Automated moderation by the companies is to blame for failing to differentiate public health posts from those promoting drug use, according to pill-testing groups.
A number of organisations have reported the same issue of posts being taken down and their users being blocked or banned, with advocacy group the Australian Injecting and Illicit Drug Users League urging Australia's eSafety Commissioner to step in.
The landscape of drugs in Australia and globally has dramatically changed in recent decades, with a far higher proportion of novel and potentially dangerous substances on the market, Pill Testing Australia executive officer Steph Tzanetis said.
"The drug market is really different now compared to about 15 years ago, and it needs to be monitored," she told AAP.
In one instance, a warning about strong MDMA and nitazenes - a synthetically produced opioid more potent than fentanyl - was removed three days before a major summer festival and an appeal to have the post reinstated was rejected.
Other flagged posts by Meta include harm-reduction advice to prevent accidental overdoses, including warnings about "double-strength" MDMA, and recommendations to reduce dosage if testing isn't available.
"We make a point of complying with the guidelines of the social media platforms," Ms Tzanetis said.
"It does seem as though content is being removed because of the moderating systems that are used not being able to differentiate consistently whether something has a public health benefit."
Pill Testing Australia takes part with other groups, including CanTEST, and in a Commonwealth-funded drug early warning system.
As well as raising public awareness, the warning system is used by on-site medical teams, paramedics and emergency departments to help them provide potentially life-saving care.
"Put simply, Meta is silencing health workers who are simply trying to stop people from overdosing," Australian Injecting and Illicit Drug Users League chief executive John Gobeil said.
The organisation is urging eSafety Commissioner Julie Inman Grant to compel Meta and TikTok to restore content and users that have been removed on the basis of drug-related community standards violations.
It is also calling for the companies to establish clear pathways for public health organisations to have content reviewed by human moderators before automated removal.
"We know Meta will remedy this if regulators force them, but otherwise won't bother to teach its algorithm how harm reduction saves lives," Mr Gobeil said.
Surveys have shown the majority of Australians support pill testing. Government-sanctioned services are offered in Victoria, NSW and the ACT.
Pill testing was also taking place in Queensland until September, when the state government legislated to stop the practice.
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