[Tolerance to nitrate derivatives: clinical implications]

With chronic use of organic nitrates, attenuation of their clinical efficacy in angina pectoris and in congestive heart failure can occur. This attenuation is more pronounced if controlled release preparations for oral or transdermal use, leading to continuous high plasma concentrations of the nitrates, are used. Twenty-four hour protection, e.g. in a patient with angina pectoris, is not possible with nitrates, and other substances such as beta-adrenergic blockers and calcium antagonists will often have to be associated. The introduction of "nitrate-free periods" to overcome tolerance is discussed. The use of SH-providing substances such as N-acetylcystein to counteract the development of nitrate tolerance is, at this moment, only experimental.