By Claudia Lauer, Associated Press

LITTLE ROCK, Ark. (AP) — An execution drug obtained by the Arkansas prison system this month appears to have been made by a subsidiary of Pfizer, even though the pharmaceutical giant has said it doesn't want its drugs to be used in executions.

The sale of the vecuronium bromide by an unknown third party may show how difficult it could be for manufacturers to prevent such sales in states such as Arkansas that have execution secrecy laws.

The Associated Press on Monday obtained redacted photos of the vecuronium bromide label from the Arkansas Department of Correction. It matches labels submitted to the National Institutes of Health by Hospira, Inc., which Pfizer bought last year. The AP also obtained the purchase orders for the drug, but the name of the third party that sold the drug to the department was redacted, in compliance with the state's execution secrecy law.

Pfizer announced in May it had put in place sweeping controls to make sure its distributors would not sell its drugs for use in executions. In an email Monday, company spokeswoman Rachel Hooper reiterated that position.

"We have implemented a comprehensive strategy and enhanced restricted distribution protocols for a select group of products to help combat their unauthorized use for capital punishment. Pfizer is currently communicating with states to remind them of our policy," Hooper wrote. She didn't address whether the company was aware of the sale of its subsidiary's drug to the Arkansas Department of Correction.

Maya Foa, who tracks pharmaceutical companies for the London-based human rights advocacy group Reprieve, defended Pfizer and Hospira, saying no pharmaceutical company wants its drugs used in executions.

"It is possible that Arkansas Department of Correction was able to access a left-over supply of Hospira inventory that was sitting in old distribution channels. This is, of course, a finite supply. Pfizer's new distribution system is extremely robust, and the company is committed to preventing the misuse of its medicines in executions," Foa said by email.

Records obtained by the AP show the state agreed to pay $1,849.33 for 100 vials of vecuronium bromide on July 11 and $2,982 for a purity analysis of the drug. That's almost 10 times less than the $18,478 the state paid in June 2015 for fewer doses of the drug.

Solomon Graves, a Department of Correction spokesman, said he couldn't comment on the price difference. He confirmed by email that the new supply of vecuronium bromide was not bought at a pharmacy outside of the U.S. and was not made by or obtained from a compounding pharmacy.

Asked whether the department knew or cared that a drug manufacturer said it didn't want its products used in executions, Graves responded: "Under the law, we cannot identify the company that made or sold the drugs, and I will not engage in hypotheticals."

The department already had a little more than 15 doses of midazolam, which expire in April 2017, and 16 doses of potassium chloride, which expire in January 2017.

In September, the AP identified the likely makers of the drugs the state purchased last year by comparing redacted Department of Correction photos of their labels with labels archived at the NIH and U.S. Food and Drug Administration. It appeared that an India-based company, Sun Pharma, made the expired supply of vecuronium bromide. A subsidiary of the England-based company Hikma appeared to make the midazolam, and Hospira appeared to make the potassium chloride.

At the time, neither Hospira nor Sun Pharma would say whether they would try to recall the drugs. Both issued statements saying they opposed the use of their drugs in executions, and their internal policies and controls were put in place to prevent the use of the drugs in lethal injections.

Hikma in 2013 recalled different drugs that the Arkansas Department of Correction obtained from a third-party seller for executions. The company attempted to verify that its drugs had been obtained last year, but the department declined to answer the company's questions, citing the secrecy law.

Executions in Arkansas had been largely halted since 2005 because of legal challenges and trouble obtaining execution drugs. In a bid to resume executions, the Republican-led Legislature passed the execution secrecy law last year. It requires the state to keep the details about its execution drugs secret, including the names of the drugs' makers and sellers.

Nine inmates challenged the law, saying it could put them at risk of being subjected to unconstitutional cruel or unusual punishment and that it reneged on a previous agreement by the state to share information about the sources of the its execution drugs.

The state Supreme Court upheld the law in a split decision last month. The inmates indicated they planned to appeal to the U.S. Supreme Court. Eight of their execution dates had already been set, but their executions were on hold pending the outcome of that appeal.

To Learn More:

With Pfizer Ban, States Lose Last Source of Lethal Execution Drugs (by Andrew Welsh-Huggins, Associated Press)

States Scour the Globe for Scarce Lethal Drugs, but Some Still Find Ways to Execute its Death Row Inmates (by Noel Brinkerhoff, AllGov)

Most Death Penalty States Hide the Names of the Suppliers of Execution Drugs (by Noel Brinkerhoff, AllGov)

Georgia Uses Secrecy Law to Obtain Lethal Drug for Execution of Mentally Disabled Prisoner (by Danny Biederman and Noel Brinkerhoff)

4 States Pass Laws Hiding Names of Suppliers of Death Penalty Drugs (by Noel Brinkerhoff, AllGov)