How to Store Mercaptopurine Tablets in the Scorching Summer?

How to Store Mercaptopurine Tablets in the Scorching Summer?

Mercaptopurine, commonly known as 6-mercaptopurine, is a cornerstone medication for treating childhood acute lymphoblastic leukemia. It remains essential throughout the entire treatment process and is a staple in homes with children suffering from this condition. As summer arrives, how should mercaptopurine tablets be stored in a hot and humid environment to ensure their efficacy is not compromised?

Quick Summary:

1. Store mercaptopurine tablets at a temperature between 10-30°C, avoiding direct sunlight.

2. Do not keep mercaptopurine tablets in the refrigerator. If the room temperature exceeds the storage range, consider placing them in an air-conditioned room.

3. During the humid summer months, store mercaptopurine tablets in their original packaging inside a separate airtight container, kept in a dry place such as a bedroom or living room, ensuring the humidity is around 35%-75%.

4. After opening, tightly close the bottle of mercaptopurine tablets. The usage period should not exceed six months or 25% of the remaining shelf life (whichever is shorter).

5. Inspect the tablets for any discoloration, mold, or softening. If any changes are observed, discontinue use.

What Factors Can Cause Mercaptopurine Tablets to Deteriorate?

Firstly, it's important to understand that many factors can affect the storage quality of mercaptopurine tablets. The most significant factors include prolonged exposure to air, strong light, high temperature, high humidity, and damage from microorganisms and insects. Oxygen and carbon dioxide in the air can cause oxidation of the medication, while light acts as a catalyst for chemical reactions such as oxidation and decomposition. High temperature and humidity can also accelerate the degradation of the medication. Therefore, household medications must be stored properly.

Should Mercaptopurine Tablets Be Stored in the Refrigerator During Summer?

Before answering this question, let's take a look at the storage instructions on the mercaptopurine tablet packaging: protect from light and store in a sealed container. The 2020 edition of the Chinese Pharmacopoeia also specifies that mercaptopurine tablets should be stored in a light-protected, sealed manner. Furthermore, the pharmacopoeia indicates that if no specific storage temperature is mentioned, it generally refers to room temperature, which is 10-30°C. Therefore, the storage conditions for mercaptopurine tablets should maintain a temperature between 10-30°C, avoiding direct sunlight to prevent deterioration, moisture absorption, volatilization, or contamination from foreign substances. In principle, they should be stored in their original packaging.

This means that mercaptopurine tablets should not be kept in the refrigerator. Medications are not food; putting them in the fridge does not necessarily prolong their shelf life. Mercaptopurine tablets should be stored according to the instructions before and after opening.

In fact, when it comes to temperature control for medications, extreme measures are not advisable. The temperature in a refrigerator generally ranges from 2-8°C, which does not meet the storage temperature requirements for all medications. Additionally, the high humidity inside a refrigerator can easily cause the tablets to absorb moisture, leading to clumping or mold growth, which can affect the efficacy of the medication. During the summer, when indoor temperatures are high, mercaptopurine tablets can be stored in a cool, well-ventilated place at home, avoiding direct sunlight, such as near windows or on balconies. If the temperature exceeds the required storage conditions, take prompt cooling measures, such as placing them in an air-conditioned room.

On the other hand, summer brings frequent rain and high humidity, so it's also essential to take precautions against moisture for mercaptopurine tablets stored indoors. Generally, a humidity level of around 35%-75% is suitable for storing medications. In the humid southern summer, mercaptopurine tablets can be placed in their original packaging inside a separate airtight container and stored in a dry location like a bedroom or living room. It's crucial to avoid keeping medications in high-humidity environments, such as kitchens or bathrooms, and not to store them near moisture-producing items like fish tanks, humidifiers, or potted plants. After opening the bottle, promptly remove any cotton or paper from inside the bottle to prevent it from continuously absorbing moisture from the air, which can spoil the medication. In areas with excessive humidity, consider placing the mercaptopurine bottle in a moisture-proof box equipped with a hygrometer and desiccant.

Can Mercaptopurine Tablets Be Used Until the Expiration Date Printed on the Bottle After Opening?

After opening, mercaptopurine tablets should still be stored according to the instructions, but the usage period will change. For multi-dose bottles of mercaptopurine tablets, repeated opening and closing during the usage period increases the risk of contamination and physical-chemical degradation, making it unsuitable to adhere to the expiration date specified in the instructions.

Currently, for bottled multi-dose tablets and capsules after the first opening, the "usage period" can refer to the FDA's guidance on "Expiration Dating of Unit-Dose Repackaged Solid Oral Dosage Form Drug Products" (2020): the repackaged medication should be used within six months from the date of repackaging or 25% of the remaining shelf life (the expiration date on the bottle minus the time since opening, multiplied by 25%), using the earlier of the two as the cutoff.

For example, consider a bottle of mercaptopurine tablets that expires in March 2025. If it was opened in November 2022, the remaining shelf life is 28 months, and multiplied by 25% gives us 7 months. Following the guideline of using the earlier expiration date, this bottle should not be used beyond 6 months, meaning it should be discarded by the end of July 2023. If it was opened in early May 2024, the remaining shelf life would be 10 months, and 25% of that is 2.5 months, indicating it should be used by mid-July 2024.

Sometimes, mercaptopurine tablets need to be split for consumption. The stability of broken tablets significantly decreases, and it is recommended to avoid storing the remaining broken tablets for more than 24 hours. Always check the appearance of the tablets for discoloration, mold, or softening, and discontinue use if any changes are observed. Note: After opening, ensure the bottle is tightly closed after use and avoid storing or using in humid environments. If the sealed packaging is damaged and the medication has not been used for an extended period, it is advisable to discard it.

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