Characteristics and determinants of high volume dispensing in long-term oral nutritional supplement users in primary care: a secondary analysis

BACKGROUND: Oral nutritional supplements (ONS) are recommended for patients who are malnourished or at risk of malnutrition. Appropriate ONS prescribing requires regular monitoring to assess its continued requirement. Previous research identified long-term ONS prescriptions (>6 months) without review, with 70% of these influenced by social factors. AIM: To investigate the characteristics of long-term ONS users in Ireland and the determinants of larger volumes of ONS dispensing. DESIGN & SETTING: Secondary analysis of anonymous dispensed pharmacy claims data of patients dispensed standard ONS for 12 consecutive months in 2018 (n = 912). METHOD: Factors showing significant (P<0.05) univariate associations with above the median consumption of ONS units were entered into a multivariable model. RESULTS: Median age was 76 (range 18 to 101) years, with 66.9% of the sample being ≥65 years. Almost 70% of the samples were on polypharmacy (45.6%; ≥5 medications) or excessive polypharmacy (21.5%; ≥10 medications). Younger age and being on polypharmacy for drugs having an effect on the central nervous system (CNS) were significantly associated with being dispensed more ONS units in univariate and multivariate analysis. Those patients in the age range 18 to 44 were 2.5 fold more likely to be prescribed more ONS units (odds ratio [OR] 2.5; 95% confidence interval [CI] 1.5 to 4.3; P<0.001). Patients using CNS drugs or on CNS polypharmacy were more likely to be prescribed more ONS units (ORs 1.2 and 2.4; 95% CI 0.9 to 1.4 and 1.3 to 4.4 respectively; P = 0.029). CONCLUSION: Older age and polypharmacy characterise long-term ONS users in this study. Younger age and CNS medication polypharmacy are predictors of more ONS units prescribed over a year.