Botox, the "lunchtime facelift" injection, Botox Cosmetic (Botulinum toxin Type A) and Myobloc (Botulinum toxin Type B) have been linked in some cases to adverse reactions, including respiratory failure and death, following treatment of a variety of conditions using a wide range of doses, said the US Food and Drug Administration (US FDA).

In an early communication based on the FDA's ongoing safety review, the agency said the reactions may be related to overdosing. There is no evidence that these reactions are related to any defect in the products.

The adverse effects were found in FDA-approved and nonapproved usages. The most severe adverse effects were found in children treated for spasticity in their limbs associated with cerebral palsy. Treatment of spasticity is not an FDA-approved use of botulism toxins in children or adults.

The adverse reactions appear to be related to the spread of the toxin to areas distant from the site of injection, and mimic symptoms of botulism, which may include difficulty swallowing, weakness and breathing problems.

The FDA is not advising health care professionals to discontinue prescribing these products, the federal agency said.

The agency is currently reviewing safety data from clinical studies submitted by the drugs' manufacturers, as well as post-marketing adverse event reports and medical literature.

The notification is in keeping with the FDA's commitment to inform the public about its ongoing safety reviews of drugs, the US drugs safety watchdog said.

Earlier, an American public interest watchdog Public Citizen claimed that the two drugs has been linked to 16 deaths and a further 87 people needed hospital treatment for symptoms including muscle weakening and having difficulty swallowing.

Botox's maker, Allergan, which expects global sales of £500 million said that the risks associated with the drug were already made clear and there are no safety issues raised that are not already addressed in the labelling of Botox.