Because of the numerous health benefits it has been linked with, aspirin is often hailed as the "wonder drug."
Earlier this month, it was announced that researchers from the UK would be embarking on the biggest clinical trial of aspirin to date - the Add-Aspirin phase 3 trial - investigating whether the drug is effective for preventing cancer recurrence through a study of around 11,000 people.
The announcement has caused much excitement in the medical world, with many health experts claiming the trial could be "game-changing" if the drug is found effective, offering a non-expensive strategy to improve survival for cancer patients.
Cancer is just one in a long line of illnesses that aspirin may combat. But in the midst of potential health benefits comes a number of risks, a fact some health professionals believe is often overlooked.
"Because it's been around a long time people think 'it must be safe and it can't do me any harm,'" Prof. Peter Weissberg, medical director of the British Heart Foundation in the UK, told The Independent. "They are taking it 'just in case,' but it's much more dangerous than some other drugs which people get concerned about, like statins."
In this Spotlight, we take a closer look at the potential health benefits of aspirin, as well as the risks associated with the drug.
Aspirin: one of the most commonly used drugs worldwide
Aspirin is a drug that was developed by German research chemist Felix Hoffman, of pharmaceutical company Bayer, in 1897.
Hoffman created aspirin by developing a process to synthesize acetylsalicylic acid (ASA) - a synthetic derivative of a compound called salicin, which is found naturally in plants such as the willow tree.
Early clinical trials of aspirin found it was an effective treatment for pain, fever and inflammation. It is believed the drug produces these effects by inhibiting the production of pain-producing chemicals called prostaglandins. As such, aspirin is commonly used to help ease headache, muscle pain, toothaches and common colds, as well as swelling in arthritis.
More recently, however, researchers have discovered aspirin may also be an effective blood thinner, preventing the formation of blood clots in the arteries by blocking the production of a prostaglandin called thromboxane, which plays a key role in blood clotting.
The possible risks of aspirin use
However, as with any drug, there is a risk for side effects with regular aspirin use.
One of the most severe side effects of regular aspirin use is gastrointestinal bleeding, which can raise the risk of developing a stomach ulcer. If one already has a stomach ulcer, taking aspirin could cause further bleeding and be potentially life-threatening.
Aspirin may also interact with other drugs and increase risk of internal bleeding, particularly drugs with anti-clotting properties, such as warfarin, apixaban and dabigatran. Taking aspirin with some dietary supplements, such as evening primrose oil and fish oil, may also raise internal bleeding risk.
Studies have associated aspirin use with increased risk of age-related macular degeneration.
Some individuals are allergic to aspirin, with people who have asthma most at risk. An allergic reaction to the drug may cause swelling of the lips, mouth or throat, breathing problems and a skin rash.
Other side effects of aspirin include headache, nausea and vomiting, tinnitus and bruising.
Some studies have linked aspirin use with increased risk for other health conditions. In 2013, for example, a study published in JAMA Internal Medicine suggested long-term use of the drug may increase the risk of age-related macular degeneration - the primary cause of blindness among older adults.
Previous research has also linked aspirin use to greater risk for Reye's syndrome - a rare disorder characterized by swelling in the brain and liver, most common among children and teenagers.
Despite these potential risks, however, aspirin has become one of the most widely used over-the-counter drugs around the globe; more than 100 million standard aspirin tablets are produced every year.
But people are not just using the drug to relieve the odd headache or cold. It seems aspirin is growing in popularity as more people are taking the drug regularly with the aim of preventing numerous health conditions for which studies have suggested it is effective against.
Aspirin and heart health
As mentioned previously, one of the many benefits of aspirin is believed to be its ability to prevent the formation of blood clots.
Last year, Medical News Today reported on a study by researchers from Australia that found individuals with venous thromboembolism (VTE) - a condition comprised of deep vein thrombosis (blood clots in the legs) and pulmonary embolism (in which a blood clot breaks off and travels to the lungs) - saw a 42% reduction in blood clot recurrence with a 100-mg dose of aspirin daily.
This and numerous other studies hailing the anticoagulant properties of aspirin have led to recommendations that people at high risk for heart attack or stroke may benefit from daily aspirin therapy.
The American Heart Association (AHA), for example, recommend daily low-dose aspirin - under the instruction of a health care provider - for heart attack survivors and others at high risk of heart attack.
And last month, MNT reported on new guidelines issued by the US Preventive Services Task Force (USPSTF) that recommend daily low-dose aspirin for heart attack and stroke prevention for individuals aged 50-59 who are at high risk for cardiovascular disease.
The debate over whether aspirin should be administered to prevent first heart attack or stroke, however, continues. Last year, the US Food and Drug Administration (FDA) concluded that, while daily aspirin use can help prevent heart attack and stroke in high-risk individuals, there is insufficient evidence to suggest it is beneficial for primary prevention.
But despite the FDA's conclusion, a study reported by MNT earlier this year revealed that 1 in 10 patients in the US are inappropriately receiving daily low-dose aspirin to prevent a first heart attack or stroke.
First study author Dr. Ravi S. Hira, of the Baylor College of Medicine in Houston, TX, said the findings are a concern because the risks of daily aspirin use may outweigh the benefits for healthy individuals.
"Major coronary events are reduced 18% by aspirin, but at the cost of an increase of 54% of major extracranial bleeding," he explained. "Each two major coronary events have shown to be prevented by prophylactic aspirin at the cost of one major extracranial bleed. Yet, primary prevention with aspirin is widely applied."
What is more, some studies have associated regular aspirin use with increased risk of hemorrhagic stroke - a type of stroke caused by a blood leakage in the brain.
On the next page, we look at some of the other risks and benefits of aspirin use.