Why must nitroglycerin be stored in its original container?

Why Nitroglycerin Must Be Stored in Its Original Container

Nitroglycerin must be stored in its original glass container because the drug is highly volatile and will rapidly lose potency through evaporation, adsorption to alternative materials, and degradation from environmental exposure—making it therapeutically ineffective when patients need it most. 1

Primary Mechanisms of Potency Loss

Volatility and Evaporation

• Nitroglycerin is an inherently volatile substance that evaporates readily from tablets if strict storage precautions are not maintained 2
• The FDA drug label explicitly states that nitroglycerin "should be kept in the original glass container and must be tightly capped after each use to prevent loss of tablet potency" 1
• Tablets transferred to pill boxes or alternative containers deteriorate within one week and become therapeutically unreliable 2

Material Adsorption Issues

• Plastic containers cause significant drug loss through adsorption—studies show 55% potency loss at room temperature and 30% loss even when refrigerated after just seven days in plastic bags 3
• Cotton, paper, or other materials stuffed into bottles accelerate potency loss considerably 2
• The original glass container is specifically designed to minimize these adsorption and permeation issues 1

Environmental Factors Affecting Stability

Temperature and Humidity

• High temperature storage results in the most rapid loss of potency, with tablets carried in pant pockets (body temperature exposure) losing potency faster than those in purses 4
• The FDA specifies storage at 20°-25°C (68°-77°F) in controlled room temperature conditions 1
• Proper storage away from extremes of temperature and direct sunlight is essential to protect the drug from degradation 5

Headspace and Container Size

• Potency is directly dependent on the headspace (air volume) in the bottle—larger bottles with fewer tablets have more air exposure and faster degradation 4
• A 100-count bottle carried in a pant pocket falls below acceptable potency limits at 12 months, while a 25-count bottle maintains potency for 2 years under the same conditions 4
• Frequent opening of containers reduces potency considerably by introducing moisture and oxygen 2

Practical Storage Timeline

Optimal Storage Conditions

• Tablets kept in small, amber, tightly capped glass bottles in a refrigerator maintain potency for 3-5 months when opened once weekly 2
• After 5 months, unused tablets should be discarded even under optimal storage 2
• Contemporary formulations stored in original bottles in temperate environments can maintain potency for more than 2 years when carried in a purse 4

Compromised Storage

• Tablets in pill boxes or alternative containers deteriorate within 7 days and must be discarded 2
• Medication cups or strip packaging may preserve potency for 7 days only with specific stabilized formulations, but this requires FDA clearance 6

Critical Clinical Implications

Patient Safety Concerns

• Degradation may occur without visible discoloration or precipitation, meaning patients cannot visually assess potency 5
• The American College of Cardiology emphasizes that patient education should include proper storage and administration of sublingual tablets 7
• Using degraded nitroglycerin during an acute coronary event could result in treatment failure and adverse outcomes including myocardial infarction or death 5

Common Pitfalls to Avoid

• Never transfer tablets to pill organizers or alternative containers for convenience—this guarantees rapid potency loss 2
• Never remove cotton or stuffing from the original bottle if present, as manufacturers include this for specific stabilization purposes 2
• Never store in bathrooms or cars where temperature and humidity fluctuate dramatically 4
• Always check expiration dates and renew prescriptions promptly, as degradation accelerates over time 5

Patient Counseling Points

• Keep the bottle tightly capped immediately after each use—every opening introduces air and moisture 1
• Carry the smallest bottle size practical to minimize headspace and extend usable life 4
• Store in a cool, dry location away from body heat (avoid pant pockets when possible) 4
• Replace tablets every 3-6 months regardless of expiration date if frequently opened or exposed to suboptimal conditions 2
• The burning or tingling sensation under the tongue is NOT a reliable indicator of potency—chemical testing is required 1