Background & objectives:
Antidepressants are being used as analgesics for various pain related disorders like neuropathic and non neuropathic pain. Although their analgesic activity is well recognized but anti-inflammatory potential of antidepressants is still inconclusive. Since the antidepressants are used for longer duration, it becomes important to elucidate effect of anti-depressants on blood pressure and gastric mucosa. This study was undertaken to evaluate the anti-inflammatory potential of various antidepressant drugs as well as their effect on blood pressure and gastric tolerability on chronic administration in rats.

Methods:
Rat paw oedema model was used for studying anti-inflammatory activity, single dose of test drug (venlafaxine 20 and 40 mg/kg, amitryptline 25 mg/kg, fluoxetine 20 mg/kg) was administered intraperitoneally 45 min prior to administration of 0.1 ml of 1 per cent carrageenan in sub-planter region. Oedema induced in test group was compared with normal saline treated control group. For studying effect on blood pressure and gastric tolerability, test drugs were administered for 14 days. Blood pressure was recorded on days 0, 7 and 14 using tail cuff method. On day 14, 4 h after drug administration, rats were sacrificed and stomach mucosa was examined for ulcerations.

Results:
Pretreatment of rats with venlafaxine (40 mg/kg) resulted in a significant decrease in paw oedema as compared to control (2.4 ± 0.15 to 1.1 ± 0.16 ml, P<0.01). Similarly, in the group pretreated with fluoxetine, significant decrease in paw oedema was observed in comparison to control (P<0.05). Significant change in mean blood pressure was seen in rats pretreated with venlafaxine 40 mg/kg (126.7 ± 4.2 to 155.2 ± 9.7, P<0.05) and fluoxetine (143.5 ± 2.6 to 158.3 ± 1.2, P<0.05) on day 7. No significant difference with regard to gastric tolerability was observed among groups.

Interpretation & conclusions:
Our findings showed significant anti-inflammatory activity of venlafaxine (40 mg/kg) and fluoxetine but these drugs were also associated with an increase in blood pressure. No significant change in mean ulcer index was observed among groups.