The antinociceptive effect of systemic administration of a combination of low-dose tramadol and dexmedetomidine in a rat model of bone cancer pain.

BACKGROUND

Multiple factors are involved in the mechanism of bone cancer pain. Treatment with a single drug is not adequate to target all of the different mechanisms.

OBJECTIVE

To study the analgesic effect of a combination of low-dose dexmedetomidine (DEX) and tramadol (TRA) on bone cancer pain in rats.

DESIGN

A randomised, controlled study.

SETTING

Central Laboratory of Shanghai Chest Hospital, Shanghai Jiaotong University, Shanghai China, from July 2011 to June 2012.

ANIMALS

Adult female Wistar rats weighing 180 to 200g.

INTERVENTIONS

Rats with bone cancer were divided into five groups based on drug treatment (n=12 for each group): T5 group (TRA 5 mg kg), T10 group (TRA 10 mg kg), D1 group (DEX 1 μg kg), T5+D1 group (TRA 5 mg kg+DEX 1μg kg) and IS (isotonic saline 0.5 ml) group.

MAIN OUTCOME MEASURES

The mechanical threshold and spontaneous paw withdrawal were measured in all groups.

RESULTS

Both the T5+D1 group and T10 group showed a significantly increased mechanical threshold and a lower incidence of spontaneous paw withdrawal compared with the IS group. Interestingly, there was no significant difference between the T5+D1 and T10 groups.

CONCLUSION

We found that a combination of DEX and TRA at low doses provided equal or superior analgesic effects on bone cancer pain compared to high-dose TRA alone. Our animal data might indicate the clinical administration of these two drugs in bone cancer pain therapy.