• Apparently it's too easy to overdose, and potentially die, from this popular rheumatoid arthritis drug. (Getty Images)Source: Getty Images
Apparently it's too easy to overdose, and potentially die, from this popular rheumatoid arthritis drug.
Shami Sivasubramanian

8 Jun 2016 - 9:23 AM  UPDATED 8 Jun 2016 - 10:52 AM

A common prescription anti-inflammatory used to treat rheumatoid arthritis, called methotrexate, has been linked to at least eight deaths and about 90 hospitalisations since the year 2000, a new study shows.

Published in the Medical Journal of Australia this week, the research claims these deaths are due to patients taking the incorrect dosage of the drug. 

But leading researcher on the project, Dr Rose Cairns of the New South Wales Poison Centre, says the fatal dosage error is so alarming because it's an easy one for patients to make.

"It's actually quite an easy mistake to make," Dr Cairns tell SBS. "You take methotrexate once a week, unlike most tablets which are usually taken daily. So it's easy to forget. But if it's taken for three consecutive days, it can cause immunosuppression [a drastically lowered white blood cell count] which can be fatal."

However, the dire consequences from mistakenly taking the drug three days in a row are not apparent immediately. According to Cairns, it may take weeks for some patients to show symptoms of a crippled immune system and die from a typically recoverable illness.

Dr Cairns believes it is necessary to flag the risks of methotrexate, especially given the spike in the NSW Poison Centre's hotline calls over the last few year regarding incorrect dosages.

"From 2005 to 2013, the number of calls about the drug remained pretty stable, about four to nine cases a year. But in 2014, that number shot up to 16. And last year, the number was still pretty high at 13," says Dr Cairns.

If it's so easy to take the wrong dosage of methotrexate, it is worth letting patients self-administer? Perhaps restricting the drug to hospitals where a certified nurse can give out carefully measured dosages to patients is a better option.

Dr Cairns says her team considered that option, but find it could be more effective if pharmaceutical companies and manufacturers tweaked their packaging, tablet design and labelling first.

"Methotrexate comes in a pack of several tablets. But we recommend a pack with just one month's worth of dosages - so four tablets. It's harder to take a tablet every day if you only see four tablets in your pack.

"We also recommend labelling changes. So something in bold that reads 'WARNING: DO NOT TAKE DAILY'. And maybe something about the weekly dosage, too.

"Also the tablet is round and yellow, which looks very similar to folic acid which many patients take alongside methotrexate. So we suggest formulating the drug into a distinctly coloured tablet," recommends Dr Cairns.

Of course, in spite of the frightening side-effects of incorrect dosages, Dr Cairns emphasises "the drug should be safe if taken as prescribed".

To contact your state's Poison Centre, call 13 11 26.