A former Melbourne construction worker has been cleared of charges that he allegedly attempted to import fentanyl, cocaine and peptides into Australia.

All charges against Bernard McDowell were withdrawn during a brief hearing at the Melbourne Magistrates' Court on Friday.

The 33-year-old, who is also a triathlon competitor, had lost his job after it was alleged that he attempted to import a marketable quantity of fentanyl through Melbourne Airport on February 15 this year.

McDowell had been accused of moving the deadly synthetic opioid onto Australian shores after an interception by federal authorities.

He had also been charged with attempting to import a marketable quantity of cocaine via the airport on the same date.

McDowell, who lists his employment as a project manager within the construction and design industry, faced further accusations that he attempted to import Body Protection Compound 157 (BPC-157).

BPC-157 is an experimental synthetic peptide that is unapproved for human use and banned by anti-doping agencies.

The AFP charged McDowell shortly after the alleged drugs were seized.

But all charges were dropped, the Daily Mail understands, after testing on the peptides and fentanyl returned negative results.

Meanwhile, only a minuscule amount of cocaine was allegedly discovered. 

During the previous hearing, the Magistrates' Court had ordered testing on the alleged substances to be fast-tracked so that McDowell's matter could progress.

McDowell has competed in various triathlon events around the country and is well known in athletic circles.

News of his arrest came as a shock to those in the construction and running communities.

Fentanyl, which is roughly 100 times more potent than morphine, is widely trafficked on US streets and has been cited in the decline of cities such as San Francisco, Philadelphia and Baltimore. It is now beginning to surface in Australian cities.

It can be deadly in pinprick sizes and is often cut into other drugs, including heroin, cocaine, crack and ketamine, to increase the potency of those substances.

Fentanyl is sometimes pressed to appear like other prescription medications including Xanax and Valium. Users often have no idea they have taken the dangerous opioid.

Cheap to manufacture, the dangers are amplified in illegally produced fentanyl.

By contrast, peptides like BPC-157 are taking social media by storm, touted as the newest health and wellness fix, promising everything from anti-ageing benefits to rapid weight loss.

The supposed benefits range from enhancing your tan to speeding up muscle recovery, but much of the hype is driven by bold claims that lack solid scientific backing.

However, medical professionals are worried because some peptides being sold online are unregulated and have only been tested on animals.

'Peptides are short chains of amino acids that produce some effect on the body,' Dr Kieran Dang, chief medical officer of men's health platform Mosh, previously told the Mail.

'Insulin is a natural peptide, and semaglutide (aka Ozempic/Wegovy) is a synthetic peptide that's been properly studied and approved. What's trending now are experimental peptide drugs that have not been approved for human use.'

Dr Dang says the health risks are significant, particularly when it comes to 'peptide stacking'.

'Peptide stacking is when people inject multiple peptides at the same time to try to speed up recovery, muscle gain or fat loss,' he says.