What does a fizzing sensation under the tongue when using sublingual nitroglycerin indicate?

A fizzing sensation under the tongue when using sublingual nitroglycerin indicates that the medication is potent and active. This formulation is designed to dissolve quickly under the tongue, allowing the nitroglycerin to enter the bloodstream rapidly and provide relief from angina symptoms. The fizzing sensation is often a result of the carbonation process that occurs as the medication interacts with saliva, which is an intended effect of the drug's formulation.

When this sensation is felt, it signals to the user that the sublingual nitroglycerin is functioning as intended and is effective for treating angina. Proper potency and effectiveness are crucial for the immediate relief of angina attacks, making this sensation a positive sign of drug efficacy.