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Hormone replacement therapy: patterns of use studied through British general practice computerized records
M Lawrence1, L Jones, T Lancaster
1University Department of Primary Health Care, Institute of Health Sciences, Headington, Oxford, UK.
Insights
Women who use hormone replacement therapy (HRT) for over a year have a high continuation rate, exceeding 95% annually. However, many long-term HRT users switch formulations, requiring flexibility in treatment protocols.
Area of Science:
- Reproductive Medicine
- Pharmacology
- Epidemiology
Background:
- Hormone replacement therapy (HRT) is commonly prescribed for menopausal symptoms.
- Understanding long-term HRT consumption patterns is crucial for patient management and clinical trial design.
Purpose of the Study:
- To describe the longitudinal pattern of hormone replacement therapy (HRT) consumption in long-term users (>1 year).
Main Methods:
- Longitudinal analysis of prescription data from UK general practices (1991-1995).
- Inclusion of 1224 long-term HRT users and 1154 non-user controls (aged 45-64).
- Data collection via GP records and questionnaires.
Main Results:
- Annual HRT continuation rate for long-term users (>1 year) was over 95%.
- Users of opposed HRT were 50% more likely to discontinue than unopposed HRT users.
- A significant minority of long-term users frequently changed HRT formulations, with three formulations needed for 94% of users over 4 years.
Conclusions:
- High adherence observed once women initiate long-term HRT use.
- Formulation changes are common among long-term HRT users, necessitating adaptable clinical trial protocols.
- Future HRT trials should account for formulation switching in long-term users.
Objective:
We aimed to describe the longitudinal pattern of hormone replacement therapy (HRT) consumption in a cohort of long-term users (defined as use for >1 year).
Method:
We carried out longitudinal analysis of prescription data derived from GPs' computer records. Subjects were recruited through 15 general practices in the former Oxford, South West and North West Thames Regions that contributed to the VAMP/OPCS general practice research database. All women in the practices aged 45-64 years in September 1991 were identified. Of these, the analysis concerned the 1224 long-term users and 1154 non-user controls who remained in the practices from September 1991 to March 1995; 868 (71%) of the users and 698 (61%) of the controls also provided questionnaire data.
Results:
The prevalence of HRT use was 15% in 1992, a rise of 16% from 1991. The prevalence of long-term use was 10%; 22% of the cohort identified as taking HRT between April and September 1991 had left the practices or were not taking HRT 1 year later. But for the group defined as long-term users in 1992, the rate of discontinuation was less than 5% per year over the following 2 1/2 years. Users of opposed therapy were 50% more likely to discontinue than users of unopposed therapy. Almost all women who had or had not undergone hysterectomy were taking unopposed or opposed therapy, respectively. Over 80% of prescriptions were for oral therapy. A third of users of either opposed or unopposed therapy changed the formulation during the 4 years of observation, and two-thirds of those who used both forms changed at least once in addition. Two changes were required to accommodate 94% of users.
Conclusions:
Once women have taken HRT for a year, their continuation rate is over 95% per annum. Although the majority of women stayed with one formulation, a substantial minority changed formulation quite frequently, three formulations being required to accommodate 94% of long-term users over 4 years. Any trial of HRT use will need to recruit long-term users and allow for change in formulation of HRT in its protocol.