Furosemide-probenecid interaction as a laboratory exercise for undergraduate education in clinical pharmacology

The aim of this study was to determine the easiness, reproducibility, and safety of a laboratory exercise for a drug interaction between furosemide and probenecid.

From 1995 to 1999 approximately 100 medical students participated in the exercise each year after they gave written informed consent. The students were randomly assigned to one of the three groups in a double-blind fashion: group 1, placebo plus 20 mg of furosemide; group 2, 250 mg of probenecid plus 20 mg of furosemide; and group 3, 1000 mg of probenecid plus 20 mg of furosemide. The students took probenecid or its placebo 1 hour before furosemide. Urine volume and urinary sodium excretion were measured for 3 hours after furosemide. At the end of the exercise in 1999, students responded to several questionnaires concerning the utility of furosemide.

The entire course of the exercise was completed within half a day. The following findings were obtained every year. (1) Probenecid dose dependently blunted the diuretic effects of furosemide. (2) Time courses of the diuretic effects were altered by probenecid. Ten to twenty percent of the students had slight complaints but completed the exercise without any medications. Finally, more than 80% of the students considered the exercise to be useful.

The data suggest that the exercise of the drug interaction between furosemide and probenecid is easy to perform, reproducible, and safe. Through the experience of the laboratory exercise, students will develop an attitude to assess and estimate potential drug interactions before they prescribe drugs.