New British research shows that too much of a good medication can be a bad thing.

In the study, repeated doses of paracetamol, known as acetaminophen (brand name Tylenol) in the United States, raised the risk of gastrointestinal, cardiovascular and kidney complications among those over 65.

The findings, published recently in the journal Arthritis Care and Research, illustrate the dangers of older people taking too much of the painkiller for chronic, painful conditions such as osteoarthritis.

Acetaminophen is used to temporarily relieve mild to moderate pain and fever. It is commonly included as an ingredient in cold and flu medications and is also taken on its own. It works by blocking signals in the brain that let people know when they're in pain and by affecting the chemicals that regulate their body temperature.

Evidence also suggests the widely used painkiller inhibits the production of prostaglandins, which are made by the body to deal with illness and injury.

Weiya Zhang, from the NIHR Biomedical Research Centre in the School of Medicine at the University of Nottingham, led the study.

"Due to its perceived safety, paracetamol [acetaminophen] has long been recommended as the first-line drug treatment for osteoarthritis by many treatment guidelines, especially in older people who are at higher risk of drug-related complications," Zhang noted in a university news release.

In the study, researchers analyzed data on over 180,400 people aged 65 and over who had been prescribed acetaminophen repeatedly (more than twice within six months).

Their health was then compared to nearly 402,500 people of the same age who had never been prescribed the drug repeatedly.

The findings showed that prolonged acetaminophen use was associated with an increased risk of gastrointestinal bleeding (36%); peptic ulcers (20%); heart failure (9%); hypertension (7%); and chronic kidney disease (19%).

“Whilst further research is now needed to confirm our findings, given its minimal pain-relief effect, the use of paracetamol as a first-line painkiller for long-term conditions such as osteoarthritis in older people needs to be carefully considered,” Zhang said.