Medsafe has labelled ibuprofen as a "safety concern" after research discovered a possible link to infertility in men.

However, the New Zealand Self Medication Industry [NZSMI] says the research used a small number of participants taking a "higher than normal" amount of the drug.

In a world first, a group of European researchers carried out a study on 31 healthy young men.

Fourteen took three ibuprofen a day for six weeks, while the other 17 took placebo tablets.

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The results, published in the Proceedings of the National Academy of Sciences showed those exposed to ibuprofen experienced "compensated hypogonadism," a condition prevalent among elderly men and associated with reproductive and physical disorders.

The study was sparked due to concern raised over declining reproductive health in men and increasing evidence "from recent years" showing exposure to analgesics could "generate negative endocrine and reproductive effects during fetal life".

Researchers said ibuprofen was "especially interesting" because of its increasing use in the general population and in particular by elite athletes.

Chris James, general manager of Medsafe said it had identified the study represented a safety concern.

"Despite this study, there have been no complaints recorded by the Centre for Adverse Reactions Monitoring.

"As with all safety concerns, we will review all the available information and consider the strength of the evidence before deciding if we need to take further action."

As with all medicines, it continued to monitor the safety of ibuprofen.

Scott Milne, executive director of the New Zealand Self Medication Industry [NZSMI] appreciated the research but said it needed to be kept in context.

"It also has to be evaluated alongside other research and in this case the sample space is very small, the dosages used are higher and longer than normal over-the-counter recommendations."

NZSMI represents companies involved in the manufacture and distribution of non-prescription consumer healthcare products in New Zealand.

The study involved men taking the drug three times a day for six weeks.

The average prescription was for between five and 10 days, he said. However, there were people who used the drug for those lengths but they were closely monitored by a medical professional.

"They would be under the supervision of their GP or the very least their pharmacist who would say, 'hey Bob, this has been going on a while, should we be doing something else?'."

There had been "tens of thousands" into ibuprofen use but this was the first he was aware of it linking to fertility issues.

"We're not certainly dismissing it and i would imagine it could spark further in-depth study which again is valid."

Dr John Peek, general manager at Fertility Associates, said the study couldn't state how ibuprofen might affect fertility - but raised questions.

"This type of drug effect on the testes of adult men is usually reversible once the drug is removed, although it can take some months for the effects to wear off. This study can't tell us how ibuprofen might affect fertility – but it raises questions."

While the study didn't see an effect on blood levels of male or female sex hormones, there was an increase in the level of the hormone [LH] which drives sex hormone production by the pituitary gland.

"The main finding came from taking pieces of testis tissue and exposing these to ibuprofen in a laboratory dish – ibuprofen reduced the amount of various hormones being made in the testis tissue."

However, more dangerously, exposure to various drugs and substances, including non-steroidal anti-inflammatory drugs, as the testes and ovaries develop could have an effect on the foetus.

"Exposure at this time is probably irreversible, and could affect fertility lifelong. There is evidence that ibuprofen could reduce the number of eggs that develop in the female foetus."