What is the shelf life of nitroglycerin tablets?

According to a 1974 study, the shelf life of sublingual nitroglycerin tablets is 3 to 5 months¹ once the original bottle is opened. This was at a time when nitroglycerin tablets were supplied in bulk bottles and dispensed in smaller quantities by the pharmacy.

Packaging of nitroglycerin tablets has been changed from 100 tablets to patient convenience packages of 4 bottles of 25 tablets each.

Current storage instructions are: Store at controlled room temperature of 20°–25°C (68°–77°F). Nitroglycerin should be kept in the original glass container and must be tightly capped after each use to prevent loss of tablet potency. There is no official mention of an expiry date after opening.

However, to be safe Drugs.com would still recommend discarding a bottle of nitroglycerin tablets no longer than three months after opening.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1947477/pdf/canmedaj01579-0050.pdf