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GLOSSIP v. GROSS SOTOMAYOR, J., dissenting

function, they do so in a materially different way. Id., at 207. More specifically, Dr. Lubarsky explained that both barbiturates and benzodiazepines initially cause sedation by facilitating the binding of a naturally occurring chemi­ cal called gamma-aminobutyric acid (GABA) with GABA receptors, which then impedes the flow of electrical im­ pulses through the neurons in the central nervous system. Id., at 206. But at higher doses, barbiturates also act as a GABA substitute and mimic its neuron-suppressing ef­ fects. Ibid. By contrast, benzodiazepines lack this mim­ icking function, which means their effect is capped at a lower level of sedation. Ibid. Critically, according to Dr. Lubarsky, this ceiling on midazolam’s sedative effect is reached before full anesthesia can be achieved. Ibid. Thus, in his view, while “midazolam unconsciousness is .. . sufficient” for “minor procedure[s],” Tr. of Preliminary Injunction Hearing 132–133 (Tr.), it is incapable of keep­ ing someone “insensate and immobile in the face of [more] noxious stimuli,” including the extreme pain and discom­ fort associated with administration of the second and third drugs in Oklahoma’s lethal injection protocol, App. 218. Dr. Sasich endorsed Dr. Lubarsky’s description of the ceiling effect, and offered similar reasons for reaching the same conclusion. See id., at 243, 248, 262. In support of these assertions, both experts cited a variety of evidence. Dr. Lubarsky emphasized, in particu­ lar, Arizona’s 2014 execution of Joseph Wood, which had been conducted using midazolam and the drug hydromor­ phone rather than the three-drug cocktail Oklahoma intends to employ.1 Id., at 176. Despite being adminis­ tered 750 milligrams of midazolam, Wood had continued breathing and moving for nearly two hours—which, ac­ —————— 1 Hydromorphone is a powerful analgesic similar to morphine or hero­ in. See R. Stoelting & S. Hillier, Pharmacology & Physiology in Anes­ thetic Practice 87–88 (4th ed. 2006) (Stoelting & Hillier).