Early symptoms include dry mouth, difficulty breathing or swallowing, slurred speech, drooping eyelids and muscle weakness. -- PHOTO: AP

Public Citizen on Thursday asked US authorities to require the strongest possible warning, highlighted in a 'black box', on Allergan's Botox and Solstice Neuroscience's Myobloc.

Botox is famous for smoothing facial wrinkles but also has approved medical uses such as treating cervical dystonia, or rigid neck muscles. Myobloc is cleared only for the neck condition.

Both injections are made with forms of the botulinum toxin, which blocks nerve impulses to muscles and makes them relax.

Public Citizen said it reviewed 180 reports submitted to the Food and Drug Administration by manufacturers involving patients injected with Botox or Myobloc. The reports detailed cases of muscle weakness, difficulty swallowing or aspiration pneumonia, a serious condition caused by breathing a foreign material into the lungs.

Reports to the FDA do not prove a product caused a particular problem, but the agency uses them to look for patterns of potential complications. Experts believe most problems are under-reported to the agency.

Allergan projected in November that worldwide sales for Botox would top US$1.1 billion (S$1.6 billion) in 2007.

Sixteen cases reported to the FDA were fatal, including four involving children under 18, Public Citizen said.

Eighty-seven patients were hospitalised.

Dr Sidney Wolfe, director of Public Citizen's Health Research Group, said such problems can occur if botulinum toxin spreads from the injection site to places such as the oesophagus, causing partial paralysis. Instructions for Botox and Myobloc mention the issue but it is easy to miss, he said.

Public Citizen asked the FDA to order a black-box warning to highlight the concern, plus a letter to doctors. The agency also should require a consumer-friendly guide explaining the risks that would be handed out by doctors when the drug is injected, the group said.

'These significantly improved warnings to doctors and patients would increase the likelihood of earlier medical intervention when symptoms of adverse reactions to botulinum toxin first appear, and could prevent more serious complications, including death,' Public Citizen said in a petition to the FDA.

Early symptoms include dry mouth, difficulty breathing or swallowing, slurred speech, drooping eyelids and muscle weakness.

The group said European regulators have warned physicians to watch for signs of botulinum toxin complications.

FDA spokesman Karen Riley said the agency would not comment while the Public Citizen petition was under review. -- REUTERS