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OR-31: Longitudinal analyis of antihypertensive drug interactions
Abstract   Open access   Peer reviewed

OR-31: Longitudinal analyis of antihypertensive drug interactions

Barry L Carter, Brian C Lund, Elizabeth A Chrischilles and Nobumasa Hayase
American journal of hypertension, Vol.16(S1), pp.13A-13A
05/2003
DOI: 10.1016/S0895-7061(03)00115-8
url
https://doi.org/10.1016/S0895-7061(03)00115-8View
Published (Version of record) Open Access

Abstract

We previously found a high prevalence of significant antihypertensive drug-drug interactions (ADIs) (23-48% depending on age and number of drugs in the regimen) in 1574 Medicaid patients. The objective of the present study was to determine the change in potentially significant DIs over time among individuals eligible for the Iowa Medicaid Pharmaceutical Case Management (PCM) program. Subjects in this analysis were eligible for PCM, took four or more medications, had one of several chronic conditions and received an antihypertensive drug (AD) at both baseline and 9 month follow-up. ADIs were identified by constructing all pair-wise combinations of a subject's active ADs with all other active drugs and comparing these pairs with a reference source listing DIs. The number of ADIs at baseline was compared with the number in the follow-up drug list. The primary dichotomous outcome variable for logistic regression analysis was whether patients had an increase in the number of ADIs classified as being clinically significant, during the follow-up period, as assessed by a computerized DI screening algorithm. Age, sex, number of medications and whether the subject received PCM services were independent variables in the multiple logistic regression analyses. There were 1377 patients who were still taking an antihypertensive at 9-month follow-up and 373 (27%) received PCM services. Older age (p=0.0003), number of ADs at baseline (p=0.012) and more non-ADs at baseline (p<0.0001) were associated with greater numbers of ADIs of any significance level at 9 month follow-up. Controlling for age and number of drugs, there was no increase in the number of either highly significant ADIs (p = 0.13) or ADIs of any significance level (p=0.71) between those who received versus those who did not receive PCM services. There is a high number of potentially clinically significant ADIs that did not change over 9 months even with increased communication between the pharmacist and physician suggesting either: 1) DIs are well managed by pharmacists and physicians and do not require changes, 2) the majority of DIs are not clinically relevant even though listed in a DI compendium, or 3) there are so many DIs that pharmacists and physicians ignore them and do not make changes in therapy. Further exploration is required to determine if this high frequency of potential drug interactions is clinically relevant in this population.
antihypertensives Drug interactions

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