What are the dose comparisons of all ACE inhibitors used in hypertension?
24 May 2007 note: This question is over 2 years old and may differ to any new research.
A similar question to this was answered by the National electronic Library for Medicines in October 2006, and thus we will reproduce their answer in part here:
“Are there any dose equivalents for different angiotensin converting enzyme inhibitors and any evidence based guidelines on how to switch between different drugs in this class?
… This document aims to identify any evidenced based dose equivalents and guidelines on switching between the following commonly used ACEIs: ramipril, lisinopril, perindopril, captopril, enalapril, fosinopril and trandolapril.
The manufacturers of the 7 ACEIs listed above have no data on dose equivalents and advise that a clinical decision has to be made for each patient when deciding what dose to use (2-14). The current NICE Guidelines for Hypertension (15), Chronic Heart Failure (16), Management of Type 2 Diabetes (17) and Prophylaxis Post Myocardial Infarction (18); and the National Service Framework for Coronary Heart Disease (19) all recommend the use of ACEIs. However, no dose equivalents are suggested in these or any of the other guidelines or consensus documents which recommend their use (20-24).
A literature search found limited anecdotal advice in two small studies and one letter.
In one study, the dose conversions in table 1 and 2 were used to switch inpatients from non-formulary to formulary ACEIs (quinalapril and lisinopril) (25). No conversion data was provided for captopril because it is short acting and was considered unsuitable for automatic interchange.
It is not clear how these equivalents were derived and no details are given on the patients involved in the study.
Similar dose equivalents were published in a letter in the South African Medical Journal in 1992 but there is again little evidence to support them (26). The equivalent doses are detailed in table 3.
The equivalent dose for ramipril compared to the other ACEIs is 5mg; this differs from the ramipril dose conversion used in the first study. The author states that studies are needed to better determine dose equivalence
In a study of 56 patients with mild-moderate hypertension stabilised on captopril, 27 patients were switched to lisinopril using a dose conversion factor of 5:1 based on initiation and treatment doses in the Summary of Product Characteristics (SPCs) for the drugs (27). Following conversion, a third of patients needed further dose adjustments and again, the conversion factor should be used with caution.
Based on clinical experience, a consultant physician at the Newcastle upon Tyne Hospitals Foundation Trust, has found the doses in table 4 to be roughly equivalent (28).
Patient response must be monitored closely and the dose adjusted accordingly…” 
Please note the second half of the answer provides recommendations on how to switch patients from one ACE inhibitor to another (to access this information, click on the link given below).
1. National electronic Library for Medicine. Are there any dose equivalents for different angiotensin converting enzyme inhibitors and any evidence based guidelines on how to switch between different drugs in this class? October 2006. (http://www.nelm.nhs.uk/Record%20Viewing/viewRecord.aspx?id=574588). You need to click on the attachment, at the bottom of the page, to access this information.