SACKETT, C.J.

Sue Ellen Bellville, riding as a passenger on her husband Roger's motorcycle, was fatally injured when the cycle collided with an automobile driven by Gary Schuller. Plaintiffs-appellees Roger Bellville, administrator of the estate of Sue Ellen Bellville, and the estate of Sue Ellen Bellville sued defendant-appellant Farm Bureau Mutual Insurance Company (Farm Bureau), seeking recovery under a policy issued to Roger insuring the motorcycle. In the suit plaintiffs contended, among other things, that Schuller's $50,000 automobile liability policy was insufficient to cover damages proximately caused by Schuller's negligent operation of his motor vehicle. Plaintiffs contend defendant should pay the limits of insurance available under the underinsured motorist provision of the policy issued to Roger insuring the motorcycle as further compensation for the injuries caused by Schuller's negligence. The matter was tried to a jury, which was instructed to determine the respective fault, if any, of Roger and Schuller, and the damages to Roger and Sue Ellen's estate as a result of the accident. The jury found Roger to be five percent at fault and Schuller to be ninety-five percent at fault. Damages were computed to be $756,714.95, and judgment was entered against Farm Bureau for $300,000, the limits of its underinsured liability coverage. On appeal Farm Bureau claims the trial court erred in (1) excluding evidence of Roger Bellville's drug use before and after the accident, (2) limiting the testimony of its expert, and (3) improperly instructing the jury regarding Roger Bellville's negligence. We affirm.

I. BACKGROUND FACTS AND PROCEEDINGS.

The accident happened on October 9, 1999, when the Bellville motorcycle, traveling north, and a vehicle driven by Guy Schuller, traveling south on Edgewood Road in Cedar Rapids, Iowa, collided at the intersection of Edgewood and O Avenue. Schuller, hoping to turn left on O Avenue, entered the intersection on a green light, and as the light turned yellow, began his turn. The Bellvilles, who were still headed north on Edgewood Road, continued through the intersection. Roger Bellville indicated Sue Ellen stated upon seeing the light turn yellow, "We're not going to make it," but he did not believe he could safely come to a stop before the intersection and continued through the intersection, hitting the rear passenger side of Schuller's automobile as it was turning left.

Roger estimated he was traveling thirty to thirty-five miles per hour prior to the accident. Officers involved in the accident reconstruction estimated Roger Bellville's motorcycle was traveling 21.65 miles per hour when he hit Schuller's automobile. Roger testified in a deposition that he saw the light change to yellow at least thirty feet prior to the stop bar. At trial Roger testified he began braking when he saw the yellow light, but believing he could not come to a full stop before the intersection, continued slowly through the intersection, ultimately locking his brakes upon seeing Schuller's car.

Following the accident, Roger submitted to a preliminary breath test, which indicated a level of .000. Officers then offered Roger a urine test for drugs other than alcohol, which he submitted to. No officer who interviewed Roger following the accident indicated there was any sign he appeared to be under the influence of any drug. Roger's urine tested positive for marijuana at a level in excess of 135 nanograms per milliliter. According to expert testimony, this level is consistent with marijuana use up to three days prior to the test.

Prior to trial Farm Bureau sought to obtain Sue Ellen's medical records as part of its discovery. Roger signed an authorization for release of Sue Ellen's records. Despite the fact that Roger did not authorize release of his medical records to Farm Bureau, his health care providers turned over his medical records as well. In those records were references to Roger's past inpatient treatment for cocaine abuse in approximately 1981, and his past use of marijuana.

Roger admitted in an August 4, 2001 deposition that he had been charged with possession of marijuana in November of 2000 following a traffic stop. In that deposition he denied ever using marijuana on a regular basis, instead indicating he used it only on "rare occasions."

At trial Farm Bureau sought to introduce evidence of Roger's marijuana use in the years both before and after the accident. It also sought to introduce testimony by its expert as to the effects of long-term marijuana use on the brain. In a deposition Farm Bureau's expert, Dr. Weis, testified to the long-term effects of marijuana and other drug use and what the effects of these drugs would have been on Roger's ability to respond to the changing traffic signal. In arriving at his opinions, Dr. Weis relied on Roger's medical records.

The trial court excluded testimony regarding long-term effects of drug use by Dr. Weis as more prejudicial than probative and limited Dr. Weis's testimony and Farm Bureau's questioning to the circumstances immediately surrounding the accident, including the results of the urine test administered following the accident. The trial court disallowed any other references to Roger's drug use.

We first address Farm Bureau's argument that the trial court abused its discretion in disallowing evidence of Roger's history of drug use and expert testimony regarding the effects of this evidence. Farm Bureau also argues it should have been able to use the medical records to impeach Roger Bellville's statements.

II. SCOPE OF REVIEW

We review evidentiary decisions of the trial court for abuse of discretion. Shawhan v. Polk County, 420 N.W.2d 808, 809 (Iowa 1988). In order to show an abuse of discretion, one generally must show that the court exercised its discretion on grounds or for reasons clearly untenable or to an extent clearly unreasonable. Crookham v. Riley, 584 N.W.2d 258, 267 (Iowa 1998).

III. ADMISSIBILITY OF EVIDENCE OF "CHRONIC" DRUG USE

In refusing to allow the introduction of evidence from Roger's medical records and Dr. Weis's testimony about them, the trial court reasoned this evidence would be more prejudicial than probative under Iowa Rule of Evidence 5.403. The court further expressed concern that Roger had not consented to the release of the records and that they were therefore still subject to the physician-patient privilege.

Roger's medical records are not admissible unless he waives his physician-patient privilege, which he did not do. See Chung v. Legacy Corp., 548 N.W.2d 147, 149-51 (Iowa 1996). The trial court was correct to deny admission of those records and to disallow testimony by Dr. Weis relying on them.

With respect to the other evidence indicating marijuana use, specifically (1) Roger's deposition testimony admitting rare use of it in his past, and (2) his November 2000 arrest for marijuana possession, the questions we are still faced with is whether the evidence of drug use in the years preceding and succeeding the accident are probative of chronic drug use on Roger's part such that his judgment would have been impaired at the time of the accident, and whether this evidence, if probative, is more probative than prejudicial.

The following is the evidence which Farm Bureau argues establishes "chronic drug use": (1) the inadmissible 1993 medical report; (2) the inadmissible 1995 medical report; 3) the urine tests administered immediately following the motorcycle accident, indicating Roger had likely smoked marijuana within the past three days; (4) evidence not admitted of Roger's deferred sentence for possession of marijuana in November of 2000; and (5) evidence not admitted of Roger's admitted use of marijuana on rare occasions in the past in his August 4, 2001 deposition.

Of the above evidence, the urine test evidence would be the most probative of Roger's state of mind at the time of the accident. At trial, however, a toxicologist admitted that urine test levels do not measure mental impairment. Farm Bureau therefore sought to demonstrate mental impairment through the above evidence of "chronic drug use."

An admission in August 2001 to rare marijuana use in the past, together with an admission to a November 2000 arrest for marijuana possession, is not probative of ongoing and chronic drug use sufficient to be relevant to Roger's state of mind in the 1999 accident.

Farm Bureau contends Ward v. Loomis Bros., 532 N.W.2d 807, 811 (Iowa Ct.App. 1995), and Duncan v. City of Cedar Rapids, 560 N.W.2d 320, 324-25 (Iowa 1997), support the proposition that past drug use is admissible to show mental impairment. These cases are distinguishable. Ordinarily, evidence of prior drug use is not admissible to prove intoxication at the time of an accident. Iowa R. Evid. 5.404( b), cited in Duncan, 560 N.W.2d at 325. In Loomis, 532 N.W.2d at 810, there was a direct link between the decedent's use of marijuana at work and the accident which was the subject of the suit, as the accident occurred at work. In Duncan, 560 N.W.2d at 325, the plaintiff contested blood test results showing the victim's intoxication, thereby opening the door to evidence showing an absence of mistake in those blood tests. See Iowa R. Evid. 5.404( b). Here there is no direct link between the dates of Roger's historical marijuana use and the accident, and there is no separate evidentiary rule allowing admission of the drug use. Instead, Farm Bureau is attempting to introduce the evidence for precisely its prohibited purpose: to show Roger was a chronic user of drugs in conformity with his actions on these previously demonstrated dates, and thus implying a brain impairment due to this chronic use. We reject Farm Bureau's argument. The trial court did not abuse its discretion in limiting evidence of Roger's drug use.

Farm Bureau argues in the alternative that the drug evidence was relevant for purposes of determining Roger's damages according to life expectancy. Even if the evidence is relevant for purposes of determining life expectancy, we conclude the prejudice of that evidence, which we have already established, outweighs the probative value. See Shawhan v. Polk County, 420 N.W.2d 808, 809-10 (Iowa 1988).

Farm Bureau next contends it should have been allowed to use the medical records to impeach Roger's testimony, as Roger contradicted his medical records in trial testimony and on deposition. Chung v. Legacy Corp., 548 N.W.2d 147, 151 (Iowa 1996) held otherwise. There, Chung sued one Karns for damages he contended were caused by Karns's negligence in operating a vehicle while under the influence of alcohol. Chung, 548 N.W.2d at 148. Karns denied the allegation of intoxication. Id. Chung sought the court's permission to take the deposition of the physician who treated Karns immediately following the accident and sought the production of Karns's medical records to show Karns's state of intoxication. Id. Karns resisted, contending that the physician-patient privilege protected this evidence from disclosure to third parties. Id. In Chung the court recognized the rules of privilege were not designed to facilitate the fact-finding process. See id. Rather, the rules of privilege exist to protect certain communications from disclosure even though the confidences may otherwise be admissible. See id. While such a rule may preclude the discovery and admission of relevant evidence, that is no reason not to apply the privilege. See id. at 151. "The waiver does not depend solely on the relevance of the privileged material, or on the adversary's need, no matter how strong, for the communication." Id. (quoting Muller v. Rogers, 534 N.W.2d 724, 727 (Minn.Ct.App. 1995)). The Iowa legislature presumably balanced the competing interests when it made the policy decision to adopt the physician-patient privilege. Chung, 548 N.W.2d at 151. The trial court did not abuse its discretion in concluding the evidence was inadmissible.

IV. ADMISSIBILITY OF EVIDENCE OF "CHRONIC" DRUG USE THROUGH EXPERT TESTIMONY

We next address Farm Bureau's argument that Dr. Weis's opinion of Roger's chronic drug use should have been admissible. We have concluded Roger's medical records were not admissible because he did not release them and that the district court did not abuse its discretion in refusing to admit the other drug use evidence. Therefore Dr. Weis's expert testimony based on that evidence is also inadmissible, and the trial court did not abuse its discretion in refusing to admit it.

V. JURY INSTRUCTIONS

Farm Bureau also argues that the trial court erred in giving Jury Instruction 22 because it overemphasized the plaintiff's theory of the case. Our standard of review concerning alleged error with respect to jury instructions is for correction of errors at law. Herbst v. State, 616 N.W.2d 582, 585 (Iowa 2000). "Parties to lawsuits are entitled to have their legal theories submitted to a jury if they are supported by the pleadings and substantial evidence in the record." Sonnek v. Warren, 522 N.W.2d 45, 47 (Iowa 1994). The jury instructions must thoroughly and fairly convey the law applicable to the issues presented. Id. When weighing the sufficiency of the evidence to support a requested instruction, we view the evidence in a light most favorable to the party seeking the instruction. Id.

Jury Instruction 22 stated the following:

There has been test evidence that Roger Bellville had marijuana metabolites in his urine after the collision. The concentration was in violation of the law. In considering the import of such evidence, you should consider all other evidence in the case, or lack thereof, in determining whether marijuana use was a proximate cause of any acts or omissions causing the collision. Marijuana use on any prior occasion other than close enough in time to the collision to be such proximate cause may not influence your deliberation on any issues in this case.

We conclude Jury Instruction 22 was a correct and thorough statement of the law and did not unduly emphasize the plaintiffs' case. An act of driving while intoxicated is not negligence per se and thus not conclusive evidence of contributory evidence so as to bar recovery. Sechler v. State, 340 N.W.2d 759, 767 (Iowa 1983). In order to conclude an intoxicated driver is contributorily negligent, the evidence must show the driver's intoxicated condition translated into outward conduct which was negligent and bore a causal relation to the injury. Id. The matter of intoxication and its causal relationship to the injury are questions that must be decided by the fact finder. Id. We affirm on this issue.

AFFIRMED.