US inmate Christa Pike says she woke up 'confused and in pain' after failed execution

US death row inmate Christa Pike has released her first public statement since her botched execution in September.

"There hasn't been a moment since that night when I haven't been in pain," she said in a statement released by her legal team on social media on Friday.

"My body hurts. My arms hurt. My hands hurt. My throat hurts. I still struggle to speak. And the pain isn't just physical. There is pain in my mind and in my soul."

Pike, 50, was discharged from hospital at the end of last month after surviving two lethal injections of the drug pentobarbital, which left her in a critical condition.

She has since been sent back to the prison where she has spent the last 30 years for murdering Colleen Slemmer in 1995.

Pike is thought to be the only person to have survived an execution attempt by lethal injection.

Her lawyers previously said she had suffered from pneumonia following the attempted execution, had significant swelling on her arms and was also unable to swallow.

"I am recovering, and I know that I am getting stronger," she said in her statement on Friday. "But healing is not the same as being okay."

Pike was 18 when she and her then-boyfriend, Tadaryl Shipp, beat, tortured and killed 19-year-old Slemmer, whom they had met at a job training camp for low-income young people.

Shipp was spared the death penalty because he was not legally an adult when the crime was committed. He remains in prison.