A popular anxiety drug taken by nearly 2million Americans is being recalled nationwide over a ‘life-threatening’ packaging error.

Sixteen lots of clonazepam sold by Par Pharmaceutical were printed with the wrong dosage strength on their labels.

The recall, issued by the manufacturer Endo Inc., affects 0.125 milligrams (mg), 0.25mg, 1mg and 2mg orally disintegrating tablets.

The incorrect dosing strength is printed on the carton the drugs are sold in, with the correct dose printed on the blister strips and tablets inside. 

Endo has warned patients to stop taking the recalled products immediately, saying there was a ‘reasonable probability’ they could suffer ‘life-threatening respiratory depression,’ when breathing becomes dangerously slow.

Pennsylvania-based Endo has blamed an unnamed ‘third-party packager’ for the error, which could be deadly if people accidentally take the maximum dosage of clonazepam.

There have been no reports of serious adverse events as a result of the error, the company said.

The above image shows the packaging for the Clonazepam drugs that were recalled

Patients who have the drug are being urged to throw it away immediately and to contact their pharmacy for a replacement.

Those who have ingested the recalled pills should contact their doctor immediately.

A total of 16 lots of the medication have been recalled, with each package containing 60 tablets packed in 10 blister strips each containing six pills.

It is not clear how many packages were are in a single lot.

Patients are being urged to check their medication’s lot number, found printed on the blister strips, to find out whether their dose is recalled. 

A list of the lot numbers can be found here.

In its voluntary recall, also published by the FDA, the manufacturer said: ‘Children and adults who inadvertently consume a higher dose of Clonazepam could be at increased risk for the adverse events of significant sedation, confusion, dizziness, diminished reflexes, ataxia and hypotonia.’

The above shows the packaging for the Clonazepam drugs that were recalled. They had the brand name Par Pharmaceuticals

Ataxia is loss of muscle coordination, leading to clumsy movements, and hypotonia is decreased muscle resistance to movement, making them appear floppy.

The manufacturer added: ‘There is reasonable probability for significant, possibly life-threatening, respiratory distress.

‘[This is] especially for patients with concomitant pulmonary disease, patients who have prescribed dosing near maximal dosing and patients also taking other medications that could cause additional respiratory distress.’

Clonazepam is commonly prescribed to treat seizures, epilepsy and panic disorders, a type of anxiety.

It works by raising levels of gamma-aminobutyric acid (GABA) in the brain, which helps to calm the nerve system and cause muscles to relax.

There are more than 23million prescriptions of the medication written in the US every year.