Three US doctors have been charged over a scheme to make and sell a fake Botox drug which left four people paralysed.
Dr Livdahl says doctors were warned not to use his drug on patients
Dr Chad Livdahl and Dr Zarah Karim are accused of supplying a much stronger, black-market form of the approved Botox anti-wrinkle injection, at cheap rates.
Dr Bach McComb is charged with accidentally paralysing his girlfriend, himself and two others with the fake drug. He remains in hospital.
Mr Livdahl, who denies the charge, said his drug was marked for research.
Botox is a government-approved wrinkle treatment which works by using a weakened form of the botulism toxin temporarily to paralyse facial nerves that cause wrinkles.
Botox injections have leapt in popularity in recent years, with the British Association of Cosmetic Doctors recently saying the UK market was growing by 30% to 40% a year.
Dr Livdahl and Dr Karim, who run a firm based in Arizona, are accused of creating a black-market substitute for Botox using laboratory vials of the toxin intended for research purposes.
About 200 doctors across the US received vials of the substance from the pair, US lawyer Marcos Daniel Jimenez claimed.
Dr Livdahl, a microbiologist, said his product was labelled as being for research only and that doctors were warned not to use the substance on humans as a substitute for Botox.
An investigation was launched in November after Dr McComb allegedly injected himself, his girlfriend and two other people with the substance at a Miami clinic.
Dr McComb and a woman remain in hospital in New Jersey, prosecutors said.
A couple in their 50s from Palm Beach, Florida, who were injected by Dr McComb, were also hospitalised and are now recovering at a clinic, the AFP news agency said.
The doctors could face more than 20 years in prison and heavy fines if convicted on charges of conspiracy, fraud and misbranding a drug.