Hydralazine and NAT2: Slow and Rapid Acetylation
Two people taking the same dose of hydralazine can have different blood-pressure responses. One reason is how quickly their bodies process the medicine. The NAT2 gene helps explain this difference and can give your prescriber useful information when planning treatment.
How hydralazine works
Hydralazine relaxes blood vessels, making it easier for blood to flow and lowering blood pressure. It is prescribed alone or alongside other blood-pressure medicines. Its effects on circulation can also cause headache, a faster heartbeat, or palpitations. The balance between blood-pressure control and side effects is part of finding a suitable treatment plan. [1]
Why NAT2 changes drug exposure
NAT2 makes an enzyme that converts hydralazine into inactive metabolites through a process called acetylation. Inherited differences in this enzyme influence how much active drug remains in the body. A slow acetylator generally has higher drug levels at the same dose than a rapid acetylator. [2]
Genetics adds an explanation for differences in drug handling; your blood-pressure readings and experience with treatment show how the medicine is working for you.
Understanding your acetylator result
| Result | Meaning |
|---|---|
| Slow acetylator / poor metabolizer | Two decreased-function alleles. Higher exposure can increase both blood-pressure lowering and the risk of adverse effects. |
| Intermediate acetylator | One increased-function and one decreased-function allele. CPIC groups this result with rapid acetylators for hydralazine prescribing. |
| Rapid acetylator | Two increased-function alleles. Lower exposure than slow acetylators can mean a higher dose is needed for the same effect. |
| Indeterminate / unavailable | The report cannot assign a supported result. This does not establish rapid or slow acetylation. |
The metabolizer categories above follow CPIC's NAT2 interpretation. [2]
How the 2025 CPIC guideline helps
CPIC provides oral hydralazine recommendations for adults with resistant hypertension. These address starting treatment, titration, and caution with higher doses in slow acetylators. The guideline found insufficient evidence for specific genotype-based recommendations in heart failure, so that use needs separate clinical consideration. [2]
Monitoring still matters
Hydralazine can occasionally cause a lupus-like illness, including joint symptoms, fever, or persistent malaise. The prescribing information also describes monitoring with blood counts and antinuclear antibody testing during prolonged treatment. Tell your clinician about new symptoms; a genetic result cannot diagnose their cause or replace follow-up. [1]
At an appointment, bring your report, current dose and schedule, recent blood-pressure readings, and medication list. Useful questions include whether your NAT2 result affects the planned titration, which symptoms to report, and when your next blood-pressure or laboratory check is due. Do not change your dose on the basis of the report alone.
Hydralazine in your Gene2Rx report
The v4 Full Report includes hydralazine for consumer DNA tests and whole-genome sequencing. It explains your NAT2 result alongside the relevant prescribing guidance. If your DNA data cannot resolve a result, the report shows that limitation rather than assigning a default metabolizer category.
You can explore the supported variants on the NAT2 gene page, or browse all medications in the report.
Sources and further reading
Genes that affect Hydralazine
See the full list of drugs affected by each gene:
This page explains pharmacogenetic evidence. Clinical decisions depend on your medical history, other medicines, and a qualified clinician's assessment.