Phenytoin Recovery From Percutaneous Endoscopic Gastrostomy Pezzer Catheters After Long‐Term In Vitro Administration

Four in vitro administration techniques were evaluated to determine which method would produce the least amount of phenytoin lost with long‐term (14 days) dosing of Dilantin Kapseals (100 mg) or Dilantin suspension 125 mg/5 mL (92 mg) through 20 French percutaneous endoscopic gastrostomy Pezzer catheters. The four in vitro techniques were (1) no dilution or irrigation, (2) irrigation with 10 mL of deionized water, (3) dilution with 10 mL of deionized water, and (4) dilution with irrigation. Similar doses and volumes (3.68 mL) of suspension and capsules were delivered to three separate catheters for each method every 8 hours for 14 days. Each catheter was encased in a 200‐mm glass water jacket and maintained at 37°C for the entire 14 days. Samples were collected 1 hour after administration on days 1, 3, 7, 10, and 14 and analyzed by high‐performance liquid chromatography. The total mean percent change in initial phenytoin for each method was as follows (S = suspension, K = Kapseals, subscript number = method number): S 1 , ‐4.23 ± 20.20 (mean ± SD); S 2 , ‐7.63 ± 14.04; S 3 , ‐0.14 ± 2.31; S 4 , 3.33 ± 5.59; K 1 , ‐9.72 ± 4.60, K 2 , 1.43 ± 3.90; K 3 , ‐3.18 ± 5.59; and K4, 1.39 ± 4.57. These results show that (1) short‐term dosing does not reflect long‐term dosing; (2) the more inefficient the method is, the greater the variability and fluctuation between days; (3) there was no significant difference between Kapseals and suspension if the appropriate method for administration was used; (4) dilution is superior to irrigation for long‐term dosing of suspension; (5) irrigation is superior to dilution for long‐term dosing of Kapseals; and (6) additional dilution and/or irrigation to each dosage form adds little and only increases preparation time. (Journal of Parenteral and Enteral Nutrition 17: 370–374, 1993)