Introduction
The World Health Organisation has defined an adverse drug reaction (ADR) as "�a response to a drug which is noxious and unintended, and which occurs at doses normally used in man for prophylaxis, diagnosis, or therapy of disease or for the modification of physiological function". ADRs are known to cause problems both in hospital¹ and general practice settings, contributing to longer stays in a hospital, higher costs of hospitalisation². Whilst patient factors are known to be associated with ADRs³, relationships between patients' desire for information and ADRs have not yet been explored. The aim of this study was to explore the incidence of ADRs, the information requirements of these patients and perceptions of their medicines, and relationships between these factors.

Methods
Standardised interviews were conducted at patients' bedsides on four general medical wards in a London teaching hospital. The incidence of ADRs was assessed using a previously validated scale⁴. Patients were asked questions about their information preferences with a Likert-scale, which explored intrinsic desire for information (IDI)^5,6. A clinical expert validated the identified ADRs. The ADRs, patients' responses and demographic data, were coded and analysed.

Results
In total, 82 patients were interviewed, 80 were eligible for ADR assessment. Females accounted for 54.9% (45/82) and 17.0% of patients (14/82) were from an ethnic background. The mean age of the patients was 57 years, with cardiovascular diseases being the most common reason for admission (29.3%, 24/82). Only about a quarter of the total sample was currently working and around 70.6% of patients (48/68) were or had been lower supervisory, craft and related employees or employees in semi-routine and routine occupations.

Twelve patients (15.0%) had experienced "definite" and "probable" adverse drug reactions during their admission, 26.3% (21/80) if "possible" cases are included. Opioid analgesics were most commonly associated with ADRs, followed by diuretics, antibiotics and anticoagulants. In the group of patients younger than 55 years, number of medicines taken, and duration of disease was associated with experiencing an ADR (Pearson's r = 0.43, p = 0.01; r = 0.38, p = 0.04, respectively).

The internal reliability of the IDI scale was acceptable in this cohort (coefficient alpha = 0.6). The mean score on the IDI-scale was 17.6, (minimum 9, maximum 22). High scores on the IDI scale (indicating patients who wanted more information about their drugs) were associated with an incidence of adverse drug reactions on admission (Pearson's r = 0.27, p = 0.02).

Conclusions
This study shows that there is an association between the occurrence of an ADR and desire for information. Further work is needed to establish whether patients who intrinsically desire more information (high scorers) identify ADRs more readily than those who do not, or whether the experience of an ADR increases a patient's desire for such information. With further validation, the IDI-scale may be used to assist healthcare professionals to identify patients at risk of ADRs and provide appropriate information and services to these patients.

References

1. Leape L., Brennan T., Laird N. et al. The nature of adverse events in hospitalized patients. N Engl J Med 1991; 324(6): 377-84.
2. Classen D., Pestotnik S., Evans R. et al. Adverse drug events in hospitalized patients. JAMA 1997; 277(4): 301-6.
3. Hurwitz N. Predisposing factors in adverse reactions to drugs. BMJ 1969; 1(643): 536-9.
4. Naranjo C., Busto U., Sellers E. et al. A method for estimating the probability of adverse drug reactions. Clin Pharmacol Ther 1981; 30(2): 239-47.
5. Duggan C., Bates I. Development and evaluation of a survey tool to explore patients' perceptions of their prescribed drugs and their need for drug information. Int J Pharm Pract 2000; 8: 42-52.
6. Åström K., Carlsson J., Bates I. et al. Desire for information about drugs: a multi-method study in general medical inpatients, Pharm World Sci 2000; 22(4): 159-64.