Background
Despite the worldwide trend towards a wider availability of medicines to the general public without prescription, little is known about their safety when supplied over-the-counter (OTC). Drug safety is dependent on appropriate use (correctly indicated, not contraindicated and no drug interactions) and appropriate dosage. One of the problems of studying OTC medicines is customer recruitment and follow-up.

Method
Prior to a major UK study of OTC medicines, pilot work was done in Grampian using ibuprofen as a model. All users of any tablet or capsule form of ibuprofen (excluding compound products) purchased from the 61 participating community pharmacies, who were aged >18 years and able to give informed consent, were eligible to join the study. Postal questionnaires at one week and two, six and 12 months after the index purchase monitored the follow-up rate, drug usage, past medical history, concurrent medication, symptoms and health service utilisation.

Results
555 customers were recruited. The questionnaire was completed by 433 (81%) of the 544 customers who could be followed-up at one week. The recommended daily dose of OTC ibuprofen (1,200 mg) was exceeded by 35 (8%) customers on at least one day and the prescribed dose (2,400 mg) exceeded on five occasions. During the seven days after the index purchase, ibuprofen was used by 15 customers (4%) with an active or past history of stomach or peptic ulcer, and 30 (7%) with an active or past history of asthma. 38% had purchased ibuprofen for a chronic condition and 32% were still taking it at the end of the initial seven-day period. 28/412 (7%) sought advice during the seven-day period about at least one symptom (range 1-9 symptoms, median 1): 13 (3%) consulted their general practitioner, 12 (3%) a pharmacist, two a GP and a pharmacist, and one a hospital doctor. Eleven consulted about lower abdominal symptoms, nine about gastric symptoms (of these, three consulted about both gastric and lower abdominal symptoms) and a further three about wheeziness. Data from the two, six and 12 month follow-ups will also be presented at the conference.

Conclusions
We have demonstrated that the recruitment of and follow-up of users of OTC ibuprofen is feasible. Although OTC medicines are safe for the vast major of users, adverse events may occur in a small proportion of users. This could still translate into a large number of people affected given the huge number of users of OTC products each year. Pharmacovigilance studies of OTC medicines are needed to quantify this risk and to identify the minority of individuals potentially at risk of adverse events who should avoid these products.