A nurse who stole drugs while working at a hospital in Leeds has been jailed for three years.
A jury at Leeds Crown Court heard how Emma Webster took painkillers from the city's General Infirmary between August 2001 and June 2002.
The mother-of-three, of Warley View, Bramley, was found guilty of theft, falsifying records and forgery.
During the trial it emerged Webster, 33, had been caught stealing drugs before while working in Bradford.
The court heard one ward at Leeds General Infirmary had used one ampoule of pethidine in a year, but when agency nurse Webster arrived, it used 56 in the first month she was there.
She injected patients with sterile water, which she had substituted for the painkiller, the jury heard.
Leeds Teaching Hospitals NHS Trust assured patients that recruitment procedures had been changed after it emerged Webster had been caught stealing drugs while working at Bradford Royal Infirmary.
A spokesman said: "When the offences came to light, we carried out a thorough board-level investigation to identify any weaknesses in our systems and processes.
"As a result, our relationship with nursing agencies has been overhauled.
"A specific policy has been introduced to ensure that temporary staff cannot find themselves in charge of a ward area, and this has been supplemented by some of the strictest medicine control policies anywhere in the country.
"We are confident that we have learnt the lessons highlighted by this case and that measures are now in place to prevent a repeat."