No. 14-7955
IN THE

Supreme Court of the United States
RICHARD E. GLOSSIP, et al.,

Petitioners,
v.
KEVIN J. GROSS,

Respondent.
ON WRIT OF CERTIORARI TO THE UNITED STATES
COURT OF APPEALS FOR THE TENTH CIRCUIT
BRIEF OF SIXTEEN PROFESSORS OF
PHARMACOLOGY AS AMICI CURIAE
IN SUPPORT OF NEITHER PARTY

JAMES K. STRONSKI

Counsel of Record
HARRY P. COHEN
CHIEMI D. SUZUKI
CROWELL & MORING LLP
590 Madison Avenue, 20th Fl.
New York, NY 10022-2524
(212) 223-4000
jstronski@crowell.com

Counsel for Amici Curiae

 i
TABLE OF CONTENTS

Page
Statement of Interest of Amici Curiae ....................... 1
Summary of Argument................................................ 8
Argument ..................................................................... 9
I.

Background ....................................................... 9

II.

Midazolam Is a Fast-Acting
Benzodiazepine that Produces
Reliable Hypnosis, Amnesia, and
Anti-anxiety Effects ........................................ 10

III.

Midazolam Is Incapable of
Rendering an Individual
Unconscious .................................................... 11
A.

Background on
Neurotransmission and
Neuronal Inhibition ............................. 11

B.

Midazolam Promotes CNS
Depression Only in the
Presence of GABA by
Increasing the Frequency of Ion
Channel Opening ................................. 13

C.

Barbiturates Depress the CNS
by Increasing the Duration of
Ion Channel Opening Even in
the Absence of GABA ........................... 16

 ii
D.

Because Midazolam Requires
Co-Binding of GABA and the
Amount of GABA is Limited,
Midazolam Cannot Overcome
Sub-Anesthetic Levels To
Provide General Anesthesia ................ 17

Conclusion ................................................................. 20

 iii
TABLE OF CITED AUTH
AUTHORITIES

Page
CASES

Warner v. Gross,
776 F.3d 721 (10th Cir. 2015) .......... 8, 9, 11, 18
OTHER AUTHORITIES
Brett A. Cromer et al., Anxiety over

GABAA Receptor Structure
Relieved by AChBP, 27 Trends in
Biochemical Sciences 280 (2002).................... 15
Bruce Alberts et al., Membrane
Transport, in Essential Cell
Biology 371 (1998) .............................. 12, 13, 15
Carl J. Rogers et al., Benzodiazepine

and β-carboline Regulation of
Single GABAA Receptor Channels
of Mouse Spinal Neurones in
Culture, 475 Journal of
Physiology 69 (1994) ................................. 15, 19
Charlotte D’Hulst et al., The

Complexity of the GABAA
Receptor Shapes Unique
Pharmacological Profiles,
14 Drug Discovery Today 866
(2009)................................................... 14, 15, 18

 iv
David A. Mathers & Jeffrey L. Barker,

(−)-Pentobarbital Opens Ion
Channels of Long Duration in
Cultured Mouse Spinal Neurons,
209 Science 507 (1980) ................................... 17
Dennis S. Charney et al., Hypnotics and
Sedatives, in Goodman &

Gilman’s The Pharmacological
Basis of Therapeutics 401 (James
F. Shanahan et al. eds., 11th ed.
2006) ........................................................ passim
Erwin Sigel & Michael E. Steinmann,

Structure, Function, and
Modulation of GABAA Receptors,
287 Journal of Biological
Chemistry 40224 (2012) ..................... 14, 15, 19
Feyza Sancar & Cynthia Czajkowski,

Allosteric Modulators Induce
Distinct Movements at the
GABA-binding Site Interface of
the GABA-A Receptor, 60
Neuropharmacology 520 (2011) .....................17
George M. Brenner & Craig W. Stevens,

Sedative-Hypnotic and Anxiolytic
Drugs, in Pharmacology 186 (4th
ed. 2013) .............................................. 18, 19, 20
Ismar Newton Cestari et al., The

Agonistic Action of Pentobarbital
on GABAA β-subunit Homomeric
Receptors, 7 NeuroReport 943
(1996)............................................................... 16

 v
J.G. Reves et al., Midazolam:

Pharmacology and Uses, 62
Anesthesiology 310 (1985) ............ 10, 11, 13, 20
L. John Greenfield Jr., Molecular

Mechanisms of Antiseizure Drug
Activity at GABAA Receptors, 22
Seizure 589 (2013) .................................... 13, 16
M. Ernst et al., Comparative Modeling

of GABAA Receptors: Limits,
Insights, Future Developments,
119 Neuroscience 933 (2003) .......................... 15
Meyer B. Jackson et al., Single Channel

Currents Activated by γaminobutyric Acid, Muscimol,
and (−)-Pentobarbital in Cultured
Mouse Spinal Neurons, 2 The
Journal of Neuroscience 889
(1982)............................................................... 17
Richard W. Olsen & Adele M.
Snowman, Chlorine-Dependent

Enhancement by Barbiturates of
γ-aminobutyric Acid Receptor
Binding, 2 The Journal of
Neuroscience 1812 (1982)............................... 16

 vi
Robert E. Study & Jeffrey L. Barker,

Diazepam and (−)-Pentobarbital:
Fluctuation Analysis Reveals
Different Mechanisms for
Potentiation of γ-aminobutyric
Acid Responses in Cultured
Central Neurons, 78 Proceedings
of the National Academy of
Sciences USA 7180 (1981) .................. 15, 16, 19
Robert L. Macdonald et al., Barbiturate

Regulation of Kinetic Properties
of the GABAA Receptor Channel
of Mouse Spinal Neurones in
Culture, 417 Journal of
Physiology 483 (1989) ..................................... 17
Trevor J. Anthony & Walter L. Way,
Sedative-Hypnotic Drugs, in

Basic & Clinical Pharmacology
379 (Bertram G. Katzung et al.
eds., 12th ed. 2012) ......................................... 18
Werner Sieghart et al., A Novel GABAA

Receptor Pharmacology: Drugs
Interfacing with the α+β−
Interface, 166 British Journal of
Pharmacology 476 (2012) ............................... 14
Werner Sieghart, Allosteric Modulation

of GABAA Receptors via Multiple
Drug-Binding Sites, 72 Advances
in Pharmacology 53 (2015) ............................. 14

 1
STATEMENT OF INTEREST
INTEREST OF AMICI CURIAE

Amici curiae, each of whom is listed below, are
professors of pharmacology at universities in the
United States.1 Amici curiae respectfully submit this
brief to provide a pharmacological perspective on the
physiologic effect of midazolam hydrochloride
(“midazolam”). Midazolam is a sedative in the
benzodiazepine class of drugs that the State of
Oklahoma decided to use in early 2014 as a
substitute for sodium thiopental (“thiopental”) and
pentobarbital as the first drug in the State’s threedrug lethal injection protocol. Amici curiae have no
interest in any party to this litigation, nor any stake
in the outcome of this case.2
Edward Bilsky, Ph.D. is the Vice President for
Research and Scholarship and a Professor of
Pharmacology at the University of New England in
Biddeford, ME. At the University of New England,
Dr. Bilsky is also the Founding Director of the
Center for Excellence in the Neurosciences. Dr.
Bilsky received a B.S. in Physics from Rensselaer
Polytechnic Institute in Troy, NY; a M.S. in
Behavioral
Neuroscience
from
Rensselaer
1 No counsel for a party authored this brief in whole or in
part, and no such counsel or party made a monetary
contribution intended to fund the preparation or submission of
this brief. No person other than the amici, or their counsel,
made a monetary contribution intended to fund its preparation
or submission. The parties have filed blanket waivers with the
Court consenting to the submission of all amicus briefs.
2 Each amicus curiae submits this brief in his or her
individual capacity. All of the institutional, organizational, and
professional affiliations noted in this section are for
identification purposes only.

 2
Polytechnic Institute in Troy, NY; and a Ph.D. in
Pharmacology and Toxicology from the University of
Arizona in Tucson, AZ. Dr. Bilsky was a PostDoctoral Research Fellow in Neuroscience at the
University of Arizona.
Charles Chavkin, Ph.D. is the Allan and
Phyllis Treuer Professor of Pharmacology at the
University of Washington in Seattle, WA. At the
University of Washington, Dr. Chavkin is also a
Professor in the Department of Pharmacology, the
Director of the Center for Drug Addiction Research,
and a Member of the Pharmacology, Neurobiology &
Behavior and Molecular & Cell Biology Graduate
Training Programs. Dr. Chavkin received a B.A. in
Biology from Cornell University in Ithaca, NY; and a
Ph.D. in Pharmacology from Stanford University in
Stanford, CA. Dr. Chavkin completed his postdoctoral training at the Salk Institute in La Jolla,
CA and Scripps Clinic in San Diego, CA.
Kathryn A. Cunningham, Ph.D. is the
Chauncey Leake Distinguished Professor of
Pharmacology, Vice Chairman of the Department of
Pharmacology and Toxicology, and the Director of
the Center of Addiction Research at the University of
Texas Medical Branch in Galveston, TX.
Dr.
Cunningham received a B.A. in Psychology and
Philosophy from the University of St. Thomas in
Houston, TX; and a Ph.D. in Experimental
Psychology (Behavioral Neuropharmacology) from
the University of South Carolina in Columbia, SC.
She completed a Post-Doctoral Fellowship in the
Department of Pharmacology and Toxicology at the

 3
University of Texas Medical Branch in Galveston,
TX.
Kenneth E. McCarson, Ph.D. is an Associate
Professor in the Department of Pharmacology,
Toxicology, and Therapeutics at the University of
Kansas Medical Center in Kansas City, KS. Dr.
McCarson received a B.Ch.E. in Chemical
Engineering from the Georgia Institute of
Technology in Atlanta, GA; and a Ph.D. in
Pharmacology, with distinction, from the Medical
College of Georgia in Augusta, GA. Dr. McCarson
was a Post-Doctoral Research Associate in
Neurobiology at the Washington University School of
Medicine in St. Louis, MO.
Christopher R. McCurdy, Ph.D. is a Professor
of Medicinal Chemistry and Pharmacology, and a
Research Professor in the Research Institute of
Pharmaceutical Sciences at the University of
Mississippi in University, MS.
Dr. McCurdy
received a B.S. in Pharmacy from Ohio Northern
University in Ada, OH; and a Ph.D. in Medicinal
Chemistry from the University of Georgia in Athens,
GA.
Dr. McCurdy completed a Post-Doctoral
Research Fellowship in Medicinal Chemistry at the
University of Minnesota in Minneapolis, MN.
Jay McLaughlin, Ph.D. is an Associate
Member of Pharmacology and Neuroscience at the
Torrey Pines Institute for Molecular Studies in Port
St. Lucie, FL. Dr. McLaughlin received a B.A. in
Biology from the University of California at Santa
Cruz in Santa Cruz, CA; a M.S. in Neuroscience from
the University of Rochester, School of Medicine and
Dentistry in Rochester, NY; and a Ph.D. in

 4
Neuroscience from the University of Rochester,
School of Medicine and Dentistry in Rochester, NY.
Dr. McLaughlin completed Post-Doctoral Research
Fellowships at the University of Rochester in
Rochester, NY, and at the University of Washington
in Seattle, WA.
S. Stevens Negus, Ph.D. is a Professor of
Pharmacology in the Department of Pharmacology
and
Toxicology
at
Virginia
Commonwealth
University in Richmond, VA. Dr. Negus received a
B.A. in English from the University of Virginia in
Charlottesville, VA; and a Ph.D. in Neurobiology
from the University of North Carolina in Chapel Hill,
NC.
Dr. Negus completed a Post-Doctoral
Fellowship at the Scripps Research Institute in La
Jolla, CA, and served on faculties at the University
of Michigan in Ann Arbor, MI, and Harvard Medical
School in Boston, MA.
Dennis J. Paul, Ph.D. is a Professor of
Pharmacology in the Department of Pharmacology
and Experimental Therapeutics at the Louisiana
State University School of Medicine in New Orleans,
LA.
Dr. Paul received a B.A., cum laude, in
Physiologic Psychology from the University of
Cincinnati in Cincinnati, OH; a M.A. in
Biopsychology from the University of British
Columbia in Vancouver, BC; and a Ph.D. in
Biopsychology from the University of British
Columbia in Vancouver, BC. Dr. Paul was a PostDoctoral Fellow in the Cotzias Laboratory for NeuroOncology at Memorial Sloan-Kettering Cancer
Center in New York, NY.

 5
Frank Porreca, Ph.D. is a Professor of
Pharmacology and Anesthesiology at the University
of Arizona College of Medicine in Tucson, AZ. Dr.
Porreca received a B.S. in General Sciences, with
honors, from Villanova University in Villanova, PA;
a M.S. in Biomedical Engineering from Drexel
University in Philadelphia, PA; and a Ph.D. in
Pharmacology
from
Temple
University
in
Philadelphia, PA. Dr. Porreca completed his postdoctoral
research
in
the
Department
of
Pharmacology at the University of Arizona in
Tucson, AZ.
Paul L. Prather, Ph.D. is a Professor of
Pharmacology in the Department of Pharmacology
and Toxicology at the University of Arkansas for
Medical Sciences in Little Rock, AR. Dr. Prather
received a B.S. in Pharmacy from Southwestern
Oklahoma State University in Weatherford, OK; and
a Ph.D. in Pharmacology from the University of
Georgia College of Pharmacy in Athens, GA. Dr.
Prather completed his post-doctoral research in the
Department of Pharmacology at University of North
Texas Health Science Center in Fort Worth, TX, and
in the Department of Pharmacology at the
University of Minnesota School of Medicine in
Minneapolis, MN.
Sandra C. Roerig, Ph.D. is a Professor in the
Department of Pharmacology, Toxicology and
Neuroscience; Dean of Graduate Studies; and
Associate Dean of Research at Louisiana State
University Health Sciences Center in Shreveport,
LA. Dr. Roerig received a B.S. in Horticulture from
Kansas State University in Manhattan, KS; and a

 6
Ph.D. in Pharmacology from the Medical College of
Wisconsin in Milwaukee, WI. Dr. Roerig completed
her post-doctoral research in the Department of
Pharmacology at the University of Minnesota in
Minneapolis, MN.
Kelly M. Standifer, Ph.D. is a Professor of
Pharmacology and Chair of the Department of
Pharmaceutical Sciences at the University of
Oklahoma College of Pharmacy in Oklahoma City,
OK. Dr. Standifer received an A.S. in Natural
Sciences from St. Gregory’s College in Shawnee, OK;
a B.S. in Zoology from Duke University in Durham,
NC; and a Ph.D. in Pharmacology from the
University of Florida in Gainesville, FL.
Dr.
Standifer was a Post-Doctoral Fellow in the
Molecular Pharmacology and Therapeutics Program
at Memorial Sloan-Kettering Cancer Center in New
York, NY.
John R. Traynor, Ph.D. is a Professor of
Pharmacology and Chair of the Pharmacology
Graduate Program at the University of Michigan
Medical School in Ann Arbor, MI. Dr. Traynor
received a B.S. in Pharmacy from the University of
Aston in the U.K.; and a Ph.D. in Medicinal
Chemistry from the University of Aston in the U.K.
Dr. Traynor’s post-doctoral research focused on
Biochemical Pharmacology at the University of
Gottingen in Germany.
Ellen Unterwald, Ph.D. is a Professor of
Pharmacology and Director of the Center for
Substance Abuse Research at Temple University
School of Medicine in Philadelphia, PA.
Dr.
Unterwald received a B.S. in Pharmacy from the

 7
University of Rhode Island in Kingston, RI; and a
Ph.D. in Pharmacology from Boston University
School of Medicine in Boston, MA. Dr. Unterwald
was a Post-Doctoral Fellow in the Department of
Neuroscience at Albert Einstein College of Medicine
in Bronx, NY.
David R. Wallace, Ph.D. is a Professor of
Pharmacology in the Department of Pharmacology
and Physiology, a former Assistant Dean for
Research, and Director for Integrative Neuroscience
at the Oklahoma State University Center for Health
Sciences in Tulsa, OK. Dr. Wallace received a B.S. in
Biomedical Science from Western Michigan
University in Kalamazoo, MI; and a Ph.D. in
Pharmaceutical Science from the University of
Florida in Gainesville, FL. Dr. Wallace completed
Post-Doctoral Fellowships in Pharmacology at the
University of Colorado Health Science Center in
Denver, CO, and in Pharmacology at the University
of Kentucky in Lexington, KY.
Linda Werling, Ph.D. is the Associate Dean for
Graduate Education, Director of the Institute for
Biomedical Sciences, Professor of Pharmacology and
Physiology, and Professor of Neurological Surgery at
the George Washington University School of
Medicine and Health Sciences in Washington, DC.
Dr. Werling received a B.S. in Biological Sciences
from Indiana University in Bloomington, IN; and a
Ph.D. in Pharmacology from Duke University in
Durham, NC. Dr. Werling was a Post-Doctoral
Fellow in the Department of Pharmacology at the
Uniformed Services University of the Health
Sciences in Bethesda, MD.

 8
Letters from the parties consenting to the
filing of amicus curiae briefs, in support of either
party or neither party, have been filed with the Clerk
of the Court.
SUMMARY OF ARGUMENT
The first drug in the State of Oklahoma’s
three-drug lethal injection protocol is intended to
ensure an inmate is in a “deep, comalike
unconsciousness” prior to the injection of a paralytic
agent to stop respiration, and a drug that induces
cardiac arrest. Warner v. Gross, 776 F.3d 721, 72425 (10th Cir. 2015), cert. granted, 135 S. Ct. 1173
(2015). Since early 2014, the State of Oklahoma has
used midazolam as the first drug in this sequence.
From a pharmacological perspective, however,
midazolam is not appropriate for its intended
purpose.
There is overwhelming scientific consensus,
including among pharmacologists, that midazolam is
incapable
of
inducing
a
“deep,
comalike
unconsciousness,” id. The biochemical interaction by
which midazolam produces its pharmacological effect
on the human body (i.e., its mechanism of action)
requires co-binding of a neurotransmitter, known as
γ-aminobutyric acid (“GABA”), and midazolam to
depress the activity of the central nervous system
(“CNS”). But the depth of that depression is limited,
and even an excessive dose of midazolam will not
result in unconsciousness.

 9
ARGUMENT
I.

Background

Before the Director of Oklahoma’s Department
of Corrections selected midazolam for use as the first
drug in the three-drug lethal injection protocol in
early 2014, the State of Oklahoma used drugs in the
barbiturate class known to “induce[] a deep, comalike
unconsciousness when given in the amounts used for
lethal injection.” Id. at 724-25 (citing Baze v. Rees,
553 U.S. 35, 44 (2008)). Until approximately 2010,
the State of Oklahoma used thiopental, a member of
the barbiturate drug class, as the first drug. Id. at
725. Later, it substituted an alternative drug in the
same barbiturate class, pentobarbital, as the first
drug in the protocol. Id. But in 2014, the State of
Oklahoma elected to use midazolam in its place. Id.
Midazolam is not an appropriate substitute for
thiopental or pentobarbital as the first drug in the
State of Oklahoma’s three-drug lethal injection
protocol. Increasing doses of barbiturates, including
thiopental and pentobarbital, will induce sedation,
then sleepiness, then anesthesia, then coma, and
finally death. Midazolam, however, is not a member
of the barbiturate drug class. It is a benzodiazepine,
a separate class of drugs that does not exert its
pharmacological effect in the same manner as
barbiturates.
This pharmacological distinction
explains
why
midazolam
cannot
induce
unconsciousness at any dose, and why it is not an
appropriate substitute for either thiopental or
pentobarbital as the first drug in a three-drug lethal
injection protocol.

 10
II.

Midazolam Is a FastFast-Acting
Benzodiazepine that Produces Reliable
Hypnosis, Amnesia, and AntiAnti-anxiety
Effects

Midazolam was first synthesized in 1976 and
belongs to a class of drugs called benzodiazepines.
J.G. Reves et al., Midazolam: Pharmacology and
Uses, 62 Anesthesiology 310, 310 (1985).
Benzodiazepines are CNS depressants that reliably
provide sedative, hypnotic3, muscle relaxant, anxiety
inhibitory, and anticonvulsant effects. Dennis S.
Charney et al., Hypnotics and Sedatives, in

Goodman & Gilman’s The Pharmacological Basis of
Therapeutics 401, 410-11 (James F. Shanahan et al.
eds., 11th ed. 2006); Reves at 311-12. In addition to
midazolam, the benzodiazepine family also includes
the active pharmaceutical ingredients in XANAX®
(alprazolam), KLONOPIN® (clonazepam), VALIUM®
(diazepam), and ATIVAN® (lorazepam), among
others. Charney at 410-11.
Structurally speaking, midazolam differs from
other benzodiazepines in that it has a fused
imidazole ring, which confers unique physiochemical
properties, including basicity (as opposed to acidity),
stability in aqueous solution, and rapid metabolism
in the body. Reves at 310. At physiologic pH (i.e.,
pH of the blood), midazolam becomes highly
lipophilic (i.e., able to dissolve in fats), giving rise to
3 Hypnotic drugs “produce[] drowsiness and facilitate[] the
onset and maintenance of a state of sleep that resembles
natural sleep in its electroencephalographic characteristics and
from which the recipient can be aroused easily.” Charney at
401.

 11
various clinical consequences, including rapid entry
of midazolam into brain tissue and very rapid onset
of activity following intravenous administration. Id.
at 315. Although it is fast acting, midazolam also
has a short duration of activity due to its very high
metabolic clearance and rapid rate of elimination
from the body. Id. Termination of the clinical effect
following a single dose of midazolam is also rapid.

Id.
These properties make midazolam an
attractive choice as a pre-medication given prior to
the induction of anesthesia. Id. at 317-18. But while
midazolam produces sleep and amnesia, with a short
duration of activity, it cannot be used to render a
person unconscious or to maintain general
anesthesia. Id.
III.

Midazolam Is Incapable of Rendering
an Individual Unconscious

Midazolam’s mechanism of action differs from
barbiturates. This critical difference demonstrates
why midazolam cannot induce unconsciousness, and
why it is an improper substitute for thiopental or
pentobarbital as the first drug in the State of
Oklahoma’s three-drug lethal injection protocol.
A.

Background on Neurotransmission and
Neuronal Inhibition

To understand how midazolam works on the
body—and ultimately to convey why midazolam is
incapable of “render[ing] an inmate unconscious
prior to the injection of the second and third drugs,”
Warner, 776 F.3d at 725—requires some background

 12
on neurotransmission, the process by which neurons
(i.e., nerve cells) receive, conduct, and transmit
signals.
Neurotransmission is at the heart of every
action in our daily lives, taking a stimulus,
converting it into a nerve impulse, and resulting in
some action or inaction. When we touch a hot burner
on a stove, we immediately pull our hand away. In
the home, this is a clumsy kitchen mishap. But in
the classroom, this is a classic lesson in
neurotransmission.
At the biochemical level,
touching the hot burner stimulates heat and pain
receptors on the hand, which send nerve impulses to
the spinal cord. Those nerve impulses are then
transferred to neurons that are ultimately connected
to the muscles in the arm and hand that are
stimulated to contract to pull the hand away. This
cascade of events is the result of a series of
electrochemical
reactions
mediated
by
neurotransmitters. Neurotransmitters are chemicals
that bind to receptors, causing ion channels to open
or close, thus exciting or inhibiting individual
neurons.
GABA
is
the
major
inhibitory
neurotransmitter in the human body. E.g., Bruce
Alberts et al., Membrane Transport, in Essential Cell
Biology 371, 400-01 (1998); Charney at 405. When
inhibitory neurons of the brain release GABA onto
other brain neurons, GABA binds to GABA-specific
receptors. Alberts at 400-01. This binding causes
chloride ion channels to open on the recipient
neurons. Id. The influx of chloride ions through the
channel causes those neurons to become more

 13
quiescent, to decrease in electrical activity, and to
decrease the likelihood of neuronal firing. Id. at 401.
The result is neuronal inhibition and ultimately CNS
depression. Id.
By way of example, seizures result from a
failure of inhibitory neurotransmission, and there is
substantial
evidence
linking
epilepsy
with
dysfunction of GABA-specific neuronal inhibition. L.
John Greenfield Jr., Molecular Mechanisms of
Antiseizure Drug Activity at GABAA Receptors, 22
Seizure 589, 589 (2013). Drugs that block or dampen
GABA’s effect on binding to the GABA receptor are
called “antagonists.”
Id.
By preventing or
decreasing the likelihood of chloride ion influx
through the ion channel, these antagonists can
induce seizures. Id. Conversely, drugs that activate
the GABA receptor are called “agonists,” and by
increasing the frequency of ion channel opening, or
increasing the opening time of the ion channel to
longer durations, agonists work to sustain neuronal
inhibition and control seizures. Id. at 590-92. Even
outside of the context of seizures, pharmaceutically
promoting neuronal inhibition requires agonists that
enhance the chloride ion channel permeability of
GABA receptors. E.g., Alberts at 401.
B.

Midazolam Promotes CNS Depression
Only in the Presence of GABA by
Increasing
Increasing the Frequency of Ion
Channel Opening

Once in the body, midazolam, like all
benzodiazepines, acts by promoting the binding of
the neurotransmitter GABA to the GABAA receptor.
Charney at 402; Reves at 311-12; Greenfield at 591.

 14
GABAA receptors, a sub-type of GABA receptors, are
ion channels with multiple binding sites that can be
opened by GABA, but that also can be modulated by
drugs, including benzodiazepines. Werner Sieghart,

Allosteric Modulation of GABAA Receptors via
Multiple Drug-Binding Sites, 72 Advances in
Pharmacology 53, 54-55 (2015).
When midazolam alone binds to the GABAA
receptor,
there
is
no
inhibitory
neuronal
consequence. Erwin Sigel & Michael E. Steinmann,

Structure, Function, and Modulation of GABAA
Receptors, 287 Journal of Biological Chemistry
40224, 40227 (2012); Charlotte D’Hulst et al., The
Complexity of the GABAA Receptor Shapes Unique
Pharmacological Profiles, 14 Drug Discovery Today
866, 872 (2009); Charney at 405. In other words, the
binding of midazolam alone to the GABAA receptor
does not open the ion channel to allow for chloride
ion influx into the neuron. Rather, midazolam
requires the additional co-binding of GABA to the
GABAA receptor to exert an inhibitory effect.
D’Hulst at 872; Charney at 405-06; Werner Sieghart
et al., A Novel GABAA Receptor Pharmacology:
Drugs Interfacing with the α+β− Interface, 166
British Journal of Pharmacology 476, 476-77 (2012).
This requires coordination, as neuronal inhibition by
midazolam therefore requires GABA to be released
by inhibitory neurons and available to bind to the
GABAA receptor at the same time that the drug is
available to bind. D’Hulst at 872; Charney at 40506; Sieghart (2012) at 477.
Midazolam and GABA bind to the GABAA
receptor at distinct sites. Brett A. Cromer et al.,

 15

Anxiety over GABAA Receptor Structure Relieved by
AChBP, 27 Trends in Biochemical Sciences 280, 280
(2002); M. Ernst et al., Comparative Modeling of
GABAA Receptors: Limits, Insights, Future
Developments, 119 Neuroscience 933, 938-39 (2003).
When midazolam binds to the benzodiazepine site on
a GABAA receptor, this leads to a conformational
change of the receptor itself. Sigel & Steinmann at
40227.
The conformational change increases the
affinity of the GABA neurotransmitter to its own
GABAA receptor binding site. Id.; Charney at 406.
The increased affinity of GABA for the GABAA
receptor binding site means that in the presence of
bound midazolam, even sub-maximal amounts of
GABA will open the GABAA ion channel. Sigel &
Steinmann at 40227; Charney at 406.
The result of co-application of midazolam and
GABA to the GABAA receptor is an increase in the
frequency of chloride ion channel opening. Sigel &
Steinmann at 40228; Robert E. Study & Jeffrey L.
Barker, Diazepam and (−)-Pentobarbital: Fluctuation

Analysis Reveals Different Mechanisms for
Potentiation of γ-aminobutyric Acid Responses in
Cultured Central Neurons, 78 Proceedings of the
National Academy of Sciences USA 7180, 7183
(1981); Carl J. Rogers et al., Benzodiazepine and β-

carboline Regulation of Single GABAA Receptor
Channels of Mouse Spinal Neurones in Culture, 475
Journal of Physiology 69, 69, 72-73, 77, 79 (1994);
Charney at 406. The resultant influx of chloride ions
into the neuron suppresses neuronal firing, and
ultimately produces the hallmark sedative and
hypnotic effects of the drug. E.g., Alberts at 400-01;
D’Hulst at 866.

 16
By way of analogy, the GABAA receptor can be
thought of as a keyed gate through which chloride
ions can enter a neuron. GABA and midazolam are
keys to that gate. The GABA key alone opens the
gate, allowing for chloride ion influx. The midazolam
key alone does not open the gate, but simultaneous
use of the GABA and midazolam keys results in
increased frequency of gate opening, as compared to
the frequency of gate opening using the GABA key
alone.
C.

Barbiturates Depress the CNS by
Increasing the Duration of Ion Channel
Opening Even in the Absence of GABA

Barbiturates,
including
thiopental
and
pentobarbital, also act on the GABAA receptor. E.g.,
Richard W. Olsen & Adele M. Snowman, Chlorine-

Dependent Enhancement by Barbiturates of γaminobutyric Acid Receptor Binding, 2 The Journal
of Neuroscience 1812, 1812 (1982); Greenfield at 589;
Charney at 414-16. The binding site for barbiturates
is located in a different region of the GABAA
receptor, distinct from the binding site for
benzodiazepines. Ismar Newton Cestari et al., The

Agonistic Action of Pentobarbital on GABAA βsubunit Homomeric Receptors, 7 NeuroReport 943,
946 (1996); Charney at 414. While benzodiazepines
enhance GABA inhibition by modulating the
frequency of ion channel opening, barbiturates
enhance GABA inhibition by increasing the time the
ion channel remains open. Study & Barker at 718283; Charney at 406, 414.
Unlike benzodiazepines, which require the
presence of GABA to produce a pharmacologic effect,

 17
barbiturates confer neuronal inhibition even in the
absence of GABA. David A. Mathers & Jeffrey L.
Barker, (−)-Pentobarbital Opens Ion Channels of
Long Duration in Cultured Mouse Spinal Neurons,
209 Science 507, 507-08 (1980); Meyer B. Jackson et
al., Single Channel Currents Activated by γ-

aminobutyric Acid, Muscimol, and (−)-Pentobarbital
in Cultured Mouse Spinal Neurons, 2 The Journal of
Neuroscience 889, 890-93 (1982); Charney at 406.
Therefore, the binding of barbiturates to the GABAA
receptor opens the chloride ion channel in the
absence of GABA and keeps the channel open longer
than benzodiazepines. Robert L. Macdonald et al.,

Barbiturate Regulation of Kinetic Properties of the
GABAA Receptor Channel of Mouse Spinal Neurones
in Culture, 417 Journal of Physiology 483, 491-96
(1989);

Feyza

Sancar

&

Cynthia

Czajkowski,

Allosteric Modulators Induce Distinct Movements at
the GABA-binding Site Interface of the GABA-A
Receptor, 60 Neuropharmacology 520, 527 (2011);
Charney at 406, 414. In other words, even in the
absence of GABA, barbiturates can increase the
influx of chloride ions into the neuron to completely
shut down the activity of the neuron.
D.

Because Midazolam Requires CoCoBinding of GABA and the Amount of
GABA is Limited,
Limited, Midazolam Cannot
Overcome SubSub-Anesthetic
nesthetic Levels To
Provide General Anesthesia

As noted above, when a drug activates its
receptor, it is called an agonist. A drug that activates
its receptor to produce a maximal effect is called a
full agonist; one that cannot produce the maximal

 18
effect is called a partial agonist.
Because
benzodiazepines facilitate GABA actions, they are
considered agonists. E.g., Trevor J. Anthony &
Walter L. Way, Sedative-Hypnotic Drugs, in Basic &
Clinical Pharmacology 379, 379 (Bertram G.
Katzung et al. eds., 12th ed. 2012); D’Hulst at 872.
Yet because benzodiazepines require co-activation
with GABA to produce a pharmacologic effect, and
the amount of GABA is limited, they can produce
only a partial agonist effect. George M. Brenner &
Craig W. Stevens, Sedative-Hypnotic and Anxiolytic
Drugs, in Pharmacology 186, 192 (Fig. 19-3) (4th ed.
2013) Barbiturates, on the other hand, act to inhibit
neurons even in the absence of GABA and produce
full agonist effects. Id. Thus, midazolam is only a
partial agonist, and the depth of its inhibitory effect
has limits.
This difference between full agonist and
partial agonist explains why barbiturates like
thiopental and pentobarbital can induce a “deep,
comalike unconsciousness when given in the
amounts used for lethal injection,” Warner, 776 F.3d
at 724 (citing Baze, 553 U.S. at 44), and why
midazolam is incapable of “render[ing] an inmate
unconscious prior to the injection of the second and
third drugs,” id. at 725. This difference, referred to
as the “ceiling effect” of the benzodiazepine response,
is illustrated in the figure below.

 19

Brenner & Stevens at 192 (Fig. 19-3). As depicted
above, greater doses of benzodiazepines will not
produce greater pharmacological effects, while
greater doses of barbiturates will produce greater
pharmacological effects. See id. This is for two
reasons. First, benzodiazepines require the presence
of GABA to exert a pharmacological effect and
barbiturates do not. E.g., Charney at 405-06. Yet
GABA is present in limited supply in the CNS, and
the limited quantity of GABA restricts the
pharmacological effect of benzodiazepines. See, e.g.,
id. at 406. Second, benzodiazepines work differently.
Specifically, benzodiazepines merely increase the
frequency of ion channel opening when GABA is also
present. Sigel & Steinmann at 40228; Study &
Barker at 7183; Rogers at 69, 72-73, 77, 79; Charney
at 406. Unlike barbiturates, benzodiazepines do not
affect the duration of ion channel opening. E.g.,
Charney at 406.
With reference to the increasing CNS effects
on the vertical axis in the figure above, as the dose of
benzodiazepine increases, the benzodiazepine curve

 20
plateaus, reaching a “ceiling” before general
anesthesia can be obtained. See Brenner & Stevens
at 192 (Fig. 19-3).
Therefore, the response to
benzodiazepines cannot be further enhanced to
unconsciousness and beyond by increasing the dose.
See id. The fact that midazolam does not ever
achieve general anesthesia is consistent with and
explains the clinical uses of the drug. In fact, it is
widely recognized in the scientific and medical
community that midazolam alone cannot be used to
maintain adequate anesthesia for surgery. E.g.,
Reves at 318; Charney at 404 (“The clinical literature
often refers to the ‘anesthetic’ effects and uses of
certain benzodiazepines, but the drugs do not cause a
true general anesthesia because awareness usually
persists, and relaxation sufficient to allow surgery
cannot be achieved.”). By contrast, barbiturates do
not exhibit this ceiling effect.
See Brenner &
Stevens at 192 (Fig. 19-3). Accordingly, increasing
doses of barbiturates reliably produce anesthesia,
coma, and death. See id.
In sum, midazolam’s mechanism of action
makes it unsuitable as the first drug in the State of
Oklahoma’s three-drug lethal injection protocol
because it is incapable of inducing unconsciousness.
CONCLUSION
From
a
pharmacological
perspective,
midazolam is not interchangeable with barbiturates
like thiopental or pentobarbital.
Midazolam is
incapable of rendering an inmate unconscious prior
to the injection of the second and third drugs in the
State of Oklahoma’s lethal injection protocol.
Therefore, midazolam is not appropriate for its

 21
intended purpose as the first drug in the State of
Oklahoma’s three-drug lethal injection protocol.

Respectfully Submitted,

JAMES K. STRONSKI

Counsel of Record
HARRY P. COHEN
CHIEMI D. SUZUKI
CROWELL & MORING LLP
590 Madison Avenue, 20th Fl.
New York, NY 10022-2524
(212) 223-4000
jstronski@crowell.com

Counsel for Amici Curiae
March 16, 2015