# Hydralazine Use and Risk of Vasculitis

## TL;DR

Hydralazine use is linked to a slightly higher risk of vasculitis compared to ACE or ARB medications, but the risk is very low and likely not clinically significant.

## Contribution

This study provides population-level evidence on the rare risk of vasculitis associated with hydralazine compared to other blood pressure medications.

## Key findings

- Hydralazine use was associated with a 1.19 hazard ratio for vasculitis compared to ACE or ARB use.
- Vasculitis events were rare in both groups, with an absolute risk difference of 0.3 percentage points.
- The association was no longer significant when accounting for the competing risk of death.

## Abstract

What is the risk of vasculitis associated with hydralazine use compared with use of an angiotensin-converting enzyme inhibitor (ACE) or angiotensin receptor blocker (ARB)?

This cohort study of 583 136 adults in Ontario, Canada, found that, when compared with ACE or ARB use, hydralazine was associated with a higher risk of vasculitis during follow-up. However, vasculitis events were rare in both groups.

This study suggests that vasculitis associated with hydralazine is a rare event and use is unlikely to be associated with a clinically meaningful increased risk of vasculitis.

This cohort study of Canadian adults examines whether hydralazine use is associated with a higher risk of vasculitis compared with angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use.

Hydralazine is a selectively used cardiovascular medication with case reports and case series demonstrating an association between the use of hydralazine and antineutrophil cytoplasmic antibody–associated vasculitis.

To assess the risk of vasculitis associated with hydralazine use compared with use of an angiotensin-converting enzyme inhibitor (ACE) or angiotensin receptor blocker (ARB).

This population-based, retrospective cohort study assessed adults 66 years or older from Ontario, Canada, who were newly prescribed hydralazine from January 1, 2008, to December 31, 2021. Data analysis was performed from May to August 2025.

Newly dispensed hydralazine in an outpatient setting.

The main outcome was a diagnosis of vasculitis using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes. Overlap-weighted Cox proportional hazards regression was used to examine the association between hydralazine use (active comparator: ACE or ARB) with new-onset vasculitis.

Of a total of 583 136 eligible adults (mean [SD] age, 73.0 [7.2] years; 51 827 [55.2%] female), 40 748 individuals were dispensed hydralazine and 542 388 an ACE or ARB. Hydralazine use compared with ACE or ARB use was associated with a higher risk of vasculitis during follow-up (hydralazine: 328 events [0.8%]; ACE or ARB: 2712 events [0.5%]; absolute risk difference, 0.3 percentage points; hazard ratio, 1.19; 95% CI, 1.04-1.37). Results were no longer significant when accounting for the competing risk of death.

In this cohort study of adults who were newly prescribed hydralazine, vasculitis associated with hydralazine was rare, despite multiple reported cases. Use of hydralazine is unlikely to be associated with a clinically meaningful increased risk of vasculitis.