TUESDAY, Dec. 30 (HealthDayNews) -- Doctors tend to prescribe pricey new blood pressure drugs even though research has shown inexpensive treatments are just as effective, says a new study from the University of Michigan.

Diuretics and beta blockers are recommended by the Joint National Commission on High Blood Pressure Treatment as the best treatment for regular high blood pressure.

But a survey of 1,700 primary-care doctors found the doctors preferred such newer drugs as calcium channel blockers and ACE inhibitors, reports Dr. Peter A. Ubel of the University of Michigan Medical School.

In the study, the doctors were given a test case involving a patient with high blood pressure and asked about the effectiveness of the drugs available to treat it.

Despite numerous clinical trials that have shown diuretics and beta blockers to be equally effective in treating uncomplicated high blood pressure, the doctors rated diuretics significantly less effective than the other three drugs and felt beta blockers were more likely to cause side effects.

Ubel also found doctors who favored prescribing the more expensive drugs were more likely to give patients free samples from pharmacuetical representatives. The study appears in the December issue of the Journal of General Internal Medicine.

"The industry influence is pervasive," Ubel says. "I think a lot of physicians do rely on sales representatives to tell them about the latest medications out there."

"It may seem like the doctor's helping patients get more affordable medicine, but it's not a lifetime supply," he adds. "After the free samples run out, the patient is left to pay for a more expensive drug."

More information

Here's where you can learn more about high blood pressure medication.