Americans are taking medicines designed for fish because they want to save money and avoid going to a doctor, researchers fear.
Pet antibiotics including penicillin are available online for as little as $8.99 (£6.84) for a bottle of 30 pills.
Scientists found reviews of the unregulated drugs on treating human infections are popular among sick people in the US. The study did not apply to the UK.
The ‘alarming’ findings have prompted experts to warn that using antibiotics for animals could cause side effects or be unsafe for people.
They are also unlikely to cure an infection, meaning the patient’s symptoms could get worse in the meantime and bugs could build up a resistance to drugs.
Using antibiotics without a doctor’s guidance is one of the key drivers of antibiotic resistance, a growing global threat which is making once basic infections increasingly difficult to treat.
Research by pharmacy experts in the US revealed people are buying antibiotics intended for fish (stock image) and taking them themselves as a cheaper and faster alternative to going to a doctor
The study was done by the American Society of Health-System Pharmacists (ASHP) but it couldn’t say how many people were buying and using the drugs.
By looking at online reviews – the website used was not named – it found reviews of fish antibiotics which mentioned human use were nine times more popular than those which didn’t, suggesting they are being used.
Fish antibiotics may pose a particular problem because they can be bought over the counter, while those intended for dogs or cats cannot.
Dr Brandon Bookstaver, one of the researchers from the University of South Carolina, said: ‘While human consumption of fish antibiotics is likely low, any consumption by humans of antibiotics intended for animals is alarming.
‘Self-medication and the availability of antibiotics without healthcare oversight might contribute to increasing antimicrobial resistance and delayed appropriate treatment.
‘We were particularly concerned that the high volume of positive feedback on the comments about human use might encourage others to attempt to use these drugs.’
Dr Bookstaver and his colleagues made their findings in a ‘comprehensive review of the online fish antibiotic market’.
They found drugs for fish were readily available online in the US and prices ranged from just $8.99 (£6.84) to $119.99 (£91.26).
And many were the same antibiotics which are prescribed to people – amoxicillin, penicillin, ciprofloxacin, cephalexin, metronidazole, and sulfamethoxazole-trimethoprim.
Doctors’ appointment fees and drug costs could mean getting the drugs through a doctor would cost significantly more – uninsured patients could have to fork out hundreds of dollars and even those with insurance would have to pay deductible fees in excess of the cheapest fish drugs.
The team actually bought some of the drugs and did lab tests which found they were identical to medicines intended for humans.
But they warned the risk was not worth it. Quality control is looser on animal products, they said, and there was no guarantee they contain what is listed on the label – the real contents could be dangerous.
The researchers found that in online reviews, those which mentioned human consumption outranked the number of ‘likes’ on the animal-only reviews’ by ratio of nine-to-one.
In one instance, a seller even responded to a question from a customer and said fish pills were suitable for human use.
‘What might seem like a less expensive, easier way to treat an assumed infection can ultimately have very serious negative consequences,’ said Dr Michael Ganio, director of pharmacy practice and quality at the ASHP.
‘Unlike antibiotics for humans or other animals, these medications are completely unregulated by the Food and Drug Administration.
‘Even if the pills look the same, it’s impossible to know that medications purchased in this manner contain what the label says and are safe for humans.
‘Antibiotics, like all medications, should be dispensed from a licensed pharmacy after a diagnosis and prescription from a medical professional.’
Exposing bacteria to antibiotics in a way that doesn’t kill them can essentially train them to build up a tolerance and be more resistant to treatments in the future.
Because of medicines being overused in people and farm animals, leaking into the water supply and not being taken properly, this is now a growing problem around the globe.
The World Health Organization lists antibiotic resistance as one of its 10 biggest threats to humanity and infections such as pneumonia, tuberculosis, gonorrhoea and septicaemia are already getting harder to treat because of it.
Dr Bookstaver and his colleagues presented their research at the ASHP’s 54th Midyear Clinical Meeting and Exhibition this week.