Long term follow-up studies of users of nonprescription medicines purchased from community pharmacies: some methodological issues.
BACKGROUND
Despite the wider availability of medicines to the general public, little is known about their safety when supplied without prescription. Pilot work has already tested 4 methods of recruiting users of ibuprofen purchased from community pharmacies. This paper describes the piloting of a fifth method (a shortened questionnaire), long term follow-up rates of all methods, consistency of reporting of ibuprofen use, and issues relating to possible comparison groups in pharmacovigilance studies.


METHODS
A shortened version of a previously tested recruitment questionnaire was used. Eligible study participants were all users, aged over 17 years, purchasing ibuprofen from a research network of community pharmacies (n = 61) in Grampian, Scotland. Postal questionnaires were sent at I week and 2, 6 and 12 months irrespective of the method of recruitment. The follow-up questionnaires collected information about ibuprofen and other drug usage, symptoms and associated health service utilisation.


RESULTS
The shortened form recruited 67% of people issued with a questionnaire. The overall 12-month follow-up rate was 67%, although there were important differences in the rates by method of recruitment. There was reasonable consistency in the reporting of use or non-use of ibuprofen at different follow-up times. In the 12 months after the index purchase, 17% of participants never used any ibuprofen (non-users) and 28% used it for more than 8 weeks in total (long term users). At 12 months, long term users were significantly more likely than short term users (< or =8 weeks total use) or non-users to have experienced dizziness, skin rash, itchy skin and wheeziness in the previous week.


CONCLUSIONS
Our pilot work has confirmed the feasibility of recruiting, and following-up over prolonged periods, users of nonprescription medicines. Evidence of long term use of ibuprofen confirms the need for pharmacovigilance studies of this drug, although further work is required to identify a suitable comparison group in order to inform the interpretation of such investigations.
Sinclair
H K
HK
Department of General Practice and Primary Care, University of Aberdeen, Scotland. h.sinclair@abdn.ac.uk
Bond
C M
CM
Hannaford
P C
PC
D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage* / Q000009:adverse effects; D005500:Follow-Up Studies; D006801:Humans; D007052:Ibuprofen / Q000008:administration & dosage* / Q000009:adverse effects; D004366:Nonprescription Drugs / Q000008:administration & dosage* / Q000009:adverse effects; D010594:Pharmacies / Q000706:statistics & numerical data*; D010865:Pilot Projects; D012606:Scotland; D011795:Surveys and Questionnaires
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004366:Nonprescription Drugs; D007052:Ibuprofen