PER CURIAM.

Plaintiffs brought an action against defendants for injuries and damages sustained as a result of Helen Formella's taking the drug Tandearil. The complaint alleged malpractice on the part of Dr. Murguz in prescribing the drug. It was further alleged that Ciba-Geigy, the manufacturer and distributor of Tandearil, was jointly and severally liable for plaintiff's injuries by failing to adequately warn Dr. Murguz of the dangers of the drug and by promoting its use.

After the first day of trial, plaintiffs entered into a settlement agreement with Dr. Murguz. He was dismissed from the action and no appeal has been taken therefrom.

Ciba-Geigy moved for a directed verdict of no cause of action at the close of plaintiffs' proofs. The motion was granted by the trial court and plaintiffs appeal.

At trial, Dr. Murguz stated that Helen Formella, an elderly woman, came to him on May 5, 1973, complaining of low back pain. He diagnosed osteoarthritis and prescribed Tandearil. She returned to Dr. Murguz's office in two weeks, at which time he continued the drug treatment. No blood tests were conducted at this time or at any time during her treatment.

On June 19, 1973, Mrs. Formella called Dr. Murguz to complain of multiple bruises and tiredness. He stated that he immediately suspected that Tandearil had caused her to develop a blood dyscrasia. He ordered her to stop taking the drug and to report to a hospital for tests. His suspicions were confirmed. Mrs. Formella was extremely ill for several weeks from the aplastic anemia which had occurred as the direct result of taking Tandearil.

Plaintiffs first assign as error the trial court's ruling that evidence of Ciba-Geigy's 1965 to 1973 marketing plans for Tandearil was inadmissible. The court ruled that evidence of those plans was irrelevant. Plaintiffs allege that evidence of those plans was relevant in that such evidence displayed the strategy of Ciba-Geigy in overpromoting the drug. Plaintiffs argue, in particular, that the information given to Dr. Murguz between 1965 and 1969 by "detail men", salespersons who call on doctors in order to promote the use of that company's drugs, is relevant in determining whether the drug company was negligent in failing to adequately warn him of the hazards of the drug.

Although we find plaintiffs' arguments plausible in theory, we hold that the trial court did not err in excluding the evidence in this case. Dr. Murguz testified that he read the Physician's Desk Reference manual (PDR) in part the first time that he prescribed Tandearil in 1965. After the first prescription, he no longer looked at the PDR or the quarterly supplements prior to prescribing the drug. Instead, he relied upon the statements of Ciba-Geigy detail men, who told him that Tandearil was a good drug "with a safety margin". He stated that if a drug is on the market and being "detailed", it must be safe.

It is obvious from Dr. Murguz's testimony that he knew Tandearil, like all prescription drugs, has some dangers that must be guarded against by the physician. He knew that taking Tandearil for a lengthy period of time could cause blood dyscrasia, yet he never conducted a blood test on Mrs. Formella or read the PDR. Indeed, he knew from the moment Mrs. Formella phoned him, describing the symptoms, that she had contracted the disease from taking Tandearil.

We conclude from his testimony that the negligence of Dr. Murguz is the intervening, independent and sole proximate cause of Mrs. Formella's injuries. Even if Ciba-Geigy had been negligent in overpromoting the use of the drug through its detail men, that negligence was not the proximate cause of Mrs. Formella's injury. Love v Wolf, 226 Cal.App.2d 378; 38 Cal.Rptr. 183, 196 (1964). Dr. Murguz simply chose to ignore what he knew: that the use of Tendearil over several weeks could cause blood dyscrasia.

In addition, our review of the record reveals that there is no evidence that the drug was overpromoted. Dr. Murguz stated he was told by detail men that the drug was good "with a safety margin". Although some of the early literature tends to play down the possible side effects of the drug and recommends its use for extended periods of time, all of the literature submitted to this Court includes a warning that blood tests should be frequently conducted on the patient. Therefore, plaintiffs have failed to meet the burden of showing that the evidence is relevant.

Finally, plaintiffs argue that the trial court erred in granting the motion for a directed verdict. They assert that the testimony of their expert witness, Dr. Lerman, was sufficient to allow the question of negligence to go to the jury. Dr. Lerman stated that he felt the PDR warning and package inserts were lengthy and inconsistent, thereby rendering them inadequate. He cited the example of the warning that the drug should not be given to persons who are senile as being contradictory with the later warning that the drug should not be used for over a week in persons over age 60. Dr. Lerman also testified that he did not prescribe the drug to people over age 60 because the PDR and package insert information warn against such use. He concluded that the warnings were adequate, if read.

The standard of review of directed verdicts is outlined in Cody v Marcel Electric Co, 71 Mich. App. 714, 717; 248 N.W.2d 663 (1976), as follows:

"Directed verdicts, particularly in negligence cases, are viewed with disfavor. When a fact question is presented upon which reasonable persons could reach differing conclusions, the trial judge may not take the question from the jury. In deciding whether the trial court erred in entering a directed verdict, we review all the evidence presented to determine whether a question of fact existed. In so doing, we view the evidence in a light most favorable to the nonmoving party, granting him every reasonable inference and resolving any conflict in the evidence in his favor. If the evidence viewed in this manner establishes a prima facie case, we must reverse the trial court's grant of a directed verdict. Caldwell v Fox, 394 Mich. 401; 231 N.W.2d 46 (1975)."

Plaintiffs' cause of action against Ciba-Geigy is not based upon any defect in the drug but upon the failure of the drug company to adequately warn physicians of the hazards of the drug. When liability turns on the adequacy of a warning, the issue is one of reasonable care. Smith v E R Squibb Sons, Inc, 405 Mich. 79, 90; 273 N.W.2d 476 (1979). The adequacy of the warning is a question of fact, properly left to the jury. Gutowski v M R Plastic Coating, Inc, 60 Mich. App. 499, 506-508; 231 N.W.2d 456 (1975).

In the case at bar, we agree with the trial court's conclusion that there is no evidence that Ciba-Geigy failed to adequately warn physicians, through the package inserts, PDR and other publications, that the drug had possible harmful effects. The materials stated that blood tests should be conducted weekly for persons who were aged. The drug was contraindicated for persons with drug allergies, such as Mrs. Formella's allergy to penicillin. It was recommended that older people not take the drug for more than a week. Dr. Lerman's testimony, the only possible evidence presented that indicated Ciba-Geigy may have been negligent, revealed that the warning was adequate, if read.

Furthermore, the fact Dr. Murguz failed to read the package inserts and PDR negates any possible negligence on the part of Ciba-Geigy in not emphasizing the hazards in those publications. Again, we find that Dr. Murguz's negligence is the intervening, independent and sole proximate cause of Mrs. Formella's illness.

Affirmed, costs to defendant.