Determining the effects of grapefruit juice on pharmacokinetics of oral digoxin (a drug often

prescribed for heart ailments) was the goal of a study by Parker et al. (A-1). Seven healthy

nonsmoking volunteers participated in the study. Subjects took digoxin with water for 2 weeks,

no digoxin for 2 weeks, and digoxin with grapefruit juice for 2 weeks. The average peak plasma

digoxin concentration (Cmax) when subjects took digoxin with water is given in the first column of

the following table. The second column gives the Cmax concentration when subjects took digoxin

with grapefruit juice. May we conclude on the basis of these data that the Cmax concentration is

higher when digoxin is taken with grapefruit juice? Let a :5.