Authors: Rayna Wallace, Jamie Coates, Kristina Hazard
Background: Blood pressure guidelines involve a stepwise approach with lifestyle modifications and medication(s) to achieve target blood pressure. Calcium channel blockers, amlodipine and nifedipine, are recommended as first-line antihypertensive agents due to their efficacy in lowering blood pressure. While amlodipine and nifedipine’s effects on blood pressure compared to other antihypertensive classes have been well studied, there is limited data regarding nifedipine’s role as a direct substitute for amlodipine. This project aims to evaluate the impact of amlodipine to nifedipine conversions by a remote pharmacy hypertension service to explore the conversion as a potential alternative to intensifying antihypertensive regimens with additional agents.
Methods: This IRB-exempt retrospective cohort project includes Kaiser Permanente Georgia members 18 years or older with a hypertension diagnosis who were enrolled in a remote pharmacy hypertension service and prescribed amlodipine 10 mg or switched from amlodipine 10 mg to nifedipine SR 90 mg between May 4, 2021, and May 3, 2025. The primary objective was to determine if the conversion of amlodipine to nifedipine would improve blood pressure in patients with uncontrolled hypertension as compared to patients remaining on amlodipine. The secondary objective was to assess the average change in blood pressure after the conversion of amlodipine to nifedipine in patients with uncontrolled hypertension. The tertiary objective was to evaluate if the conversion of amlodipine to nifedipine in patients with uncontrolled hypertension could result in ambulatory blood pressure goals being met at the next pharmacy hypertension service visit and within 3 months post conversion. Patients who remained on amlodipine 10 mg were matched up to a 1:2 ratio to patients who were converted to nifedipine SR 90 mg. Conditional logistic regression and generalized estimating equation (GEE) models were applied to report outcomes data.
Results: A total of 664 patients met inclusion criteria, of whom 596 remained on amlodipine 10 mg and 68 were converted to nifedipine SR 90 mg. 63 of the nifedipine SR 90 mg patients were matched to 120 patients remaining on amlodipine 10 mg. Conversion from amlodipine 10 mg to nifedipine SR 90 mg was not associated with statistically significant improvement in blood pressure outcomes. There was no significant difference in systolic blood pressure improvement (OR = 1.23; 95% CI = 0.61, 2.47) or diastolic improvement (OR = 1.54; 95% CI = 0.81, 2.92) between groups. At follow-up, the average systolic blood pressure in the nifedipine group was lower by -2.12; 95% CI = -5.65, 1.42 (p = 0.24) and average diastolic blood pressure was lower by -1.66; 95% CI = -4.36, 1.05 (p = 0.23); neither difference was statistically significant. Similarly, there were no significant differences in change from baseline systolic blood pressure (Estimate: -0.80; 95% CI = -2.72, 1.13) or change from baseline diastolic blood pressure (Estimate: -2.04; 95% CI = -4.59, 0.51) between groups. Achievement of blood pressure goals at follow-up (OR 0.95; 95% CI = 0.43, 2.11) and at 3 months (OR = 0.69; 95% CI = 0.33, 1.45) did not differ significantly between patients converted to nifedipine SR 90 mg and those maintained on amlodipine 10 mg.
Conclusions: Conversion from amlodipine 10 mg to nifedipine SR 90 mg was not associated with significant improvements in blood pressure reduction or goal attainment as compared to those remaining on amlodipine 10 mg after an adjusted analysis. These findings suggest that routine conversion to nifedipine SR 90 mg may not provide additional benefit over continued amlodipine 10 mg therapy. Further assessment of these findings may be warranted in a larger nifedipine cohort.
Contact Rayna Wallace at
[email protected] with any questions regarding this project.
