Q. I keep reading about using herbals in place of prescription drugs, but I worry about the risks. What do you think about using hawthorn to help lower high blood pressure?

A. I know that there's a lot of hype about herbal remedies out there, but I always side with the medication that has the most information available about the outcomes and problems associated with using it.

Sign up for the AARP Health Newsletter.

Hawthorn, as you may know, is a common shrub in the rose family that grows throughout the world. A wide variety of preparations can be made from its leaves, flowers and berries, including capsules and liquid extracts (nonstandardized and standardized), tinctures and even tea. The U.S. Food and Drug Administration does not require any of them to be screened for effectiveness or safety.

With prescription drugs, on the other hand, we can have an expectation of strict quality-assurance standards and, more often than not, a body of research that will tell us what to expect when we take them — both good and bad.

While I do recommend herbal and nutraceutical products for some purposes, when it comes to dealing with blood pressure I do not. That's because I don't want to guess or assume anything about a product that's often what lies between a stroke or death and having a long, productive life.

I agree with experts at the University of Maryland Medical Center, who have concluded that "not enough research has been done to say whether hawthorn is effective at lowering blood pressure — and if so, by how much."

It's also important to remember that hawthorn should not be used with digoxin, which is used to treat congestive heart failure and heart rhythm problems. The same goes for beta-blockers or calcium channel blockers, two classes of blood-pressure medications, as hawthorn can amplify their effects to dangerous levels. Hawthorn can also interact with other medications.

If you have high blood pressure, you should talk with your physician or other health care professional before taking hawthorn.

Ask the Pharmacist is written by Armon B. Neel Jr., PharmD, CGP, in collaboration with journalist Bill Hogan. They are coauthors of Are Your Prescriptions Killing You?, which was published in July by Atria Books.

You may also like:

• Why you should tell your doctor if you take supplements.
• 10 superfoods you need to know to eat healthy.

Go to the AARP home page  for tips on keeping healthy and sharp, and great deals.