence of a first dispensing of DDIs in the study period was 10.5 per 100 person-years and 2.7 per 100 person-years for potentially life-threatening DDIs. The prevalence of DDIs in people aged > or = 70 years increased from 10.5% in 1992 to 19.2% in 2005. Ten DDIs comprised two-thirds of the total exposure time to DDIs. The prevalence of potentially life-threatening DDIs in people aged > or = 70 years increased from 1.5% to 2.9%. This increase was most likely caused by an increase in use of spironolactone combined with renin-angiotensin-aldosterone system inhibitors.


CONCLUSIONS
A large number of people in the Netherlands aged > or = 55 years are exposed to DDIs and this number has increased sharply between 1992 and 2005. Healthcare professionals should pay special attention to the potential risks of DDIs in these people, particularly if spironolactone is involved.
Becker
Matthijs L
ML
Pharmaco-epidemiology Unit, Department of Epidemiology and Biostatistics, Erasmus MC, Rotterdam, the Netherlands.
Visser
Loes E
LE
van Gelder
Teun
T
Hofman
Albert
A
Stricker
Bruno H Ch
BH
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D004347:Drug Interactions; D064420:Drug-Related Side Effects and Adverse Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D015995:Prevalence; D011446:Prospective Studies; D012084:Renin-Angiotensin System / Q000187:drug effects; D013148:Spironolactone / Q000009:adverse effects; D013997:Time Factors
D013148:Spironolactone