Conversions from captopril to lisinopril at a dosage ratio of 5:1 result in comparable control of hypertension.

OBJECTIVE

To provide clinical support that conversion from captopril to lisinopril at a daily oral dosage ratio of 5:1 maintains comparable therapeutic efficacy, and to estimate retrospectively cost savings because of conversion from captopril to lisinopril therapy at the study site and with the associated overall drug conversion program instituted by Kaiser Permanente.

DESIGN

An open-label, randomized, prospective, parallel study was performed in 56 patients with mild-to-moderate hypertension. In a 4-week preroandomization period, oral maintenance dosages of captopril were established. Patients then were randomly assigned either to continue taking captopril or to change to lisinopril at an initial conversion ratio of captopril 5 mg to lisinopril 1 mg. Blood pressures were evaluated 2, 4, 8, and 12 weeks postrandomization. If necessary, dosages were adjusted to maintain adequate efficacy (i.e., systolic pressure < 160 mm Hg and diastolic pressure < 90 mm Hg in the prerandomization period; diastolic pressure < 90 mm Hg postrandomization). Cost savings for the study site and to the overall program with respect to conversion from captopril were defined as the difference between the estimated drug costs and the drug costs projected if the conversion had not been made.

SETTING

Woodland Hills Medical Center of the Southern California Region of Kaiser Permanente Medical Care Program.

MAIN OUTCOME MEASURES

The main outcome measures were systolic and diastolic blood pressure. The measure for the retrospective cost savings analysis was estimated cost savings based on the number of prescriptions written for captopril and lisinopril from December 1988 through December 1993, and the average wholesale price.

PARTICIPANTS

Members of the Kaiser Permanente Medical Care Program who were diagnosed with mild-to-moderate hypertension and whose hypertension was controlled by captopril alone. Retrospectively, mild-to-moderate hypertension would have been classified as stages 1-3, based on the current guidelines of the Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure.

RESULTS

The blood pressures of patients in whom captopril therapy was switched to lisinopril therapy were maintained throughout the entire study within the defined acceptable limits of control when the conversion was initiated at a daily oral dosage ratio of 5:1. The final dosage conversion ratio was not significantly different statistically from the theoretical dosage conversion ratio of 5:1.

CONCLUSIONS

The conversion from captopril (in equally divided daily doses) to lisinopril (once daily) at a dosage ratio of 5:1 maintained comparable control of mild-to-moderate hypertension with no increase in adverse effects. In addition, the cost savings associated with an overall drug conversion program were substantial, and the conversion provided a preferred once-daily dosing regimen.