Many medications administered to frail geriatric patients are not in a liquid form, but are crushed and dissolved in water before their administration through a nasogastric tube (NGT). Some medications are enteric coated and others are extended release. Only sparse information is available on their pharmacokinetics when administered through NGT. The aim of our study was to evaluate the pharmacokinetics of phenytoin administered through an NGT and to compare these with the pharmacokinetics of a group of patients receiving the drug orally. Twenty patients were studied in a stable clinical condition, from the long-term care ward of the Geriatric Medical Center Shmuel Harofeh. They were consistently treated with phenytoin for the prevention of seizure disorders. Patients in group 1 (n = 12) had oropharyngeal dysphagia and received feeding and medications by NGT. Group 2 (n = 8), included age-matched orally fed patients from the same department, who received phenytoin orally. Blood samples for phenytoin concentration were taken at baseline, time 0, and at 1, 3, 4, 6, and 8 hours postdrug administration; phenytoin was measured using the AxSYM assay. The mean daily dose was not statistically different between the 2 groups: 291 +/- 28 (200-300) mg/d and 300 +/- 53 (200-400) mg/d, in the NGT, and the orally fed group, respectively, in one dose. Pharmacokinetic parameters of phenytoin were not significantly different between the 2 groups; trough concentrations, 1.9 +/- 1.7 (0.5-4.9) versus 2.2 +/- 1.8 (1.0-6.5) microg/mL; Cmax, 6.6 +/- 3.4 (2.5-9.1) versus 7.3 +/- 6.7 (2.7-8.4) microg/mL; tmax, 5.1 +/- 3.1 (3.1-8.2) versus 4.6 +/- 2.7 (2.3-8.4) hours; area under the curve, 52.2 +/- 40.1 (41.1-61.2) versus 62.3 +/- 84.7 (30.2-77.2) microg/h/mL, in the NGT fed versus the oral fed, respectively. Phenytoin pharmacokinetic parameters are not significantly different between patients receiving the drug through NGT as compared with those who received it orally, but the implication of the low concentrations measured should be evaluated carefully.