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Release: Feb. 14, 2000

Antidepressants' benefits should be weighed against interactions with other drugs

IOWA CITY, Iowa – Medications used for mental illnesses are increasing in number and effectiveness, meaning more patients may benefit. A University of Iowa researcher warns, however, that doctors must be aware of these psychotropic drugs' interactions with other drugs, surgical anesthesia and popular over-the-counter herbal medications.

While psychotropic medications help treat mental illnesses that, until a few years ago, had never been treatable with drugs before, keeping track of all the possible side effects and drug interactions from these medications is becoming more difficult. Cindy Marek, Pharm.D., assistant professor (clinical) in oral pathology, radiology and medicine in the UI College of Dentistry, said that predicting the side effects of medications is still possible.

"We do have the ability to predict the intended and unintended results of these drugs," Marek said. "The problem with many new drugs is that they are generally tested on young, healthy people. We don't really see their effects on patients with multiple illnesses, or their interactions with other medications, until the drugs are on the market."

Marek published an article in the November 1999 issue of the Journal of Oral and Maxillofacial Surgery Clinics of North America to inform practitioners as to what antidepressant drugs are available and the possible problems they could pose. The article features a chart enabling antidepressant interaction predictions for physicians.

Psychotropic drugs account for more than 9 percent of prescriptions written in the United States, Marek said. Antidepressants, which are included under psychotropic drugs, are used for mood disorders like depression, which affects nearly 6 percent of the population. The most common antidepressants used in the past, called tricyclic antidepressants, had potential to be toxic to the heart. Newer antidepressants, like selective serotonin reuptake inhibitors (SSRIs) such as Prozac, are safer and currently account for more than 80 percent of new prescriptions written for the treatment of depression. The potential for a variety of interactions still exists, however.

"So many times we look at drug interactions in terms of making a toxic combination," Marek said. "Now we are exploring more of the reverse case. One medication causes another to have less effect and be less available to the body. Sometimes the interaction can even cause a buildup of unused medicine in the body."

Marek, who also is an assistant professor in the UI College of Pharmacy, said an important example of this type of interaction is Prozac. When dental patients have their wisdom teeth removed, they receive codeine for the pain. However, if these patients are also taking Prozac, the antidepressant interferes with an enzyme that activates the codeine. Therefore, the codeine will have little or no effect.

In addition to interacting with other medications, antidepressants can also interact with anesthesia or other drugs used in surgery, causing seizures in some cases, Marek said.

More risk is present with the increasingly popular herbal medications found on grocery shelves and in infomercials, Marek said. Herbal medicines themselves may interact with surgical drugs and other medications.

A potentially dangerous example is St. John's Wort, an herbal remedy often used to treat depression. St. John's Wort can interact with other antidepressants and result in elevated blood pressure in certain situations. Many herbal agents will also interfere with blood clotting and can prolong bleeding during surgery.

The Food and Drug Administration has allowed herbal medications to be marketed as nutritional supplements, meaning they are less regulated than prescription and over-the-counter drugs, Marek noted.

"The public has huge faith that if these medicines are bad, they will be taken off the market," she said. "This isn't necessarily true. In the meantime, 70 percent of patients who are taking these medicines don't voluntarily report this to their doctors. They're probably afraid that doctors will scoff at them, but also they don't perceive herbal remedies as actual drugs. They may not realize that if a doctor prescribes another medication, it has potential to interact with the herbals."

Marek recommends that doctors add some questions when they take patient histories to anticipate any problems with medications.

"Practitioners should ask patients if they are on any prescriptions, if they are taking any over-

the-counter drugs, and finally if they are taking any herbal medicines. By being judicious about the mixes of different medicines and being aware of the potential interactions, problems can be avoided," she said.

Despite the potential for problems with antidepressants, Marek is adamant that the increase of drugs that can aid mental illnesses is a key to improving patients' lives.

"It is only a benefit that we have medications for mental illnesses," she said. "A lot of these problems are caused by a chemical imbalance in the brain. Medications can correct this and return patients to a normal quality of life. For example, up to a few years ago, there was nothing for patients with obsessive-compulsive disorder, which is an extremely debilitating disease. With antidepressants and other medications, we can give people back their lives."