Potentially inappropriate prescribing and cost outcomes for older people: a national population study
Authors: Cahir Caitriona , Fahey Tom , Teeling Mary , Teljeur Conor , Feely John , Bennett Kathleen 
Published: January 2010

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Potentially inappropriate prescribing (PIP) refers to medications that should generally be avoided in older populations and doses or frequencies of administrations that should not be exceeded. Studies of PIP have been primarily based on US indicators of appropriateness such as the Beers criteria due to the lack of European specific indicators.

• PIP has not been assessed in full national samples.

• The total cost of PIP drugs and the cost in relation to overall national pharmaceutical expenditure have not been described.

WHAT THIS STUDY ADDS

• One third of the Irish population aged ≥70 years were prescribed at least one potentially inappropriate medication in 2007 based on European criteria.

• There was a signficant association between polypharmacy and the risk of PIP. Polypharmacy was evaluated as the number of different repeat drug classes (≥ three prescription claims) per claimant.

• The most prevalent PIP drugs were: proton pump inhibitors at maximum therapeutic dosage for >8 weeks (40 mg daily omeprazole, pantoprazole and esomeprazole, 30 mg daily lansoprazole and 20 mg daily rabeprazole); non‐steroidal anti‐inflammatories for >3 months; long‐acting benzodiazepines for >1 month and drug duplication within the same therapeutic class.

• The total expenditure on potentially inappropriate drugs was €45 631 319 in 2007 which is 9% of the overall expenditure on pharmaceuticals in those aged ≥70 years in Ireland.

AIMS Optimization of drug prescribing in older populations is a priority due to the significant clinical and economic costs of drug‐related illness. This study aimed to: (i) estimate the prevalence of potentially inappropriate prescribing (PIP) in a national Irish older population using European specific explicit prescribing criteria; (ii) investigate the association between PIP, number of drug classes, gender and age and; (iii) establish the total cost of PIP.

METHODS This was a retrospective national population study (n= 338 801) using the Health Service Executive Primary Care Reimbursement Service (HSE‐PCRS) pharmacy claims database. The HSE‐PCRS uses the WHO Anatomical Therapeutic Chemical (ATC) classification system and details of every drug dispensed and claimants' demographic data are available. Thirty PIP indicators (STOPP) were applied to prescription claims for those ≥70 years in Ireland in 2007. STOPP is a physiological system based screening tool of older persons' potentially inappropriate prescriptions assessing drug–drug and drug–disease interactions, dose and duration.

RESULTS In our study population PIP prevalence was 36% (121 454 claimants). The main contributors to this were: 56 560 (17%) prescribed proton pump inhibitors at maximum therapeutic dose for >8 weeks, 29 691 (9%) prescribed non‐steroidal anti‐inflammatories for >3 months, 17 676 (5%) prescribed long‐acting benzodiazepines for >1 month and 16 201 (5%) prescribed duplicate drugs. The main determinant of PIP was polypharmacy. The likelihood of PIP increased with a significant linear and quadratic trend (P < 0.0001) with the number of drug classes.The maximum net ingredient cost of PIP was estimated to be €38 664 640. Total PIP expenditure was estimated to be €45 631 319, 9% of the overall expenditure on pharmaceuticals in those ≥70 years in 2007.

CONCLUSIONS The findings identify a high prevalence of PIP in Ireland with significant cost consequences.