Effect of tubing length on adsorption of diazepam to polyvinyl chloride administration sets

Am J Hosp Pharm. 1986 Nov;43(11):2789-94.


The effect of administration-set tubing length on adsorption of diazepam to polyvinyl chloride (PVC) tubing was studied, and a simple equation for calculating the dose of diazepam delivered to the patient during an i.v. infusion of diazepam was derived. Diazepam solutions were prepared in 500 mL of 0.9% sodium chloride injection in glass bottles to a final theoretical concentration of 50 micrograms/mL. PVC administration sets were attached to the bottles, and the tubing was then cut to various lengths or the entire length was used for infusion of diazepam solution at a constant rate of 60 mL/hr. Samples of the diazepam solution were collected in glass test tubes initially and after infusion periods of 0.25, 0.5, 0.75, 1.00, 1.50, 2.00, 3.00, and 4.00 hours. Diazepam concentrations were assayed spectrophotometrically in duplicate, and each infusion trial was performed three times. The mean diazepam concentrations in the bottles remained within 100 +/- 1% of initial concentration throughout the study. However, solution samples collected after the four-hour infusion period varied in concentration from 45.5 micrograms/mL using the 23-cm length of tubing to 28.8 micrograms/mL using the entire (185-cm) tubing. Also, the percentage of diazepam adsorbed to the tubing increased as the infusion time decreased. A biexponential equation based on the adsorption data obtained for various tubing lengths was successfully used to calculate the percentage of the theoretical diazepam dose delivered through the tubing during different infusion times. To minimize the adsorption of diazepam to PVC administration sets, the shortest possible length of administration-set tubing should be used.(ABSTRACT TRUNCATED AT 250 WORDS)

MeSH terms

  • Adsorption
  • Diazepam / administration & dosage*
  • Diazepam / analysis
  • Infusions, Intravenous / instrumentation*
  • Polyvinyl Chloride / analysis*
  • Polyvinyls / analysis*
  • Spectrophotometry, Ultraviolet


  • Polyvinyls
  • Polyvinyl Chloride
  • Diazepam