Which statement is true about nitroglycerin?

The statement that nitroglycerin sublingual (SL) tablets must be replaced after 6 months of opening is true because nitroglycerin is sensitive to moisture and light, which can degrade its efficacy over time. Once a bottle is opened, the tablets are exposed to air and humidity, which can lead to decreased potency.

Pharmacists recommend that patients ensure their nitroglycerin is fresh and effective by replacing it periodically, specifically after about 6 months of opening. This rule helps ensure that patients using nitroglycerin for chest pain or angina receive medication that works properly.

The other options are incorrect due to the specific storage and handling requirements of nitroglycerin. It should be stored under controlled temperatures to maintain its efficacy, requires protection from light, and should be dispensed in light-resistant containers to prevent degradation.