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N-acetyl cysteine* Vitamin C | |
|
N-acetyl cysteine* | |
| Depletion or interference |
None known |
| Side effect reduction/prevention |
None known |
| Reduced drug absorption/bioavailability |
None known |
An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
N-acetyl cysteine
(NAC)
Continuous nitroglycerine use leads to development of nitroglycerine tolerance and loss of
effectiveness. Intravenous (iv) N-acetyl cysteine (NAC), during short-term studies of people
receiving continuous nitroglycerine, was reported to reverse nitroglycerine
tolerance.1 2 In a double-blind study of patients with unstable angina,
transdermal nitroglycerine plus oral NAC (600 mg three times per day) was associated with
fewer failures of medical treatment than placebo, NAC, or nitroglycerine alone. However, when
combined with nitroglycerine use, NAC has led to intolerable headaches.3
4 In two double-blind, randomised trials of angina patients treated with transdermal
nitroglycerine, oral NAC 200 mg or 400 mg three times per day failed to prevent nitroglycerine
tolerance.5 6
Vitamin C
Vitamin C may help maintain the blood vessel dilation response to nitroglycerine. A
double-blind study found that individuals taking 2 grams of vitamin C three times per day did
not tend to develop nitroglycerine tolerance over time compared to those taking
placebo.7 In another controlled clinical trial, similar protection was achieved
with 500 mg three times daily.8
People using long-acting nitroglycerine can avoid tolerance with a ten- to twelve-hour hour nitroglycerine-free period every day. People taking long-acting nitroglycerine should ask their prescribing doctor or pharmacist about preventing nitroglycerine tolerance.
Alcohol
Alcohol, when consumed during nitroglycerine therapy, may cause low blood pressure and
circulatory collapse in extreme cases.9 People using nitroglycerine should avoid
alcohol.
1. Ghio S, de Servi S, Perotti R, et al. Different susceptibility to the development of nitroglycerin tolerance in the arterial and venous circulation in humans—Effects of N-acetylcysteine administration. Circulation 1992;86:798–802.
2. May DC, Popma JJ, Black WH, et al. In vivo induction and reversal of nitroglycerin tolerance in human coronary arteries. N Engl J Med 1987;317:805–9.
3. Iversen HK. N-acetylcysteine enhances nitroglycerin-induced headache and cranial artery response. Clin Pharmacol Ther 1992;52:125–33.
4. Ardissino D, Merlini PA, Savonitto S, et al. Effect of transdermal nitroglycerin or N-acetyl cysteine, or both, in the long-term treatment of unstable angina pectoris. J Am Coll Cardiol 1997;29:941–7.
5. Hogan JC, Lewis MJ, Henderson AH. N-acetylcysteine fails to attenuate haemodynamic tolerance to glycerol trinitrate in healthy volunteers. Br J Clin Pharmacol 1989;28:421–6.
6. 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;30:573–7.
7. Watanabe H, Kakihana M, Sadanori O, Sugishita Y. Randomized, double-blind, placebo-controlled study of the preventive effect of supplemental oral vitamin C on attenuation of development of nitrate tolerance. J Am Coll Cardiol 1998;31:1323–9.
8. Bassenge E, Fink N, Skatchkov M, Fink B. Dietary supplement with vitamin C prevents nitrate tolerance. J Clin Invest 1998;102:67–71.
9. Thelkeld DS, ed. Diuretics and Cardiovasculars, Antianginal Agents, Nitrates. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1992, 143f–4a.
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