F I L E D

United States Court of Appeals

Tenth Circuit

JUL 17 2001

PATRICK FISHER

Clerk

PUBLISH

UNITED STATES COURT OF APPEALS

TENTH CIRCUIT

MARK W. ECK, SANDRA K. ECK,

TRAVIS ECK and MEGAN ECK,

Plaintiffs-Appellants,

v. No. 00-7020

PARKE, DAVIS & COMPANY,

WARNER-LAMBERT COMPANY,

THE RUGBY GROUP, INC., AND

RUGBY LABORATORIES, INC., 

Defendants-Appellees.

Appeal from the United States District Court

for the E.D. Oklahoma

(D.C. NO. 99-CV-156-S)

Steven E. Aldous, Slack & Davis, L.L.P., Austin, Texas, for Appellants.

Brad Smith (Mike Barkley with him on the brief) of Barkley Titus Hillis &

Reynolds, Tulsa, Oklahoma, for Appellees Parke, Davis & Company and WarnerLambert Company.

Thomas E. Steichen (Richard M. Eldridge with him on the brief) of Rhodes,

Hieronymus, Jones, Tucker & Gable, P.L.L.C., Tulsa, Oklahoma, for Appellees

The Rugby Group, Inc. and Rugby Laboratories, Inc.
*

 The Honorable G. Thomas Van Bebber, United States Senior District

Judge for the District of Kansas, sitting by designation.

1

 Sandra Eck, the wife of Mark Eck, brought a claim for loss of spousal

consortium. Two of Mark Eck’s children, Travis and Megan Eck, brought claims

for loss of parental consortium.

2

 Plaintiffs also sued Hoechst Marion Roussel, Inc. and Watson

Pharmaceuticals, Inc., who were dismissed from this action by the district court.

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Before HENRY and MURPHY , Circuit Judges, and VAN BEBBER , District

Judge. *

HENRY, Circuit Judge.

Mark W. Eck, suffering from injuries sustained from an onset of liver

failure, brought, together with members of his family, this products liability

action 1

 against defendants Parke, Davis & Company and Warner-Lambert

Company (jointly, “Warner-Lambert”) and the Rugby Group, Inc. and Rugby

Laboratories, Inc. (jointly, “Rugby”). 2 The Ecks contended that Mr. Eck’s liver

failure resulted from the interaction of two prescription drugs: (1) Dilantin, an

anti-convulsant, which is manufactured and distributed by Warner-Lambert, and

(2) Isocet (which contains acetaminophen, butalbital and caffeine), and which is

distributed by Rugby. The defendants filed a motion for summary judgment in the

district court, which the district court granted. The district court found that the
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Ecks’ claims were barred by the learned intermediary doctrine. For the reasons

set forth below, we affirm the district court’s decision. We are called upon to

decide only the liability of these defendants; the liability of other actors is not

before us.

I. BACKGROUND

The following facts are undisputed. Mr. Eck is a pharmacist who owns and

operates Eck Pharmacy in Healdton, Oklahoma. In 1992 or 1993, Dr. Mark

Newey became Mr. Eck’s treating physician. On March 13, 1994 and on January

19, 1995, Dr. Newey prescribed Isocet to Mr. Eck to treat his complaints of

tension headaches. At the time the Isocet was prescribed by Dr. Newey, Mr. Eck

was not taking Dilantin.

Mr. Eck has a history of mild temporal lobe seizures. In October 1996, Dr.

Newey prescribed Tegretol, another anti-convulsant medication, after Mr. Eck

began to experience seizures. While on the Tegretol, Mr. Eck developed a rash

and Dr. Newey referred him in mid-December 1996 to Dr. Dan Udonta, who, in

turn, prescribed Depakote in lieu of the Tegretol. Mr. Eck again developed a

rash. On January 31, 1997, Dr. Udonta referred Mr. Eck to Dr. Nancy Rodgers,

an epilepsy specialist. 
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Five days later Mr. Eck experienced another seizure-related episode. Dr.

Newey came to Mr. Eck’s house and consulted with Dr. Rodgers via telephone.

Mr. Eck was admitted to the Healdton Hospital emergency room on February 5,

1997. Dr. Newey ordered a 900 mg loading dose of Dilantin that was given to

Mr. Eck. He was discharged on February 6, 1997, and sent by Dr. Newey to see

Dr. Rodgers. Thereafter, Dr. Rodgers removed Mr. Eck from the Depakote and

prescribed Dilantin to control his seizures. Dr. Newey monitored his Dilantin

levels during the time Dr. Rodgers prescribed Dilantin.

On April 5, 1997, Mr. Eck began to feel anxious. On April 7, 1997, he

began experiencing a tension headache and took two Isocet tablets (each

containing 325 mg of acetaminophen) from his January 19, 1995 prescription. 

During this period of time, Mr. Eck was also taking Dilantin, prescribed in

February by Dr. Rodgers to control his seizures. He had taken 400 mg of Dilantin

that day.

On April 8, 1997, Mr. Eck began vomiting repeatedly and his condition

continued to deteriorate. Dr. Newey admitted him to Mercy Hospital in Ardmore,

Oklahoma. At Mercy Hospital, Mr. Eck was diagnosed with acute liver failure

and he was transported to Baylor Medical Center in Dallas, Texas. A liver biopsy

revealed that Mr. Eck’s liver failure was consistent with acetaminophen

poisoning. As a result of his liver failure and related complications, Mr. Eck was
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in a coma and on a ventilator for 36 days. He underwent various surgeries and

had an extended hospital stay.

In granting the defendants’ motion for summary judgment, the district court

found that Oklahoma’s “learned intermediary doctrine” shielded Warner-Lambert

and Rugby from liability because any failure to warn was not the proximate cause

of Mr. Eck’s injuries. The district court found summary judgment inappropriate

with respect to the two related grounds of (1) no duty to warn when there is no

known danger of the interaction of the drugs at therapeutic levels, and (2) the

absence of medical causation. Because we affirm for the reasons given below, we

need not address the appropriateness of the denial of summary judgment on these

grounds.

On appeal, the Ecks challenge: (1) the district court’s decision to limit its

focus of inquiry to the testimony of Dr. Rodgers, the physician who prescribed

Dilantin, and not to consider the testimony of Dr. Newey, the prescribing

physician for Isocet; (2) the district court’s conclusion that Dr. Rodgers’

testimony rebutted the presumption that had an adequate warning been provided,

it would have been read and heeded; and (3) the district court’s finding that no

issues of material fact regarding causation existed. After we review the

progression and rationale of the learned intermediary doctrine, we shall discuss

each contention in turn.
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II. INITIAL MATTERS

A. Standard of Review

This diversity action is governed by Oklahoma’s substantive tort law, but

we are governed by federal law in determining the propriety of the district court’s

grant of summary judgment. See Pegasus Helicopters, Inc. v. United Techs.

Corp. , 35 F.3d 507, 510 (10th Cir. 1994). “We review the entry of summary

judgment de novo, drawing all reasonable inferences in favor of the nonmovants. 

Summary judgment is appropriate only when the moving party shows there is no

genuine issue as to any material fact and that the moving party is entitled to a

judgment as a matter of law. To avoid summary judgment, the nonmovant must

make a showing sufficient to establish an inference of the existence of each

element essential to the case. The nonmovant may not rest upon mere allegation

or denials of his pleadings, but must set forth specific facts showing that there is

a genuine issue for trial.” Hulsey v. Kmart, Inc. , 43 F.3d 555, 557 (10th Cir.

1994) (quotations and citations omitted).

B. Failure to Warn and the Learned Intermediary Doctrine

The Ecks contend that Warner-Lambert and Rugby, by failing to label their

products with adequate warnings of Dilantin’s propensity to interact with
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acetaminophen, placed defective and unreasonably dangerous products in the

market place that caused Mr. Eck’s liver failure. The Ecks also contend the

defendants were negligent in the designing, testing, warning, and marketing of

their products through their failure to provide adequate instructions or warnings

and by misrepresenting the safety of their products when used in conjunction with

one another.

To recover in a failure to warn case, a plaintiff must establish both causein-fact (that the product in question caused the injury) and proximate cause (that

the manufacturer of the product “breached a duty to warn of possible detrimental

reactions”). McKee v. Moore , 648 P.2d 21, 23-24 (Okla. 1982). To qualify as a

proximate cause of the injury, the breach of a duty or failure to warn must be a

substantial contributing factor in bringing about the harm in question. See

Woolard v. JLG Indus. Inc. , 210 F.3d 1158, 1172 (10th Cir. 2000) (applying

Oklahoma law) (noting that “a proximate cause is defined as one that, in the

natural and continuous sequence, produces the plaintiff’s injury and without

which the injury would not have happened”); Van Buskirk v. Carey Canadian

Mines, Ltd. , 760 F.2d 481, 492 (3d Cir. 1985) (applying Pennsylvania law)

(internal quotation marks omitted).

Oklahoma’s products liability law “generally requires a manufacturer to

warn consumers of danger associated with the use of its product to the extent the
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manufacturer knew or should have known of the danger.” Edwards v. Basel

Pharms. , 933 P.2d 298, 300 (Okla. 1997). Certain products, including

prescription drugs, are “unavoidably unsafe products” that cannot be made

completely safe, but serve a public benefit. See id. ; Restatement (Second) Torts §

402A cmt. k (1965) (the “Restatement”). Oklahoma law recognizes that drug

manufacturers cannot be strictly liable merely because of the dangerous

propensities of such products. See Edwards , 933 P.2d at 300. Such products, if

“properly prepared, and accompanied by proper directions and warning[s, are] not

defective, nor [are they] unreasonably dangerous.” Restatement § 402A cmt. k;

Edwards , 933 P.2d at 300 (stating that “the law regarding such products appears

at Comment k of the Restatement”).

Relying on Comment k, the Edwards court noted the exception to the

manufacturer’s duty to warn the ultimate consumer known as the “learned

intermediary doctrine”: where a product is properly prepared and marketed and

proper warning is given to the prescribing physicians, the manufacturer is

shielded from liability. Edwards , 933 P.2d at 300. “The reasoning behind this

rule is that the doctor acts as a learned intermediary between the patient and the

prescription drug manufacturer by assessing the medical risks in light of the

patient’s needs.” Id. 

The Edwards court adopted the rationale cited by the Kansas Supreme Court
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when it adopted the learned intermediary doctrine:

Where a product is available only on prescription or through the

services of a physician, the physician acts as a ‘learned intermediary’

between the manufacturer or seller and the patient. It is his duty to

inform himself of the qualities and characteristics of those products

which he prescribes for or administers to or uses on his patients, and to

exercise independent judgment, taking into account his knowledge of

the patient as well as the product. The patient is expected to and, it

can be presumed, does place primary reliance upon that judgment. The

physician decides what facts should be told to the patient. Thus, if the

product is properly labeled and carries the necessary instructions and

warnings to fully apprize the physician of the proper procedures for use

and the dangers involved, the manufacturer may reasonably assume that

the physician will exercise the informed judgment thereby gained in

conjunction with his own independent learning, in the best interest of

the patient.

Edwards , 833 P.2d at 300-01 (emphasis added) (quoting Wooderson v. Ortho

Pharm. Corp. , 681 P.2d 1038, 1052 (1984) (applying Kansas law)). This rationale

applies to prescription drugs, because “the patient may obtain the drug only

through a physician’s prescription, and the use of prescription drugs is generally

monitored by a physician.” Id. at 301; see also Garside v. Osco Drug, Inc. , 976

F.2d 77, 80 (1st Cir. 1992) (applying Massachusetts law) (“The rationale

underlying the [learned intermediary doctrine] is that the prescribing physician, as

the ‘learned intermediary’ standing between the manufacturer and

consumer/patient, is generally in the best position to evaluate the potential risks

and benefits of ingesting a certain drug and to advise the patient accordingly. 
-10-

Under this doctrine, the manufacturer’s duty is fulfilled once it adequately warns

the physician.”). 

Thus, in this case, the Ecks contend that Warner-Lambert had a duty to

adequately warn Dr. Rodgers, the prescribing physician, and Rugby had a duty to

adequately warn Dr. Newey, the treating physician, of the qualities and

characteristics of Dilantin and acetaminophen and of potential risks associated

with their concomitant use.

C. The Rebuttable Presumption under the Learned Intermediary Doctrine

Under Oklahoma law, the Ecks benefit from the development of a

rebuttable presumption in their favor:

[w]here a consumer, whose injury the manufacturer should have

reasonably foreseen, is injured by a product sold without a required

warning, a rebuttable presumption will arise that the consumer would

have read any warning provided by the manufacturer, and acted so as to

minimize the risks.

Cunningham v. Charles Pfizer & Co. , 532 P.2d 1377, 1382 (Okla. 1974)

(emphasis added) (quoting Reyes v. Wyeth Labs. , 498 F.2d 1264, 1281 (5th Cir.

1974) (applying Texas law)). The manufacturer warns the consumer, who is the

prescribing physician, who, in turn, acts as the learned intermediary. See Woulfe

v. Eli Lilly & Co. , 965 F. Supp. 1478, 1483 (E.D. Okla. 1997) (stating the
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Cunningham rebuttable “presumption . . . applies equally to the situation of

learned intermediaries”). 

“In the duty to warn context, assuming that plaintiffs have established both

duty and a failure to warn, plaintiffs must further establish proximate causation by

showing that had defendant issued a proper warning to the learned intermediary,

he would have altered his behavior and the injury would have been avoided.” 

Mazur v. Merck & Co. , 742 F. Supp. 239, 262 (E.D. Pa. 1990); see Thomas v.

Hoffman-LaRoche, Inc. , 949 F.2d 806, 812 (5th Cir. 1992) (applying Mississippi

law) (stating that “to create a jury question, the evidence introduced must be of

sufficient weight to establish, by the preponderance of the evidence, at least some

reasonable likelihood that an adequate warning would have prevented the plaintiff

from receiving the drug”). To inform the prescribing physicians of the potential

risks of an interaction during the concomitant use of acetaminophen and Dilantin,

Mr. Eck proposed that the following warning should have been included on both

products:

Phenytoin (generic name for Dilantin) may enhance the hepatoxicity

of acetaminophen secondary to enzyme induction and glutathione

depletion. Patients are advised to avoid concomitant use of

acetaminophen and phenytoin. 

Aplt’s App. vol. III, doc. 31, at 2 (Dist. Ct. Order filed Jan. 18, 2000).

 The district court apparently assumed without deciding that the Ecks

demonstrated that the manufacturer failed to warn of a non-obvious risk about
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which it knew or should have known, pursuant to Cunningham . Because the

adequacy of the proposed warning is irrelevant in light of Dr. Rogers’ testimony

discussed infra , we assume, for the limited purposes of this appeal, that the Ecks

are correct in their assertion that the defendants failed to warn the prescribing

physician of this risk. The Ecks thus receive the benefit of a rebuttable

presumption that an adequate warning “would have been read and heeded.” 

Woulfe , 965 F. Supp. at 1483; cf. Van Buskirk , 760 F.2d at 493 (noting that

defendant may “defeat causation in a failure to warn case by discrediting

plaintiffs’ claims that . . . [the learned intermediary] . . . would have acted to

avoid” the injury).

 Having established the presumption of causation-in-fact in the Ecks’ favor,

we must next determine whether the defendants, through the testimony of Drs.

Rodgers and Newey, have rebutted this presumption. The defendants may rebut

this presumption by establishing that although the prescribing physician would

have “read and heeded” the warning or additional information, this would not

have changed the prescribing physician’s course of treatment. See Woulfe , 965 F.

Supp. at 1485. The weight we afford to the physicians’ “testimony . . . depends

on the substance of the evidence as well as the credibility and reliability of the

treating physician[s].” Id.
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Assuming the defendants successfully rebut this presumption, the burden

shifts rather heavily back upon the Ecks. Our inquiry looks to whether the Ecks

“[came] forward with evidence sufficient to submit the case to a jury to determine

if [defendants’] alleged inadequate warning[s]” were a proximate cause of Mr.

Eck’s injuries. Id. at 1483; see also Garside , 976 F.2d at 81 (noting that “once

the presumption is rebutted, plaintiff must produce sufficient evidence to create a

triable issue on the question of causation”). To submit the case to a jury, the Ecks

must either discredit the physicians’ testimony or call into question the substance

of the testimony, or otherwise demonstrate that the alleged failure to warn was the

proximate cause of their injuries. Such a showing requires that the plaintiff 

“demonstrate that the additional non-disclosed risk was sufficiently high that it

would have changed the treating physician’s decision to prescribe the product for

the plaintiff.” Thomas , 949 F.2d at 813 (applying Mississippi law); see also

Woulfe , 965 F. Supp. at 1485-86; In re Norplant Contraceptive Prods. Liability

Litig. , 955 F. Supp. 700, 710 (E.D. Tex. 1997) (where physician was aware of

dangers associated with drug and information that would have been provided in

warning would not have changed his decision to prescribe drug, court held no

causation), aff’d , 165 F.3d 374 (5th Cir. 1999). 

III. DISCUSSION
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The Ecks contend that the district court made several errors when it granted

summary judgment to the defendants. First, they challenge the court’s decision to

focus primarily on the testimony given by Dr. Rodgers rather than also looking at

the testimony given by Dr. Newey. Second, they dispute that Dr. Rodgers’

testimony rebuts the presumption that she would have read and heeded a warning

about the interaction of Dilantin and acetaminophen. They also suggest that

because her testimony did not unequivocally indicate she had substantially the

same knowledge of the adverse risks that their proposed warnings would have

imparted, she could not properly evaluate the risks of the drugs’ interaction. 

Finally, they point to disputed testimony as evidence that material issues of fact

regarding causation survived.

A. Dr. Newey

The Ecks first challenge the district court’s decision to limit its inquiry to

whether Dr. Rodgers would have prescribed Dilantin to Mr. Eck even if a warning

had been provided. The Ecks argue that the prescribing practices of Dr. Newey,

Mr. Eck’s treating physician, are also relevant, because the interaction of the

Isocet, prescribed by Dr. Newey, and the Dilantin, initially prescribed and later

monitored by him, were the cause of Mr. Eck’s injuries. Thus, the defendants
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must also establish that his practices would not have been altered with the

inclusion of a warning. 

The Ecks emphasize that Dr. Newey testified that had he known of the

interaction between the two drugs, he would have passed this information on to

his patients. We acknowledge that Dr. Newey was the prescribing physician for

Isocet in January 1995, and also prescribed the loading dose of Dilantin to Mr.

Eck in February 1997, and continued to monitor his patient after Dr. Rodgers

resumed the prescribing physician role. However, it is undisputed that Mr. Eck

did not ingest the Isocet concomitantly with Dilantin until April 1997, when his

prescribing physician was Dr. Rodgers. There was no concomitant use of the

drugs when Isocet was originally prescribed, and there is no indication that in

1995 Mr. Eck was suffering from seizures that might require a Dilantin

prescription. That Dr. Newey might have heeded a warning to Mr. Eck about

possible adverse effects were he to prescribe Isocet to him in 1997 is of no

significance given the facts before us. We hold the district court did not err when

it focused exclusively on the testimony of Dr. Rodgers as the prescribing

physician.

B. Did Dr. Rodgers’ Testimony Rebut the Presumption?
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The Ecks next challenge whether the defendants presented evidence to

rebut the presumption that had Dr. Rodgers been properly warned, she would have

read and heeded the warning. The Ecks also question whether Dr. Rodgers’

knowledge about the adverse risks was substantially the same as the risks

presented in the proposed warning. If not, they posit, she would be unable to

incorporate the adverse risks into her risk/benefit analysis.

In rebutting the presumption, the defendants offer Dr. Rodgers’ deposition

testimony. Dr. Rodgers testified that she discussed with Mr. Eck the list of

medications he was taking, but does not recall that Isocet was on the list. She

stated that the Ecks assured her Mr. Eck was not taking any medications other

than those on the list. See Aplt’s App. vol. II, at 573 (depo. of Dr. Rodgers). 

Dr. Rodgers also indicated that she had discussed Mr. Eck’s acetaminophen

intake with him. She told him that his intake of up to twelve tablets a day of

Tylenol was “way too much,” id. at 574, and indicated that she feared this intake

because “[acetaminophen] was hepatotoxic.” Id. She testified that Mr. Eck

indicated that he understood what “hepatotoxic” meant. Id. 

Dr. Rodgers also testified that she was aware of medical literature that

suggested Dilantin might be a “enzyme inducer” that could increase the

hepatotoxicity of acetaminophen. She also testified that she was aware of the
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possibility of an adverse reaction when Dilantin and acetaminophen were taken

together. See id. at 574, 740. 

Dr. Rodgers further testified that she performs a “risk/benefit analysis for

every medication.” Id. at 740. In weighing the risks and benefits, she concluded

that she would have prescribed Dilantin “even if [Mr. Eck] had been on a drug

that had a more frequent hepatotoxicity [than acetaminophen] . . . because the risk

of him having a problem due to his seizure was much greater than him taking the

Dilantin.” Id. at 736. 

The Ecks argue that the evidence offered by defendants failed to rebut the

presumption that Dr. Rodgers would have read and heeded an adequate warning.

The Ecks dispute that Dr. Rodgers or any physician discussed with them Mr.

Eck’s acetaminophen use prior to his liver failure, and point out that Dr. Rodgers’

notes do not reflect such a discussion. See id. at 278, 731, 800. However, Mrs.

Eck does recall faxing a list of her husband’s prescriptions to Dr. Rodgers, and

that they discussed the medications he was taking. The Ecks also point to Dr.

Rodgers’ testimony that she generally does not “particularly find Tylenol to be

effective” and that it “has a number of things that make it less than an attractive

drug to use,” including its “potential for hepatotoxicity” as evidence that she

would have changed her course of treatment. Id. at 577. 
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The Ecks construe Dr. Rodgers’ “heeding” an adequate warning to mean

she would have given the warning. However, “‘heed’ in this context means only

that the learned intermediary would have incorporated the ‘additional’ risk into

[her] decisional calculus.” Thomas , 949 F.2d at 814. In the risk/benefit analysis

of drug prescription, the prescribing physician “can choose to use the product and

face its risks, or choose not to use the product and lose its potential benefits. 

Generally, using the product will present the less risky of these two alternatives.” 

Id. at 813; see also Talley v. Danek Med., Inc. , 179 F.3d 154, 163 (4th Cir. 1999)

(applying Virginia law) (noting that “the prescribing physician can take into

account the propensities of the drug, as well as the susceptibilities of [her]

patient” and has “the task of weighing the benefits of any medication against its

potential dangers”).

We also disagree with the Ecks’ construction of the burden shifting under

the learned intermediary doctrine. Dr. Rodgers testified that even if she knew Mr.

Eck was taking a drug with a more frequent hepatotoxicity enzyme, she would

have still prescribed Dilantin to Mr. Eck . We hold the defendants provided

sufficient evidence that Dr. Rodgers would have not changed her course of

treatment. See Woulfe , 965 F. Supp. at 1485; Garside , 976 F.2d at 80 (“Where

the manufacturer fails to provide the physician with an adequate warning, courts

have held that the manufacturer may still be shielded from liability if it can show
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that the prescribing physician would not have heeded an adequate warning.”); see

also Plummer v. Lederle Labs. , 819 F.2d 349, 358-59 (2d Cir. 1987) (applying

California law) (granting judgment as a matter of law and noting that “the

plaintiff failed to prove that a proper warning would have altered the doctor’s

conduct”).

C. Did Dr. Rodgers have Substantially the Same Knowledge of

Adverse Risks that the Warning Would have Imparted?

 The Ecks next propose that because Dr. Rodgers’ testimony did not imply

that she had substantially the same knowledge of the adverse risks as the proposed

warning would have reflected, her testimony did not demonstrate “unequivocally

that s/he knew at the relevant time all the information which would have been

included in a warning.” Garside , 976 F.2d at 82. Dr. Rodgers testified that she

was aware of a “scientific hypothesis” that the hepatotoxicity of acetaminophen is

increased when used in conjunction with Dilantin, but she did not appear certain

of the interaction between a therapeutic dose of acetaminophen and Dilantin. 

Aplt’s App. vol. II, at 574, 740. Thus, she was unable to incorporate this

knowledge into her risk/benefit analysis of Mr. Eck’s course of treatment.

The Ecks cite Christopher v. Cutter Labs. , 53 F.3d 1184, 1192 (11th Cir.

1995) (applying Florida law) in support of their contention that Dr. Rodgers must

have unequivocal knowledge of the effects of the interaction of the drugs. In
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Christopher , the Eleventh Circuit examined whether the plaintiffs had presented

substantial evidence that absence of an adequate warning was a proximate cause

of the injury. The defendant manufacturer challenged a jury instruction that

required the jury to find that, at the time in question, the prescribing physician

had a knowledge of “reasonable evidence” of the connection between AIDS and

blood products. Id. at 1193. The given warning required only a knowledge that

the “possibility exists” that AIDS could be transmitted through blood products. 

Id. There was no testimony that physicians in general or that the prescribing

physician understood that there was reasonable evidence of an association

between AIDS and blood products during the relevant timeframe. The Eleventh

Circuit held that the district court erred when it required the manufacturer to

establish “reasonable evidence” of the risk, which imposed “a higher and

erroneous layer of proof on its affirmative defense” and that the error required a

new trial. Id. at 1193.

In the present case, we are faced with a very different set of facts: Dr.

Rodgers has testified that she is aware that Dilantin is an enzyme inducer, one

that could increase the hepatotoxicity of acetaminophen. She also testified that

she was aware of the possibility of an adverse reaction when Dilantin and

acetaminophen were taken together. Most importantly, she testified that even if

she knew Mr. Eck was taking, or might take, a drug with a more frequent
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hepatoxicity enzyme than acetaminophen, she still would have prescribed

Dilantin, “because the risk of him having a problem due to his seizure was much

greater than him taking the Dilantin.” Aplt’s App. vol. II, at 736. See also

Thomas , 949 F.2d at 811-15 (holding that a warning stating that seizures had

occurred in 9 of 400,000 patients who had ingested the drug Accutane would not

have altered physician’s behavior where he testified that he was aware at the time

he prescribed the drug of “the possibility that Accutane may have caused seizures

in very rare cases”); Plummer , 819 F.2d at 358 (holding that where physician

testified he “was aware of the risks of contact polio,” a warning stating that an

unimmunized person should avoid contact with a polio vaccinee for 30 days

would not have altered his behavior); Stanback v. Parke, Davis & Co. , 657 F.2d

642, 645 (4th Cir. 1981) (applying Virginia law) (holding that a warning stating

that there was a risk of acquiring a neurological disorder from ingesting the drug

Fluogen would not have altered physician’s behavior where his “decisions and

actions [were] made in full knowledge of [that] information”); Windham v.

Wyeth Labs., Inc. , 786 F. Supp. 607, 612 (S.D. Miss.1992) (applying Mississippi

law) (holding that a warning stating that a pregnant patient who uses Phenergan

suppositories might suffer adverse consequences would not have altered

physician’s behavior where he testified that he was aware of such risk and

“weighed the risk of the drug against the benefit of the drug” before prescribing
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it). Cf. Garside , 976 F.2d at 82 (holding where physician’s affidavit stated he

was aware of “alleged connection” between the combined ingestion of

phenobarbital and amoxicillin and the risk of toxic epidermal necrolysis did not

suggest the physician knew of the causal connection). 

Mr. Eck’s reliance on Tatum v. Schering Corp. , 795 F.2d 925, 927 (11th

Cir. 1996) (applying Alabama law), is similarly misplaced. There, as in Garside ,

the prescribing physician was not adequately warned of the degree or extent of

serious adverse effects. The Tatum court held that a jury might have concluded

the physician, armed with this knowledge, might have reconsidered her decision

to prescribe the drug. See id. Here, Dr. Rodgers testified that she still would

have prescribed Dilantin, because the risk of seizure was more severe than the

risk of hepatotoxicity induction. Thus, Dr. Rodgers was already aware of the

medical risk that the warning would have imparted, and having integrated this

knowledge into her risk/benefit calculation, determined her decision to prescribe

would remain unchanged. See e.g. , Garside , 976 F.2d at 80 (collecting cases and

stating “[w]here the manufacturer fails to provide the physician with an adequate

warning, courts have held that the manufacturer may still be shielded from

liability if it can show that the prescribing physician would not have heeded an

adequate warning . . . [and] have reasoned that the physician’s conduct acts as an

intervening-superseding cause of the plaintiff’s injury which vitiates any liability
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on the part of the manufacturer”); Stanback , 657 F.2d at 645-46 (stating that “the

manufacturer cannot be said to have caused the injury if the doctor already knew

of the medical risk”); Wooten v. Johnson & Johnson Prods, Inc. , 635 F. Supp.

799, 803 (N.D. Ill.1986) (noting that “[c]ourts have held consistently that a drug

manufacturer is entitled to summary judgment where the prescribing physician is

aware of the risks associated with a drug”) (citing Goodson v. Searle Labs. , 471

F. Supp. 546 (N.D. Conn. 1978), and Cobb v. Syntax Labs. , 444 So. 2d 203 (La.

App. 1983)). 

Oklahoma courts have not considered whether a physician’s conduct

automatically acts as an intervening cause relieving the manufacturer of liability,

but instead shifts the burden back to the plaintiff to allow him to controvert the

physician’s testimony. See Woulfe , 965 F. Supp. at 1485-86. If the Ecks can

“produce sufficient evidence to create a triable issue of the question of

causation,” Garside , 976 F.2d at 81, they will defeat a motion for summary

judgment. See Woulfe , 965 F. Supp. at 1485-86 (noting plaintiff was unable to

establish that failure to warn was a proximate cause of injuries and granting

summary judgment to defendant). 

D. Material Fact Questions Regarding Causation
-24-

Finally, the Ecks contend that even if the defendants successfully rebutted

the presumption that a proper warning would have been heeded, they satisfied

their burden by presenting sufficient evidence to create a material fact as to

causation by casting doubt upon the credibility of Dr. Rodgers. Ordinarily, what

constitutes the proximate cause of any injury is a question of fact. See Lefthand

v. City of Okmulgee , 968 P.2d 1224, 1226 (Okla. 1998). “However, the question

of proximate cause becomes a question of law when the facts are undisputed and

there is no evidence from which a jury could reasonably find a causal connection

between the allegedly negligent act and the injury.” Id.

The Ecks challenge Dr. Rodgers’ credibility, and note that she formerly

conducted research for several pharmaceutical companies. As the district court

observed:

These facts standing alone, however, merely offer speculation as to Dr.

Rodgers’ motives for testifying and they are clearly insufficient to call

into question either Dr. Rodgers’ credibility or the veracity of her

statements.

Aplt’s App. vol. III, doc. 31, at 8 (Dist. Ct. Order filed Jan. 18, 2000). The

speculative nature of this argument is increased by the fact that if anything, Dr.

Rodgers’ testimony would have enhanced her own exposure to liability. Absent

evidence suggesting Dr. Rodgers was otherwise influenced by the defendants, we,

like the district court, find no reason to question her credibility or the truth of her

testimony.
-25-

 Even viewing the facts most favorably to the Ecks, we cannot disagree

with the district court’s conclusion that Dr. Rodgers would have prescribed

Dilantin no matter how carefully the Ecks proposed or refined the phrasing of the

suggested warning. Dr. Rodgers testified about her independent knowledge of the

risk of the potential interaction between the two drugs, and indicated that if

presented with even a higher risk, she would have prescribed Dilantin. The Ecks

have failed to controvert this testimony and have failed to create an issue of fact

of whether defendants’ failure to warn was the proximate cause of their injuries.

IV. CONCLUSION

We agree with the district court that the Ecks are unable to demonstrate that

a warning would have changed Dr. Rodgers’ or Dr. Newey’s behavior at the time

of prescribing Dilantin and Isocet, respectively. The Ecks are, in turn, unable to

establish that the alleged failure to warn of the possible adverse reactions between

the drugs was the proximate cause of Mr. Eck’s injuries. Accordingly, we

AFFIRM the district court’s grant of summary judgment to defendants.