Summer has finally come to San Diego. Although it’s arriving a little late this year, it’s making up for the tardiness with some uncomfortably hot temperatures. However, for the many people suffering from chronic health conditions or taking certain medications, the heat can be more than just uncomfortable. It can be dangerous or even deadly.
Excessive heat puts extra stress on the heart — it’s work to make sweat — and certain medicines can make things worse, said Dr. Nassir Azimi, an interventional cardiologist at Sharp Grossmont Hospital.
“Some drugs disrupt the way our bodies usually regulate temperature, reduce bodily fluids or slow the heart, all of which can make people less able to cope with heat,” he said.
People taking medicines for some mental illnesses, heart problems and high blood pressure are especially vulnerable. But even drugs that most of us consider benign, such as antihistamines and motion sickness patches, can make it harder to handle the heat, doctors say.
Some medications place you at a greater risk of heatstroke and other heat-related conditions because they affect your body’s ability to stay hydrated and respond to heat. People who take medications that narrow blood vessels (vasoconstrictors), regulate blood pressure by blocking adrenaline (beta blockers), rid the body of sodium and water (diuretics), or reduce psychiatric symptoms (antidepressants or antipsychotics) need to be very careful during hot weather.
Stimulants for attention-deficit/hyperactivity disorder (ADHD) and illegal stimulants such as amphetamines and cocaine also make you more vulnerable to heatstroke.
During hot weather, people with mental illnesses get in trouble, especially when they have multiple risk factors, said Dr. Kenneth Duckworth, a Boston psychiatrist who is the medical director of the National Alliance on Mental Illness. The heat can affect them more seriously because they may be on an antipsychotic drug that interferes with internal temperature regulation, plus a diuretic for high blood pressure. Because these patients tend to isolate themselves, no one knows when they’re feeling too paranoid to open a window and could be suffering from dehydration and heat illness.
Dehydration can cause dizziness, rapid heartbeat and breathing, nausea, vomiting, and in extreme cases, kidney damage and unconsciousness.
Dehydration also may produce dangerous ill-effects from medications we take.
“When we get dehydrated we lose fluid through the skin, but the kidneys naturally retain fluids. That means that medications that are normally cleared through the kidneys are held onto, making them overly effective,” Azimi said.
So, for example, a dehydrated diabetic could end up being hypoglycemic (low blood sugar) if his insulin becomes too concentrated as it’s retained in the kidneys.
In addition to people with chronic medical conditions or on various medications, the very young, the old and the obese have more difficulty coping with the heat.
The ability to tolerate extreme heat depends of the strength of the central nervous system. In very young children, the central nervous system is not fully developed and in adults over 65, the central nervous system begins to deteriorate, which makes the body less able to cope with changes in temperature. Both age groups usually have difficulty remaining hydrated, which also increases risk.
An overweight person’s layers of fat make it extra difficult for the body to dissipate heat. Fat is a natural insulator that traps core body heat. The body cools itself by circulating blood to dissipate heat through the skin. A heavy person’s heart must pump harder to circulate blood on a hot day. Add in diabetic dehydration and other conditions common in the obese, and it’s a recipe for trouble.
Some meds and heat don’t mix
The following are some of the medications that can make you more susceptible to heat illness and heatstroke. If you take any medicines, ask your medical practitioner about special precautions you should take during hot weather.
• ACE inhibitors: Used for the treatment of hypertension and congestive heart failure, these medications widen or dilate blood vessels to increase the amount of blood the heart pumps to help lower blood pressure. When it’s hot, a patient on ACE inhibitors is more likely to become dehydrated, and when combined with low blood pressure caused by the drugs, severe lightheadedness and dizziness can result.
• ADHD stimulants: Drugs such as Ritalin, Adderal or Dexedrine are used for attention deficit/hyperactivity disorder. The stimulants increase blood pressure and make patients more vulnerable to heat stroke.
• Anticholinergic drugs: Often prescribed for spastic bladder, these drugs can inhibit the body’s ability to sweat, which is how your body cools itself. That lack of sweat can cause you to overheat.
• Antihistamines (Benedryl, etc.): These over-the-counter drugs are used to relieve congestion or sinusitis. They can increase the risk of dehydration and speed up the heart rate, making it difficult for the body to cool down and more vulnerable to the heat illness.
• Beta blockers: When we’re exposed to heat in the environment, our heart rate naturally goes up as do our metabolic demands. However, for a hypertensive patient on beta blockers, the heart rate is slowed down, “not a natural response to compensate for dehydration,” Azimi said. “So, on beta blockers patients are much more affected by the heat and get very tired.”
• Caffeine and alcohol: Both are dehydrating, said Candis Morello, pharmacist at University of California San Diego and associate professor of clinical pharmacy.
“Caffeine and alcohol make you urinate more and pull out electrolytes, which can cause dehydration and lead to electrolyte imbalance,” she said.
• Diuretics: These drugs rid your body of sodium and water and are commonly prescribed for people with congestive heart failure. During hot weather, patients should ask their doctor if they should cut back on their diuretic so they don’t become too dehydrated and ill.
• Erectile dysfunction drugs: Can increase sensitivity to sun and heat.
• Flomax (tamsulosin): Used for prostate problems, the drug relaxes arteries and can lower blood pressure. The drug can make men susceptible to dizziness and fainting, especially when dehydrated.
• Lithium: People who take lithium for bipolar disorder need to be especially careful. Lithium is a salt that becomes more concentrated in the body as people sweat away fluids.
• Psychiatric drugs: Particularly older antipsychotics and antidepressants can interfere with the body’s temperature-regulation system. People on these drugs can often feel hotter when the air is hot and colder when it’s cold. This makes patients more vulnerable to heatstroke.
• Scopolamine: Used in a skin patch for motion sickness, the drug causes dry mouth and dehydration, which can be intensified with heat.
• Vasoconstrictor drugs: These medications are used for the treatment of low blood pressure and are also in some nasal decongestants. The drugs cause contraction of blood vessels, which raises blood pressure and can make it difficult to cool down and tolerate heat.