Temperatures in the UK are soaring today but people on some medications need to take extra care (Image: Getty Images)
A health alert has been issued for individuals taking particular medications, warning of potentially dangerous reactions amid soaring temperatures. A pharmacist has urged those on these drugs to exercise additional caution as the mercury is forecast to reach 35C today.
Britain faces further records tumbling today following the nation’s hottest May day ever recorded. The country also logged its provisional all-time hottest meteorological spring temperature when Kew Gardens in south-west London reached 34.8C.
The Met Office identified 12 locations where the record was surpassed on Monday – spanning from Suffolk to Berkshire to Warwickshire – while 97 of its monitoring stations hit or exceeded 30C. Before that day, the all-time May record stood at 32.8C achieved in 1922 and 1944.
The anticipated peak for vast areas of southern England and Wales on Tuesday is 35C – which may climb to 36C, senior Met Office meteorologist Becky Mitchell said. Those predictions cover the Midlands, the south-east and south-west England, East Anglia, and South Wales.
Thunderstorms could develop during the afternoon, which will influence how high temperatures climb. Dipa Kamdar, Senior Lecturer in Pharmacy Practice at Kingston University, wrote on The Conversation website that: “The body uses several mechanisms to regulate temperature: sweating, blood flow to the skin and fluid balance. But some commonly prescribed drugs interfere with these processes, making it harder to stay cool.” She reviewed a selection of medications commonly prescribed throughout the UK, highlighting the need for extra vigilance.
Ms Kamdar pinpointed two specific categories of antidepressants – selective serotonin reuptake inhibitors (SSRIs) and tricyclics (TCAs) – as potentially making summer conditions harder to tolerate. These might include sertraline, fluoxetine (Prozac), citalopram amongst SSRIs and for TCAs, amitriptyline, nortriptyline, and lofepramine.
She explained: “They could even cause heat intolerance due to how they affect the body’s ability to sweat.” These antidepressants are thought to function partially by influencing neurotransmitter concentrations in the brain, primarily serotonin and noradrenaline. This may lead to reduced perspiration in some patients, which during hot weather could hamper the body’s cooling mechanism.
TCAs also elevate noradrenaline concentrations, a neurotransmitter that activates sweat glands. This can boost perspiration. Indeed, both SSRIs and TCAs can heighten sweating amongst users. Evidence suggests up to 14% of antidepressant users encounter this side-effect.
SSRIs may additionally disrupt the hypothalamus, the brain area that regulates body temperature and instructs the sweat glands to begin producing perspiration. However, this signal may be impacted by the elevated serotonin concentrations. Ms Kamdar clarified: “Since sweating is a key cooling mechanism, any disruptions to this process can lead to heat-related illness. Excess sweating may also cause dehydration if fluids aren’t replaced.”
Ms Kamdar detailed: “Antipsychotics are used to treat psychosis, which can occur in schizophrenia and bipolar disorder. They do this by blocking the neurotransmitter dopamine – which in turn affects levels of the neurotransmitter serotonin. This can disrupt the hypothalamus’s ability to sense and respond to changes in body temperature.
“As a result, someone taking an antipsychotic might not feel overheated or thirsty when it’s warm outside. This can result in low blood pressure and diminished heart function.
“The body then attempts to compensate by constricting the blood vessels and retaining heat. This consequently reduces perspiration and makes it more challenging to cool down effectively.”
Beta-blockers diminish heart rate and reduce the force of cardiac contractions. However, Ms Kamdar observed that this can restrict blood flow to the skin, hampering the body’s ability to release heat during hot weather. She continued: “Diuretics are also commonly used in the treatment of high blood pressure or heart failure. But as these drugs increase urine output, this may lead to dehydration and electrolyte imbalances during hot weather.
“With less fluid available, the body may struggle to sweat properly. If you become severely dehydrated, you might actually stop feeling thirsty. Blood pressure can also drop, which may cause dizziness or fainting – especially when standing up.”
Blood pressure medications such as Ramipril and Losartan can also heighten the risk of dehydration, she noted. “These drugs block a system in the body that helps control blood pressure, fluid balance and thirst. This may reduce your natural urge to drink, increasing dehydration risk when it’s hot.”
Prescribed amphetamines for ADHD, for instance, interfere with several brain chemicals, including dopamine and noradrenaline. These effects can elevate body temperature, speed up metabolism, and disrupt the body’s sweating mechanism, making it increasingly difficult to cool down, particularly during physical exertion or in warm conditions.
This could potentially result in dehydration, overheating, or even heatstroke. Stimulants may also suppress feelings of fatigue, causing individuals to overexert themselves without recognising the danger.
Insulin Ms Kamdar explained: “Warm temperatures cause the body’s blood vessels to dilate (widen) to aid in cooling off. However, this process results in faster absorption of insulin into the bloodstream due to increased blood flow to the area where insulin is injected – causing blood sugar levels to drop more rapidly.
“This can result in hypoglycaemia (low blood glucose level), potentially causing symptoms such as dizziness, shaking, sweating, irritability, and even loss of consciousness or seizures.
“Heat can also degrade insulin, reducing its effectiveness and making it unsafe. This is why insulin should be stored in the fridge until use – especially in summer. Damaged insulin will change appearance – turning cloudy or changing colour.”
To avoid heatstroke, Ms Kamdar suggests several preventative measures for those on common prescription drugs:
- Always check labels for storage instructions. Avoid leaving medications in hot places, such as in cars or on windowsills.
- Insulin isn’t the only drug affected by heat – inhalers and EpiPens can also malfunction or become less effective.
- Stay hydrated when it’s hot – unless your doctor has advised otherwise. Dehydration can actually worsen the effects of many medicines.
- For example, anti-inflammatory painkillers (such as ibuprofen) are more likely to cause kidney problems and bipolar medicines (including lithium) can become toxic if you’re dehydrated.
- Avoid peak heat hours and stay in cool environments when possible. Watch for warning signs of heat-related illness – such as dizziness, confusion, nausea or excessive sweating.
- Don’t stop taking your prescriptions medication without medical advice. If it’s affecting your ability to cope with the heat, speak with your doctor or pharmacist.
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