How can a patient taking nitroglycerin sublingually for angina determine if their medication has lost strength?

A patient can determine if their sublingual nitroglycerin has lost strength by noticing a lack of tingling sensation when the tablet is placed under the tongue. Nitroglycerin is designed to dissolve quickly, and one of the characteristic effects when it is actively working is the tingling or burning sensation that patients often report. This sensation indicates that the medication is being absorbed properly and is effective in dilating blood vessels to relieve angina symptoms.

If the patient does not feel this tingling sensation, it may suggest that the nitroglycerin has degraded or lost potency, indicating it might not work as intended when needed for acute angina episodes. This method of assessment is particularly useful because it provides an immediate and subjective measure of the medication's effectiveness right at the moment of use.

Other signs, such as the presence of chest pain or dizziness, are not reliable indicators of the nitroglycerin's potency because they may occur for reasons unrelated to the medication's strength. Similarly, changes in color of the tablet are not a consistent or dependable measure of its effectiveness, as the medication can still be effective even if it appears unchanged.