Abstract: AIM: To evaluate the effects of cough induced by equivalent doses of alfentanil and fentanyl. METHODS: Fifty patients undergoing general anesthesia were randomly assigned to alfentanil group ,and fentanyl group.Two groups were received equivalent doses of alfentanil 8 μg/kg, and fentanil 2 μg/kg, via IV push within 5 seconds respectively. To observe the starting time ,incidence and severity of cough, heart rate (HR) and mean arterial pressure (MAP) were recorded immediately before injection (T₁) and 2 min (T₂) after injection. RESULTS: Alfentanil group had an earlier starting time than fentanyl group. alfentanil group had a significantly lower incidence of cough than fentanyl group(P<0.05). Compared with T₁, the HR and MAP of alfentanil group and fentanyl group at T₂ were significant lower(P<0.05).Compared with fentanyl group, the extent of decrease in the HR and MAP of alfentanil group were significant higher(P<0.05).CONCLUSION: Alfentanil induces a lower incidence of cough and more steadier circulation than equivalent doses of fentanyl.

Key words: Cough, Alfentanil, Fentanyl