As temperatures in parts of Australia exceed 40°C during a record-breaking heatwave, medical experts warn that common medications can significantly impair the body's ability to handle extreme heat.
How Medications Affect Heat Tolerance
According to medical experts and the Pharmacy Guild of Australia, certain prescription and over-the-counter medications can impair the body's ability to regulate temperature. These effects occur through several mechanisms:
- Altered sweating patterns: Some medications reduce the body's ability to sweat, which is responsible for approximately 90% of heat loss.
- Increased dehydration risk: Certain drugs cause fluid loss, increasing vulnerability to heat stress, heat exhaustion, and heat stroke.
- Reduced blood flow regulation: Some medications interfere with the body's ability to redirect blood flow toward the skin for cooling.
"Individuals should continue taking prescribed medications while implementing extra precautions in hot conditions."
— Professor Trent Twomey, National President, Pharmacy Guild of Australia
Specific Medication Categories Affected
Reports identify the following medication types as potentially affecting heat response:
- Mental health medications: Some antidepressants and ADHD medicines may reduce heat tolerance and slow the body's cooling process.
- Cardiovascular medications: Diuretics and beta-blockers can impair cooling mechanisms or increase dehydration risk.
- Other medications: Drugs for allergies (antihistamines), constipation, acne, migraines, and some non-prescription painkillers may affect sun sensitivity or heat regulation.
Medical sources note that heart and diabetes medications can lead to acute kidney injury if an individual becomes dehydrated while continuing their dosage.
Vulnerable Populations
Older adults face increased risks due to age-related physiological changes:
- Reduced sweating ability: Individuals over 75 years old often experience diminished sweating capacity.
- Cardiovascular strain: The heart works harder to redirect blood to the skin for cooling while meeting oxygen demands of other organs.
- Existing health conditions: Heart, lung, and kidney diseases, as well as diabetes, can be exacerbated by heat.
- Social factors: Living alone, reduced mobility, cognitive conditions, and potential reluctance to use air conditioning due to energy costs are noted as additional risk factors.
Proper Medication Storage
The Pharmacy Guild and medical sources advise that medication storage is critical during high temperatures:
- Most tablets require storage below 30°C (some below 25°C) in cool, dry places away from direct sunlight.
- Certain medications, including insulin, weight-loss injections, and liquid antibiotics, require refrigeration.
- Storing medication in vehicles is discouraged due to temperature fluctuations.
- Medication that may have degraded due to improper storage should be replaced at a local pharmacy.
Recognizing Heat-Related Illnesses
Multiple sources outline a progression of heat-related conditions:
Heat Stress:
- Symptoms include tiredness, dizziness, weakness, muscle cramps, irritability, and general discomfort.
- In older adults, signs may include unusual tiredness, lethargy, loss of balance, confusion, or changes in urine frequency and color.
Heat Exhaustion:
- Symptoms include core body temperatures up to 38°C, reduced sweating, nausea, vomiting, headaches, and fainting.
Heat Stroke (Medical Emergency):
- Core body temperatures can reach 40.5°C or higher.
- Symptoms include confusion, reduced alertness, hot and dry skin (indicating failure of heat regulation), and loss of consciousness.
- Immediate medical attention is required.
Environmental and Physiological Factors
Reports note that risk is not solely dependent on air temperature:
- Humidity: High humidity reduces sweat evaporation, hindering the body's primary cooling mechanism.
- Sun exposure: Ambient temperatures recorded in the shade can be up to 15°C lower than temperatures in direct sunlight.
- Wind: Wind can aid or hinder cooling depending on conditions.
- Clothing: Certain clothing types can impede sweat evaporation.
"Extreme heat causes the heart to work harder to maintain blood pressure, increasing heart attack risk for those with underlying conditions."
— Professor Ollie Jay, University of Sydney's heat and health research centre
Dr. Arnagretta Hunter, a cardiologist at the Australian National University, noted that warm evening temperatures reducing overnight cooling can increase hospital admissions for cardiac and kidney problems.
Safety Recommendations
Multiple sources provide the following guidance:
- Stay hydrated: Consume adequate fluids.
- Seek cool environments: Use air conditioning or visit public spaces such as shopping centers or libraries.
- Efficient cooling: Setting air conditioners to 26–27°C with a pedestal fan can reduce electricity consumption.
- Direct cooling: Immersing hands and forearms in cool tap water for ten minutes every half hour can lower body temperature.
- Fans: Wetting skin or clothing combined with a fan can enhance cooling. However, sources note that fan effectiveness may decrease for older adults between 33–37°C, and above 37°C, fans might increase body temperature if sweating is insufficient.
- Sun protection: Increased sun protection is recommended for those taking medications that heighten sunlight sensitivity.
Community and Emergency Response
Check on older family members and neighbors during heatwaves. If individuals exhibit symptoms of heat stroke—such as slurred speech, confusion, fainting, or hot, dry skin—emergency services should be contacted immediately.
Individuals taking regular medication are advised to consult a general practitioner or pharmacist regarding potential heat-related risks and necessary precautions. Free Home Medicines Reviews are available through GPs.
Historical Context
Reports indicate that prolonged exposure to temperatures around 49°C or higher is considered unsafe. In some regions, temperatures exceeding 50°C have contributed to hundreds of deaths. The heatwave preceding Australia's Black Saturday bushfires in 2009, which killed 173 people, was estimated to have caused an additional 374 excess deaths.