title: Copayments for prescription medicines on a public health insurance scheme in Ireland.
abstract: We assessed the impact of the introduction of a €0.50 prescription copayment, and its increase to €1.50, on adherence to essential and less-essential medicines in a publicly insured population in Ireland.
  
  
  
  We used a pre-post longitudinal repeated measures design. We included new users of essential medicines: blood pressure lowering, lipid lowering and oral diabetic agents, thyroid hormone, anti-depressants, and less-essential medicines: non-steroidal anti-inflammatory drugs (NSAIDs), Proton Pump Inhibitors/H2 antagonists (PPIs/H2 ), and anxiolytics/hypnotics. The outcome was change in adherence, measured using Proportion of Days Covered. We used segmented regression with generalised estimating equations to allow for repeated measurements.
  
  
  
  Sample sizes ranged from 7145 (thyroid hormone users) to 136 111 (NSAID users). The €0.50 copayment was associated with reductions in adherence ranging from -2.1%[95% CI, -2.8 to -1.5] (thyroid hormone) to -8.3%[95% CI, -8.7 to -7.9] (anti-depressants) for essential medicines and reductions in adherence of -2%[95% CI, -2.3 to -1.7] (anxiolytics/hypnotics) to -9.5%[95% CI, -9.8 to -9.1] (PPIs/H2 ) for less-essential medicines. The €1.50 copayment generally resulted in smaller reductions in adherence to essential medicines. Anti-depressant medications were the exception with a decrease of -10.0% [95% CI, -10.4 to -9.6] after the copayment increase. Larger decreases in adherence were seen for most less-essential medicines; the largest was for PPIs/H2 at -13.5% [95% CI, -13.9 to -13.2] after the €1.50 copayment.
  
  
  
  Both copayments had a greater impact on adherence to less-essential medicines than essential medicines. The major exception was for anti-depressant medicines. Further research is required to explore heterogeneity across different socio-economic strata and to elicit the impact on clinical outcomes. Copyright © 2015 John Wiley & Sons, Ltd.
authors.affiliation: Department of Epidemiology and Public Health, University College Cork, Cork, Ireland.
authors.forename: Sarah-Jo
authors.initials: SJ
authors.lastname: Sinnott
authors.affiliation: The Centre of Health Policy and Management, Trinity College Dublin, Dublin, Ireland.
authors.forename: Charles
authors.initials: C
authors.lastname: Normand
authors.affiliation: Pharmaceutical Care Research Group, School of Pharmacy, University College Cork, Cork, Ireland.
authors.forename: Stephen
authors.initials: S
authors.lastname: Byrne
authors.affiliation: Centre for Policy Studies, University College Cork, Cork, Ireland.
authors.forename: Noel
authors.initials: N
authors.lastname: Woods
authors.affiliation: School of Dentistry, University of Leeds, West Yorkshire, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Whelton
mesh_terms: D017047:Cost Sharing / Q000191:economics*; D003669:Deductibles and Coinsurance / Q000191:economics; D018954:Drugs, Essential / Q000191:economics*; D006801:Humans; D007356:Insurance, Pharmaceutical Services / Q000191:economics*; D007494:Ireland; D008137:Longitudinal Studies; D055553:Prescription Drugs / Q000191:economics*
chemical_list: D018954:Drugs, Essential; D055553:Prescription Drugs
keywords: adherence; cost-sharing; drug prescriptions; health policy; pharmacoepidemiology