According to US media reports, Pike's lawyers stated that two syringes of "pentobarbital" were administered to their client for the execution of her death sentence at the Riverbend Maximum Security Institution in Nashville, the state capital.
However, the lawyers stated that despite this, their client did not completely lose consciousness and her heart continued to beat.
Journalists observing the execution reported that the procedure took longer than usual, that Pike showed signs of life such as breathing and snoring despite the injections, and that the curtain showing the execution chamber was closed several times.
Pike was later transferred to a healthcare facility outside the prison.
Tennessee Governor Bill Lee ordered an investigation into the incident, and executions planned for the rest of the year in the state were also halted during the investigation period.
Pike was sentenced to death in 1995 for killing her classmate Colleen Slemmer when she was 18.
