Protein binding of piritramide: influence of various protein concentrations and the postoperative acute phase response

Abstract

Objective: Piritramide is a lipophilic opioid, which is widely used for postoperative analgesia and analgosedation in Europe. In this study we investigated the influence of various protein concentrations (total protein, ₁-acid glycoprotein, albumin) and the postoperative acute phase response on the protein binding of piritramide.

Methods: The influence of various protein concentrations on the protein binding of piritramide was investigated by either diluting the serum samples of five volunteers with isotonic saline or by adding different amounts of ₁-acid glycoprotein. Albumin binding was measured in a 5% human albumin solution. The impact of the postoperative acute phase response was investigated by obtaining daily serum samples from 18 surgical patients until the third postoperative day, and measuring piritramide protein binding, ₁-acid glycoprotein, total protein and albumin.

Results: There was a significant relationship between piritramide protein binding and the concentrations of total protein and ₁-acid glycoprotein. The binding to albumin was 88%. During the postoperative acute phase response, the protein binding of piritramide did not change. Serum concentrations of ₁-acid glycoprotein increased, whereas total protein and albumin decreased.

Conclusion: Although there were significant changes in the piritramide-binding proteins, ₁-acid glycoprotein and albumin, during the postoperative acute phase response, the protein binding of piritramide did not change. Therefore, a change in protein binding, which might be one factor to be considered in determining piritramide dosage in the postoperative period, does not have to be taken into account.