From the Guidelines
Hydralazine can cause a rash due to drug-induced lupus-like syndrome, particularly at higher doses. The rash is a result of an immune-mediated reaction where hydralazine acts as a hapten, binding to proteins in the body and triggering an immune response 1. This reaction can occur in approximately 5-10% of patients taking the medication and is usually mild to moderate in severity. Some key points to consider include:
- The mechanism involves an immune-mediated reaction where hydralazine acts as a hapten, binding to proteins in the body and triggering an immune response.
- Patients who are slow acetylators (a genetic variation affecting drug metabolism) are at higher risk for developing these reactions.
- If a patient develops a rash while taking hydralazine, they should contact their healthcare provider immediately, as in some cases the rash may be part of a more serious reaction called drug-induced lupus erythematosus, which can occur with long-term hydralazine use, particularly at higher doses (above 100 mg daily) 1. Management typically involves discontinuation of the medication and switching to an alternative antihypertensive agent, along with symptomatic treatment of the rash with antihistamines or topical corticosteroids if needed. It is essential to monitor patients taking hydralazine for signs of a rash or other adverse reactions and to adjust the treatment plan accordingly to minimize the risk of morbidity, mortality, and to improve the quality of life.
From the FDA Drug Label
WARNINGS In a few patients hydrALAZINE may produce a clinical picture simulating systemic lupus erythematosus including glomerulonephritis. The cause of a rash in patients taking hydralazine is likely related to a systemic lupus erythematosus-like reaction, which may occur in a few patients taking this medication 2.
- The rash is a symptom of this reaction, which can also include glomerulonephritis.
- It is recommended to discontinue hydralazine unless the benefit-to-risk determination requires continued antihypertensive therapy with this drug.
From the Research
Causes of Hydralazine-Induced Rash
- Hydralazine, an antihypertensive medication, has been associated with various side effects, including autoimmune diseases such as hydralazine-induced antineutrophil cytoplasmic antibody-associated vasculitis (ANCA-vasculitis) and lupus-like syndrome, which can manifest as a skin rash 3.
- The skin symptoms caused by hydralazine are not unique to this drug, but certain symptoms, such as lupus erythematosus-like eruptions, eczema, or urticaria, have been reported 4.
- A case study reported a patient who developed toxic epidermal necrolysis (TEN) after taking hydralazine, highlighting the potential for severe allergic reactions, particularly in patients with renal failure 5.
- Another study found that patients who developed hydralazine-induced lupus often had skin involvement, along with cardiopulmonary and renal involvement, and were positive for antinuclear antibody (ANA) and anti-histone antibody 6.
- The development of a rash in patients taking hydralazine may be a sign of an underlying autoimmune reaction, and discontinuation of the medication, along with immunosuppressive treatment, may be necessary to manage the condition 3, 7.
Risk Factors and Diagnosis
- Patients who have been exposed to hydralazine for more than 12 months may be at higher risk of developing hydralazine-induced lupus and associated skin symptoms 6.
- A diagnosis of hydralazine-induced vasculitis or lupus-like syndrome can be difficult to make, and a high index of suspicion is necessary, particularly in patients who present with vague symptoms such as fatigue, weight loss, and anemia 7.
- Laboratory tests, such as ANA, anti-histone antibody, and anti-myeloperoxidase (MPO) antibody, may be helpful in diagnosing hydralazine-induced lupus and predicting the severity of the condition 6.