Ibopamine: A Drug That Has Opposite Effects Depending on the Severity of a Patient's Disease

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The summary below is from the full report titled "Confounding by Contraindication in a Nationwide Cohort Study of Risk for Death in Patients Taking Ibopamine." It is in the 3 April 2001 issue of Annals of Internal Medicine (volume 134, pages 569-572). The authors are H Feenstra, RE Grobbee, BA in't Veld, and BHCh Stricker.

What is the problem and what is known about it so far?

Ibopamine is a drug that was used in Europe to treat heart failure, a condition in which the heart cannot pump blood normally. In 1995, a study showed that ibopamine increased death rates in patients who had moderate to severe heart failure. In September 1995, doctors and pharmacists in the Netherlands were officially notified that ibopamine should be used only in patients with mild heart failure. Moreover, the official recommendations for when to use ibopamine were changed according to whether patients had mild or severe heart failure. Whether the change in recommendations resulted in fewer deaths related to ibopamine was not known.

Why did the researchers do this particular study?

To see if an official change in the specific indications for using the drug ibopamine affected death rates related to that drug.

Who was studied?

Researchers followed 739 patients who were taking ibopamine before September 1995 and 407 patients who were taking it after September 1995. All patients had heart failure.

How was the study done?

The researchers identified patients who had received ibopamine from community-based drug-dispensing outlets in the Netherlands. They contacted these patients' general practitioners and asked about patients' medical history and heart failure severity. Prescription data were obtained from computer records. Patients were followed from the date of their first ibopamine prescription until death or the end of the study period.

What did the researchers find?

About three fourths of the patients who died before 1995 were using ibopamine up to the time of their death. Only half of the patients who died after 1995 were taking ibopamine at the time of death. The risk for death increased among patients who took ibopamine before 1995 and decreased among those who took ibopamine after 1995. Overall, patients taking ibopamine before 1995 had about a threefold higher risk for death than patients who were taking ibopamine after 1995.

What were the limitations of the study?

The actual severity of heart failure at the time of death was not clear and was not measured precisely in some patients.

What are the implications of the study?

Certain drugs have different and seemingly opposite effects in patients, even when those drugs are used to treat the same condition or disease. Such confusing differences in effects may be related to several factors, including whether the drug is preferentially avoided in patients with severe underlying disease and whether the drug itself is harmful for particular groups of people but not others.