ST. LOUIS – A federal judge on Monday halted executions in Missouri until the state makes sweeping changes to ensure that inmates do not suffer excruciating pain when they are put to death.

U.S. District Judge Fernando Gaitan Jr. cited “numerous problems” with the state’s lethal injections, including a lack of a written protocol setting drug levels and a dyslexic doctor who is in charge of mixing the three drugs used.

Judge Gaitan said the state’s practices subject condemned inmates to an unnecessary risk of unconstitutional pain and suffering. Ruling in the case of condemned inmate Michael Taylor, he gave the Department of Corrections until July 15 to come up with a new protocol, and said no executions can occur until he approves it.

Judge Gaitan’s ruling is not binding anywhere but in Missouri, but the U.S. Supreme Court ruled this month that condemned inmates can make special federal court claims that the chemicals used in executions are too painful.

The Missouri corrections director, Larry Crawford, said in a hearing before Judge Gaitan two weeks ago that he would clarify the execution protocol. He testified after learning that the surgeon who is the sole person in charge of mixing the drugs had prepared a lower-than-expected dose of anesthesia for the last several inmates who were put to death.

The surgeon testified he had been administering 2.5 grams of thiopental, which is supposed to render the inmate unconscious and is the first of the three drugs Missouri uses in executions. Judge Gaitan ordered the state to use at least double that amount.

Judge Gaitan, who sits on the federal bench in Kansas City, also said he was concerned about the dyslexia of the surgeon, whose identity is a closely held secret. Someone else administers the drugs.

“The court is gravely concerned that a physician who is solely responsible for correctly mixing the drugs … has a condition which causes him confusion with regard to numbers,” Judge Gaitan wrote.

Judge Gaitan said a board-certified anesthesiologist must be responsible for mixing the drugs, and must either administer the drugs intravenously or directly observe those who do. The anesthesiologist must ensure the inmate has achieved “sufficient anesthetic depth” before receiving the final two drugs, which paralyze the inmate and stop the inmate’s heart. The heart-stopping drug, potassium chloride, causes excruciating pain.

It wasn’t clear whether the state would appeal the decision.

Mr. Crawford did not immediately return a phone call seeking comment. A spokesman for the attorney general said his office would have no comment before it discussed the matter with corrections officials.

A lawyer for Taylor, who won a stay in February hours before his execution had been scheduled, said his legal team was encouraged.

“We believe it’s a significant step toward remedying some of the very serious defects in Missouri’s lethal injection procedure,” Eric Berger said.