Amitriptyline 25C rule that everyone using it for pain or migraine must follow

As temperatures are set to rise again there is a rule that anyone who uses the commonly prescribed medication needs to be aware of

14:42, 19 Jun 2026 Updated 14:43, 19 Jun 2026

Millions of people use amitriptyline in the UK for health issues ranging from pain relief through to depression . When the medication was first licensed in the 1960s is was used as an antidepressant however today it is more likely to be prescribed to treat nerve pain and prevent migraine .

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Figures show more than 15 million items of the drug were dispensed in the UK in 2022-23 with higher doses for those using it for depression than those taking it as pain relief. There is strict guidance around taking the medication, including taking it at night, as it can make people feel tired. Also, while people can drink alcohol while using it, they should stop drinking if it makes them feel sleepy.

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Amitriptyline users must also be aware of some symptoms to look out for of side effects of the medication These include:

Constipation

Feeling dizzy

Dry mouth

Feeling sleepy or tired

Difficulty peeing

Headache

However there is another rule people need to be aware of as temperatures rise over the summer. This weekend, parts of the country are forecast to reach 32C.

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The UKHSA has issued an amber heat health alert for the East of England, South East, South West and London until 8pm on Tuesday June 23 while a yellow heat alert is in place for the West Midlands and East Midlands over the same period.

According to the amitriptyline patient leaflet, high temperatures can affect the medication. It advises: "Store below 25C in a dry place , protected from light."

The Medicines and Healthcare products Regulatory Agency previously issued a warning about medicines in a heatwave - including amitriptyline. It warned: "Most medicines need to be stored at temperatures below 25°C. But cars, trains and buses can heat up quickly during the summer, and rooms with direct sunlight can get much hotter than you’d think. Even bags and pockets can get warm enough to cause problems, especially if you’re out all day or at a festival, sports event, or the beach.

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"Heat can break down the active ingredients in medicines, meaning they might not work when you need them. That includes tablets, inhalers, hormone patches, insulin, and EpiPens. Some packaging will give clear storage instructions, but not all medicines come with a visible warning."

It added: "If your medicine has changed colour, developed an unusual smell, changed texture, or looks different in any way, this could signal heat damage. Ask your pharmacist for advice.

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"If you’re at home, check the patient information leaflet for storage instructions and keep medicines in the coolest part of the house, away from direct sunlight. If you’re travelling, avoid leaving them in parked vehicles or warm bags. A cool bag can help if you’re going to be out all day.

"Heat damage can also affect how much medicine your body absorbs, potentially making your usual dose too strong or too weak. If you notice any changes in how you feel or how well your medicines seem to be working during hot weather , speak to your pharmacist or doctor."