Periods of intense heat force the body to activate mechanisms to maintain its body temperature between 36.5 °C and 37.5 °C. These mechanisms include the active dissipation of heat through sweating and the passive transfer of excess heat to the skin, facilitated by increased blood flow resulting from a faster heart rate and vasodilation.

Certain medications may interfere with one or more stages of these adaptive mechanisms.

Those mentioned here are taken from the list of medicationsthat may reduce the body’s ability to adapt to heat waves published by the French National Agency for Medicines and Health Products Safety and from the list published by Observatory of Medications, Medical Devices, and Therapeutic Innovations for the Nouvelle-Aquitaine, Guadeloupe, and French Guiana regions.

Here are the key points to watch for, presented in eight questions

1. Which patients require close monitoring?

This includes all vulnerable patients:

• Infants, young children, and older adults 
• Patients with chronic conditions, disabilities, or dependence on care 
• Patients with cognitive impairments 
• Patients experiencing social isolation 
• Social vulnerability: living conditions or work environments exposing them to extreme heat

2. What are the main drug classes that require particular vigilance?

The College of General Medicine provides the following list:

• Diuretics 
• Laxatives 
• Antihypertensives (Angiotensin-converting enzyme (ACE) inhibitors and sartans) 
• Psychotropic drugs, particularly neuroleptics 
• Anticholinergics 
• Certain antiepileptics (topiramate and zonisamide) 
• Certain antidiabetics (SGLT2 inhibitors (gliflozins), DPP-4 inhibitors (gliptins), and GLP-1 receptor agonists) 
• Nonsteroidal anti-inflammatory drugs (NSAIDs) and aspirin at anti-inflammatory doses (> 500 mg/d) 
• Insulin, glucose meters, and test strips

Care should also be taken with transdermal patches as their effectiveness may be altered by sweating or dilation of blood vessels in the skin.

It may be helpful to reassess treatments that could exacerbate the effects of heat or dehydration, though it is not always necessary to modify or temporarily discontinue them.

As a reminder, NSAIDs and acetaminophen should be avoided in heatstroke.

3. Which medications can worsen heat exhaustion and heatstroke?

Heat exhaustion and heatstroke are the two main risks associated with excessive ambient heat. They can be exacerbated by certain medications.

• Medications that cause dehydration: 
  • Diuretics 
  • Laxatives 
  • Certain oral antidiabetics (eg, gliflozins) 
  • Certain antiepileptics (eg, topiramate, zonisamide) 
  • Acetazolamide (used to treat glaucoma) 
• Medications that may impair kidney function: 
  • All NSAIDs, including coxibs and aspirin at doses > 500 mg/d 
  • Certain antihypertensives (sartans and ACE inhibitors) 
  • Certain antidiabetics (gliptins and GLP-1 agonists) 
  • Certain antivirals (indinavir) 
  • All medications known for their nephrotoxicity (certain antibiotics, such as aminoglycosides and sulfonamides; certain immunosuppressants, such as cyclosporine and tacrolimus; and certain iodinated contrast agents) 
• Medications whose elimination may be affected by dehydration: 
  • Lithium salts 
  • Antiarrhythmics and digoxin 
  • Certain antiepileptics 
  • Insulin (risk for increased absorption rate, leading to hypoglycemia) 
  • Certain oral antidiabetic drugs, such as SGLT2 inhibitors (gliflozins) 
  • Statins and fibrates 
• Medications that disrupt thermoregulation: 
  • Centrally: 
    • Certain neuroleptics 
    • Certain antidepressants 
    • Lithium salts 
    • Triptans 
    • Buspirone 
    • Certain opioids (tramadol, dextromethorphan, and oxycodone). 
  • Peripherally: 
    • Anticholinergics (by decreasing sweat production) 
    • Peripheral vasoconstrictors (by limiting the narrowing of blood vessels in the skin). For example, pseudoephedrine, neosynephrine (prescribed for the treatment of nasal congestion) 
    • Certain antihypertensives, such as beta-blockers, and diuretics may inhibit the increase in cardiac output

4. Which medications can increase sweating?

These are parasympathomimetic medications:

• Pilocarpine 
• Anticholinesterases (donepezil, galantamine, rivastigmine) 
• Cholinesterase inhibitors (neostigmine) 

5. Which medications can worsen heat-related effects?

• Medications that lower blood pressure: antihypertensives and antianginals 
• Medications that impair alertness: sleeping pills, anxiolytics, neuroleptics, and certain antidepressants

6. Which medications carry a risk for photosensitization?

Many medications can cause photosensitization. The following list is not exhaustive.

• Topical skin medications: 
  • Anti-inflammatory gels (ketoprofen gels and diclofenac gels) 
  • Acne treatments (adapalene, isotretinoin, benzoyl peroxide) 
  • Anti-allergy ointments 
  • Certain skin antiseptics (chlorhexidine)
• NSAIDs, particularly piroxicam, diclofenac and ketoprofen, ibuprofen, aspirin, sulfasalazine, and mesalazine
• Isotretinoin 
• Certain antibiotics: quinolones (particularly fluoroquinolones), tetracyclines (particularly doxycycline), sulfonamides, trimethoprim, and dapsone
• Antimalarials (hydroxychloroquine and quinine) 
• Statins, fibrates, certain diuretics (hydrochlorothiazide, indapamide, and triamterene) 
• In cardiology: 
  • Antiarrhythmics (amiodarone) 
  • Calcium channel blockers (diltiazem, amlodipine, nifedipine, and felodipine) 
  • ACE inhibitors (captopril, fosinopril, and quinapril) 
• Oral antidiabetics, particularly sulfonylureas 
• Proton pump inhibitors (omeprazole, esomeprazole, rabeprazole, pantoprazole, lansoprazole, etc) 
• Certain anticancer drugs, for example, dacarbazine, fluorouracil, and methotrexate
• In neurology and psychiatry:
  • Neuroleptics (chlorpromazine, promethazine, and phenothiazines) 
  • Benzodiazepines 
  • Carbamazepine and lamotrigine
  • Certain antidepressants: imipramine, clomipramine, fluvoxamine, paroxetine, fluoxetine, citalopram, and St John’s wort-based medications
• Verteporfin (indicated for macular degeneration) 

7. What are the warning signs for antihypertensive medications?

• Orthostatic hypotension, as measured by the patient at home (systolic blood pressure below 90 mm Hg), following suggestive symptoms (eg, dizziness when changing position)
• Rapid weight loss of 2 kg (about 4.4 Ib) in 1 day, indicating dehydration

The presence of only one of these signs does not necessarily require medical consultation. However, treatment should be paused until temperatures return to normal and then resumed without modification, preferably after consulting the prescribing physician.

8. Which medications or medical devices are heat-sensitive?

• Suppositories, vaginal suppositories, and creams. Any change in appearance should prompt consultation with a pharmacist.
• Blood glucose meters, test strips, an reagents. Store them away from sunlight, high temperatures, and significant fluctuations in temperature and humidity
• Medications whose package insert specifies a storage temperature:
  • Below 25 °C or 30 °C: Deviations from standard precautions are permissible if they are occasional and brief (a few hours), provided these medications are not exposed to direct sunlight or left in a place where the temperature is high
  • Below 25 °C or 30 °C: Brief, occasional deviations are acceptable, provided the medications are not exposed to direct sunlight or high temperatures

This story was translated from Univadis French, part of the Medscape Professional Network.