Nitroglycerin Spray and Acetylcysteine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Nitroglycerin Spray
Acetylcysteine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Enhanced hypotension and nitroglycerin-induced headache
Interaction Deep Dive
Concurrent administration of nitroglycerin and N-acetylcysteine has been shown to cause significant hypotension and enhance temporal artery dilation23. However, the intravenous combination of nitroglycerin and N-acetylcysteine may also reduce the incidence of an acute myocardial infarction in patients with severe unstable angina pectoris 2. Another study showed that the coadministration of N-acetylcysteine with nitroglycerin had no demonstrable effects on the development of tolerance to the anti-anginal and hemodynamic effects of nitroglycerin, and N-acetylcysteine did not potentiate the vasodilator effects of nitroglycerin 1.
Why it happens (mechanism)
Additive vasodilation
Literature reports
3 reports — tap to read
a) N-acetylcysteine was shown to potentiate the hemodynamic effects of nitroglycerin in a randomized, double-blind study involving 46 patients with severe unstable angina pectoris. The effects of intravenous nitroglycerin were compared to those of intravenous nitroglycerin and intravenous N-acetylcysteine (5 grams every six hours). The 24 patients who received combination therapy had a significantly lower incidence of acute myocardial infarction (n=3) than the 22 patients who received nitroglycerin and placebo (n=10). However, combination therapy with intravenous nitroglycerin and N-acetylcysteine produced symptomatic hypotension frequently 2.
b) The effects of N-acetylcysteine on nitroglycerin-induced headaches were analyzed in eleven healthy volunteers, using a double-blind, randomized, placebo-controlled, crossover design. N-acetylcysteine 100 mg/kg or placebo was diluted and infused intravenously over a period of 15 minutes, followed by a nitroglycerin infusion (0.06 mcg/kg/min) over a 20 minute period. The nitroglycerin infusion was then repeated 120 minutes after the initial infusion. N-acetylcysteine potentiated the nitroglycerin-induced headache and also enhanced the temporal artery dilation when compared to placebo (139% vs 127% of baseline). The radial artery was not affected 3.
c) The effect of chronic oral N-acetylcysteine on the development of nitrate tolerance was investigated in patients with stable angina pectoris treated with daily transdermal nitroglycerin. Eight subjects received nitroglycerin 10 mg transdermally daily and N-acetylcysteine 400 mg three times daily or placebo in a prospective, double-blind, randomized crossover manner for four days, with a washout interval of three days. Heart rate, blood pressure, and treadmill walking time measurements showed the development of tolerance to the anti-anginal and hemodynamic effects of nitroglycerin after four days of treatment, and the coadministration of N-acetylcysteine had no demonstrable effect on this. This study also showed that oral N-acetylcysteine did not potentiate the vasodilator effects of nitroglycerin. The authors postulated that oral N-acetylcysteine may be a less effective donor of sulfhydryl groups than intravenous N-acetylcysteine and that nitroglycerin tolerance may be due to mechanisms other than sulfhydryl group depletion 1.
Common questions
Can I take Nitroglycerin Spray and Acetylcysteine together?
Enhanced hypotension and nitroglycerin-induced headache Always confirm with your pharmacist or prescriber before making any change.
How serious is the Nitroglycerin Spray and Acetylcysteine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Nitroglycerin Spray or Acetylcysteine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (3)
- Hogan JC, Lewis MJ, & Henderson AH: Chronic administration of N-acetylcysteine fails to prevent nitrate tolerance in patients with stable angina pectoris. Br J Clin Pharmacol 1990; 30:573-577. DOI
- Horowitz JD, Henry CA, Syrjanen ML, et al: Nitroglycerine/N-acetylcysteine in the management of unstable angina pectoris. Eur Heart J 1988; 9(suppl A):95-100. PubMed
- Iversen HK: N-acetylcysteine enhances nitroglycerin-induced headache and cranial arterial responses. Clin Pharmacol Ther 1992; 52:125-133. DOI
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