Abstract: AIM: To investigate the pharmacodynamic interactions between propofol and remifentanil by response surface methodology. The response surface for inhibition of somatic, hemodynamic responses to laryngoscopy and response surface of cardiovascular side effects were combined to identify the optimal combination of propofol and remifentanil. METHODS: Seventy ASA I-II patients were grouped randomly and parallelly. The patients received target-controlled infusion (TCI) of propofol (0-9 μg/mL) at a fixed concentration, then remifentanil was administrated with TCI device from 0 to 10 ng/mL in a stepwise ascending fashion. After reaching pseudo-steady-state drug levels, the somatic and hemodynamic responses to laryngoscopy and cardiovascular side effects were observed. The pharmacodynamic interactions were investigated by response surface methodology. RESULTS:Response surface models revealed significant synergy between propofol and remifentanil. Imax were 2.89, 5.02 and 2.55 for the somatic and hemodynamic responses to laryngoscopy and cardiovascular side effects. Based on the results of response surface method, the optimal dose range of propofol and remifentanil was constructed.CONCLUSION: Response surface method can analyze the pharmacodynamic interactions qualitatively and quantitatively and provide the optimal dose range.

Key words: propofol, remifentanil, drug interaction, response surface