title: How many antibiotic prescriptions are unsubsidised in New Zealand?
abstract: OBJECTIVE
  To determine the proportion of prescriptions for antibiotics which were unsubsidised, in one town in one year, and to use this to develop a model which could be used to estimate the number of unsubsidised prescriptions.
  
  
  METHODS
  Data on all prescriptions for antibiotics during 2002 were extracted from pharmacy computers in one town. Data were obtained from PharmHouse database on all subsidised prescriptions from the town pharmacies during 2002. (The PharmHouse database is a subset of the New Zealand Health Information System database and contains records of all the claims for medicines dispensed within New Zealand.) These were compared and the proportion of unsubsidised prescriptions for each antibiotic calculated. Weighted linear regression was used to develop a model of the relationship between the percentage of each drug subsidised, and patient and prescription characteristics obtainable in PharmHouse.
  
  
  RESULTS
  64.4% of antibiotic dispensings in the study town were subsidised, and therefore captured by the PharmHouse database. The proportion varied substantially between different antibiotics. For particular drugs, the proportion of drugs unsubsidised could be predicted by the price of the drug, the number of days it was prescribed for, and the number of patients aged under six who received subsidised prescriptions.
  
  
  CONCLUSIONS
  Previous studies using PharmHouse data are likely to have significantly underestimated the extent of drug use. Further research is needed on whether this model can help to estimate the extent of unsubsidised prescriptions.
authors: School of Pharmacy, University of Otago, Dunedin. pauline.norris@stonebow.otago.ac.nz
authors: Pauline
authors: P
authors: Norris
authors: Silvia
authors: S
authors: Funke
authors: Gordon
authors: G
authors: Becket
authors: Denise
authors: D
authors: Ecke
authors: Lillian
authors: L
authors: Reiter
authors: Peter
authors: P
authors: Herbison