Some executions in the U.S. have been put on hold because of a shortage of one of the drugs used in lethal injections from coast to coast.

Several of the 35 states that rely on lethal injection are either scrambling to find sodium thiopental — an anesthetic that renders the condemned inmate unconscious — or considering using another drug. But both routes are strewn with legal or ethical roadblocks.

The shortage delayed an Oklahoma execution last month and led Kentucky's governor to postpone the signing of death warrants for two inmates. Arizona is trying to get its hands on the drug in time for its next execution, in late October. California said the shortage will force it to stop executions on Friday, three hours after an inmate is scheduled to die, when its stock expires.

The sole U.S. manufacturer, Hospira Inc. of Lake Forest, Ill., has blamed the shortage on unspecified problems with its raw-material suppliers and said new batches of sodium thiopental will not be available until January at the earliest.

Nine states have a total of 17 executions scheduled between now and the end of January, including Missouri, Ohio, Oklahoma, Tennessee and Texas.

"We are working to get it back onto the market for our customers as soon as possible," Hospira spokesman Dan Rosenberg said.

But at least one death penalty expert was skeptical of Hospira's explanation, noting that the company has made it clear it objects to using its drugs for executions. Hospira also makes the two other chemicals used in lethal injections.

Sodium thiopental is a barbiturate, used primarily to anesthetize surgical patients and induce medical comas. It is also used to help terminally ill people commit suicide and sometimes to euthanize animals.

Thirty-three of the states that have lethal injection employ the three-drug combination that was created in the 1970s: First, sodium thiopental is given by syringe to put the inmate to sleep. Then two other drugs are administered: pancuronium bromide, which paralyzes muscles, and potassium chloride, which stops the heart.

Ohio and Washington state use just one drug to carry out executions: a single, extra-large dose of sodium thiopental.

Hospira has blamed the shortage on "raw-material supplier issues" since last spring, first promising availability in July, then October, then early 2011. The company has refused to elaborate on the problem. But according to a letter obtained by The Associated Press from the Kentucky governor's office, Hospira told state officials that it lost its sole supplier of the drug's active ingredient and was trying to find a new one.

As for the possibility of obtaining the drug elsewhere, the Food and Drug Administration said there are no FDA-approved manufacturers of sodium thiopental overseas.

Switching to another anesthetic would be difficult for some states. Some, like California, Missouri and Kentucky, adopted their execution procedures after lengthy court proceedings, and changing drugs could take time and invite lawsuits.

Obtaining sodium thiopental from hospitals does not appear to be an option, either. Sodium thiopental has been largely supplanted by other anesthetics in the U.S., and hospitals do not stock much of it.

Also, drug purchasing and use rules — and ethical guidelines that bar the medical profession from getting involved in executions — could prevent hospitals from supplying prisons with the drug, according to industry experts.

"Many of these cases, the victims have waited for 20 years, some of them longer than that. If we're out of that drug, we need to have an alternative," said Tennessee state Sen. Jim Tracy. Tennessee said it has enough of the drug for a November execution and expects to be able to carry out another in December.

Last spring, Hospira, a publicly traded company, sent a letter to all states outlining its discomfort with the use of its drugs for executions, as it has done periodically.

"Hospira provides these products because they improve or save lives and markets them solely for use as indicated on the product labeling," Kees Groenhout, clinical research and development vice president, said in a March 31 letter to Ohio, obtained by the AP. "As such, we do not support the use of any of our products in capital punishment procedures."

Jonathan Groner, an Ohio State University surgeon and death penalty opponent who researches the issue, speculated the real reason for the unavailability of sodium thiopental is that its medical uses "have shrunk to the point that the company doesn't want to make a drug that has no use but to kill people."

However, Rosenberg, the company spokesman, said the shortage has nothing to do with that.

Last month, an Oklahoma judge delayed the execution of Jeffrey Matthews when the state tried to switch anesthetics after running out of its regular supply in August. Matthews was convicted of killing his 77-year-old great-uncle during a 1994 robbery. Oklahoma finally found enough sodium thiopental from another state, but the court-ordered delay continues.

A few weeks ago, Kentucky's governor held off signing death warrants — which set execution dates and allow executions to proceed — for two inmates because the state is almost out of sodium thiopental. The state's lone dose hits its expiration date Oct. 1.

Kentucky officials said they have contacted other states unsuccessfully in a search for sodium thiopental and have gotten calls from states looking for the drug.

Kent Cattani, Arizona's top death penalty prosecutor, said Wednesday that the state doesn't have the drug and he is not optimistic it can be obtained in time for the Oct. 26 execution of Jeffrey Landrigan, who was sentenced to death for stabbing and strangling a man in 1989. But later, an Arizona Corrections Department spokesman said the agency has placed orders for sodium thiopental and expects to have it by next week.

Georgia pressed ahead with an execution Monday night, putting Brandon Joseph Rhode to death for the 1998 killings of Steven Moss, 37, his 11-year-old son Bryan and 15-year-old daughter Kristin during a burglary. Georgia's Corrections Department said it has an "appropriate supply" of sodium thiopental. The California attorney general's office had said it only has enough of the drug for Thursday's scheduled execution of Albert Brown, who was condemned to die in 1982 for the rape and murder of a 15-year-old girl, though a federal appeals court ordered a trial judge late Monday to reconsider his ruling that paved the way for the execution.

Virginia apparently had enough of the drug Thursday to execute Teresa Lewis, the first woman put to death in the U.S. since 2005. But officials suggested the state could have a problem after that, though Virginia has no executions scheduled.

"We are in the same position as every other state regarding this matter," said Larry Traylor, Virginia prisons spokesman. He would not be more specific.

Missouri has enough for an October execution, but its supply expires in January.

Ohio, which spends about $350 for the drug for each execution, ran out of the amount state procedures call for just three days before a May 13 execution. The state obtained enough in time but won't say where.

Prisons officials in Texas, the nation's busiest death penalty state, refused to discuss how much sodium thiopental they have on hand, saying the information could inflame protesters outside the death house, and "people could get seriously hurt or killed."