Four batches of life-saving anti-allergy EpiPens have been recalled because they may fail to activate or require increased force — with potentially deadly consequences.

Affected batches: Batch number Expiry 5FA665 April 2017 5FA6651 April 2017 5FA6652 April 2017 5FA6653 April 2017

About 80,000 EpiPen 300 microgram adrenaline injection auto-injectors, that may contain a defective part, have been distributed worldwide, Mylan-owned Alphapharm said in a statement posted online.

The adrenaline auto-injectors are used to counter severe allergic reactions such as to food, medications and insect stings and bites.

"The failure of the auto-injector to activate may result in patients not receiving the required dose of adrenaline, resulting in the worsening of symptoms of anaphylaxis or anaphylactic reactions, which could be life-threatening," the company said.

The Therapeutic Goods Administration (TGA) said there had been two confirmed reports of the auto-injectors failing to activate correctly.

"The proportion of these auto-injectors that have been used is not known," the TGA said in an online statement.

The TGA advised checking the batch number and expiry date on either the EpiPen's label or on the end of its carton.

It said affected products could be returned to pharmacies and replaced free of charge.

But it advised keeping affected auto-injectors until they are replaced, and using them if required, "being mindful that you may need to apply more force than normal to activate it".

Alphapharm said: "At this time, EpiPen Jr 150 microgram adrenaline injection syringe auto-injectors and all other batches of EpiPen 300 microgram adrenaline injection syringe auto-injectors are unaffected and are not subject to this recall."