Health officials have issued an alert over a surge in the use of bootlegged sedatives and anti-anxiety medications during lockdown that have been linked to a string of hospital admissions and deaths.

Public Health England (PHE) warned that illicit drugs sold as benzodiazepines could have potentially fatal consequences, particularly when taken in conjunction with alcohol and certain painkillers.

In the alert, which was put out on July 24, PHE said the drugs were being marketed as the anti-anxiety drugs diazepam and alprazolam, and the sedative temazepam.

PHE said there was evidence linked to toxicology results from recent hospital admissions and deaths, as well as from seized caches of the tablets, that the counterfeit drugs were causing harm.

It advised users to watch out for a tablet with “DAN 5620” on one side and “10” on the other, as well as one marked “T-20”, “TEM 20”, “Bensedin” and “MSJ”.

Most of the dangerous tablets, sometimes referred to as “street benzos”, are blue but may come in other colours, PHE said, and may stain people’s mouths.

Often they have been packaged in blister packs or proper pharmacy tubs to make them appear legitimate, and may claim to contain a certain dose of approved drugs, such as diazepam.

In reality, they may not contain any genuine medicines and will instead have high-potency illicit benzodiazepines, an equivalent compound or another non-medical substance, PHE said.

The strength of street benzos can vary widely, putting the user at risk of overdose as they have no reliable measure of their intake.

Benzodiazepines impact brain activity and slow the central nervous system, which affects breathing.

They are even more dangerous when used with other substances that have the same effect such as heroin and other opioids, and the epilepsy medication and painkiller gabapentinoids.

Drug research and drug policy charity Release said it is still unclear where these bootlegged benzodiazepines are coming from, but that many are being supplied to dealers via the dark web.

It found that users are still primarily relying on face-to-face transactions to obtain the drug.

Niamh Eastwood, Release’s executive director, said some of the surge in the use of street benzos during lockdown had been driven by people normally dependent on heroin.

She told the PA news agency people who may have relied on begging or petty crime such as shoplifting had seen their income disappear overnight.

“One of the drivers of the increase, in the early part of lockdown was that heroin users lost income and couldn’t buy it so shifted to benzos which are significantly cheaper,” she said.

She said the bust of the “EncroChat” crime network by the National Crime Agency last month which saw over 700 arrests had also significantly disrupted the heroin market, causing many to switch to benzos.

Harry Shapiro, director of charity DrugWise, said the distribution of the drugs in industry-standard packaging allowed some dealers to convince buyers they were genuine medicines that had found their way onto the black market.

“If you make something look legitimate people then either believe that it is or con themselves into believing that it is until they find out otherwise,” he said.

PHE warned the drugs also impact mental health and can increase suicidal thoughts, particularly in young adults and people with alcohol or opioid addiction.

In April, the body advising the Government on drug use, called for three new synthetic benzodiazepines – flualprazolam, flunitrazolam and norfludiazepam – to be banned.

The Advisory Council on the Misuse of Drugs found these so-called “legal highs” had been linked to 12 deaths in the UK as of March 2020.