Are Frozen Medications Okay To Use?

In our latest question and answer, the pharmacist discusses whether or not it is safe to use medications that have been accidentally frozen.

Dec 31, 2017

kricky517 asked

I take buproprion and I filled it recently. I accidentally left it overnight in a freezing car. Is the medication still ok to take?


Storage requirements for medications are important to follow. Improper storage of medication products, or failure to follow appropriate storage recommendations, can cause a variety of problems, potentially resulting in a loss of potency and ineffectiveness of the medication.

While the dangers of storing medication in environments that are too hot are well known (e.g. drug degradation, melting etc...), there is less information available on how low temperatures could potentially affect medication.

How Cold/Freezing Temperatures Affect Liquid Products

We know certain products, most commonly liquids, "biologics" (e.g. Enbrel), insulin products and vaccines are negatively affected if they become frozen.

With insulin products, studies have shown that when frozen and thawed, there is definitive evidence of drug degradation. Frozen insulin products show "particle clumping" and crystal damage. This could possibly lessen the absorption and effectiveness of the medication. Another study concluded that certain insulin products will nearly always degrade if they are frozen.

In regard to vaccines, the World Health Organization warns of the dangers of frozen vaccines. Studies show that frozen vaccines can result in a loss of potency which cannot be restored. Not only can effectiveness be lessened, the risk of side effects, such as abscesses after injection, have been reported. The World Health Organization has specifically listed these vaccines as being ones known to be damaged if frozen:

  • Diphtheria
  • Hepatitis A
  • Hepatitis B
  • Influzena
  • Pertussis
  • Tetanus

Lastly, many new medications are recombinant proteins, which have shown to be extremely likely to degrade if frozen. The freezing and thawing process exerts powerful "shear" and "tension" forces on sensitive proteins, potentially damaging and destroying them.

How Cold/Freezing Temperatures Affect Solid Dosage Forms
How low temperatures can affect solid dosage forms such as tablets and capsules isn't well studied. It could reasonably be assumed that solid dosage forms are less susceptible to degradation from freezing than liquid dosage forms, but again, there isn't much data to confirm this.

Studies on solid dosage form medications indicate that the actual dosage form (e.g. a tablet) is more likely to be affected that the medication. Tablets, capsules and soft gels all contain trace amounts of moisture. The freezing of these products could cause the breakdown or degradation of the dosage form, potentially leading to a loss of actual medication resulting from this breakdown.

There may be some drug or molecular breakdown when solid dosage form medications are frozen, but there isn't a definitive list of drugs which are known to be specifically affected.

The main concerning issue in regard to frozen medications is that we simply don't know which ones are likely to be affected, how they could be affected and to what extent. Drug companies/manufactures do stability tests on their products at a certain temperature range. Most do not study the affect of cold temperature excursions on the product.

In other words, the acceptable temperature range is known for a specific medication when it comes to stability. What is unknown, is how excursions from the accepted temperature range will affect the drug product.

Most medication may be perfectly fine when frozen, but we just don't know. It is extremely important to be confident in the consistent potency and purity of your medication. When they are stored outside of the required storage conditions, ambiguity sets in. For this reason, if your medication has seen extreme temperature excursions, it is recommended to get a replacement product to ensure an intact product.

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