Although nifedipine is commonly administered sublingually in the clinical setting, a comparison of the serum concentrations obtained by this route vs oral administration has not been previously made. Nifedipine serum concentrations were measured in 6 healthy subjects following sublingual or oral administration of one nifedipine 10 mg capsule. Serum nifedipine concentrations were measured at regular intervals and demonstrated that sublingual administration produced measurable nifedipine concentrations sooner than oral administration. Peak nifedipine serum concentrations were less following sublingual administration (41.9 +/- 24.9 ng/ml) than following oral administration (99.6 +/- 49.8 ng/ml, p less than 0.05). The time to peak nifedipine serum concentration was also longer following sublingual administration than with the oral dose (74 +/- 24 minutes vs 40 +/- 14 minutes, p less than 0.05). Despite these differences, the areas under the serum concentration-time curve of the two routes of administration were similar. These differences in nifedipine concentrations may be an important consideration when choosing the route of administration of nifedipine.