From the Guidelines
In hypertensive emergencies, nitroglycerin should be overlapped with oral antihypertensives once blood pressure begins to stabilize, typically after 6-12 hours of IV therapy, as recommended by the most recent guidelines 1.
Key Considerations
- The goal is to prevent rebound hypertension and ensure continuous blood pressure control while transitioning from IV to oral therapy.
- Common oral agents used for this purpose include calcium channel blockers, ACE inhibitors, ARBs, or beta-blockers.
- The overlap period typically lasts 2-6 hours, with nitroglycerin dose reduction by 10-20% every 15-30 minutes while monitoring blood pressure.
- It is essential to ensure adequate hydration during this transition and monitor for orthostatic hypotension, which may occur with the combined effects of both medications.
Mechanism of Action
- Nitroglycerin works through vasodilation by increasing nitric oxide.
- Oral agents provide more sustainable control through various mechanisms like blocking calcium channels or inhibiting the renin-angiotensin system.
Clinical Guidelines
- The European Heart Journal's 2019 guidelines on the management of hypertensive emergencies emphasize the importance of close monitoring and treatment with intravenous BP-lowering agents to reach the recommended BP target in the designated time-frame 1.
- The American College of Cardiology/American Heart Association's 2018 guidelines also provide recommendations for the management of hypertensive emergencies, including the use of intravenous antihypertensive drugs and the importance of considering comorbidities and target organ damage 1.
From the FDA Drug Label
INDICATIONS & USAGE Nitroglycerin Injection is indicated for treatment of peri-operative hypertension; for control of congestive heart failure in the setting of acute myocardial infarction; for treatment of angina pectoris in patients who have not responded to sublingual nitroglycerin and β-blockers; and for induction of intraoperative hypotension. The FDA drug label does not answer the question.
From the Research
Overlapping Nitroglycerin with Oral Anti-hypertensives
- In hypertensive emergencies, nitroglycerin can be used as a bridge to intravenous therapy, allowing for rapid blood pressure control while awaiting the preparation of intravenous infusions 2.
- The choice of specific drugs for hypertensive emergencies depends on the underlying causes of the crisis, patient demographics, cardiovascular risk, and comorbidities 3.
- For hypertensive emergencies, a maximum blood pressure reduction of 20-25% within the first hour is considered appropriate, followed by a further gradual decrease over the next 2-6 hours to reach normal blood pressure levels 3.
- Nitroglycerin is preferred when there is acute coronary insufficiency, and a beta-blocker may be added in some patients 4.
- In the case of hypertensive urgencies, a gradual lowering of blood pressure over 24-48 hours with an oral medication is the best approach, and aggressive blood pressure lowering should be avoided 4, 3, 5.
Specific Scenarios
- In patients with acute coronary insufficiency, nitroglycerin is the preferred agent, and it can be overlapped with oral anti-hypertensives once the patient's condition is stabilized 4.
- For patients with hypertensive acute heart failure syndrome, nicardipine may be more effective than nitroglycerin in achieving optimal blood pressure control 6.
- In patients with catecholamine-induced crises, an alpha-blocker such as phentolamine should be given, and labetalol or sodium nitroprusside with beta-blockers are alternatives 4.
Key Considerations
- The efficacy and safety of comparative agents for hypertensive emergencies and urgencies are not well established, and more comparative and randomized trials are needed to provide definitive conclusions 4, 5.
- Agent selection should be based on the perceived need for urgent blood pressure control, the cause of the hypertensive crisis, and concomitant conditions 4, 5.