The effect of morphine on phagocytosis of peritoneal phagocytes of mice

Background: There are reports about the increase of severity of infections in patients receiving morphine. Therefore this study was aimed to evaluate the effect of morphine on phagocytic activity of peritoneal phagocytes of mice.

Methods: Fifty six female Balb/c mice, 6-8 weeks old and 28±2 gram weight, were divided into two groups. The case group received 20, 40, 60 and 80 mg/kg morphine on first, second, third and fourth days, respectively, in the morning and evening, and 100 mg/kg (0.5 cc) once a day on days 5 to 10. Control group received 0.5 cc normal saline at the same time. Then, the mice were killed on days 3, 5 and 10. The peritoneal contents aspirated and mixed with sheep red blood cells (SRBC). Ultimately, the number of phagocytes that engulfed SRBC was determined with light microscope, and compared in two groups.

Results: The number of phagocytes engulfed SRBC in case group was significantly less in the tenth day (the third stage of experiment) in comparison with that of control group (P<0.031).

Conclusion: Prolonged administration of morphine (ten days) decreases the activity of peritoneal phagocytes in Balb/c mice. Therefore, it should be used with caution in patients in whom immune suppression is hazardous or use alternative drugs instead.