Meloxicam prevents COX-2-mediated post-surgical inflammation but not pain following laparotomy in mice

BackgroundInflammation is thought to be a major contributor to post-surgical pain, so non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used analgesics. However, compared to rats, considerably less is known as to how successfully these prevent pain in mice. MethodsA fluorescent COX-2 selective probe was used for the first time to evaluate the post-surgical anti-inflammatory effects of meloxicam, and automated behaviour analyses (HomeCageScan; HCS), the Mouse Grimace Scale (MGS) and body weight changes to assess its pain-preventative properties. Groups of 8-9 BALB/c mice were subcutaneously injected with saline (0.3mL) or meloxicam at (1, 5 or 20mg/kg) 1h before a 1.5-cm midline laparotomy. The probe or a control dye (2mg/kg) was injected intravenously 3h later. Imaging was used to quantify inflammation at 7, 24 and 48h following surgery. HCS data and MGS scores were respectively obtained from video recordings and photographs before surgery and 24h later. ResultsPost-surgical inflammation was dose dependently reduced by meloxicam; with 5 or 20mg/kg being most effective compared to saline. However, all mice lost weight, MGS scores increased and behavioural activity was reduced by surgery for at least 24h with no perceivable beneficial effect of meloxicam on any of these potentially pain-associated changes. ConclusionsAlthough meloxicam prevented inflammation, even large doses did not prevent post-laparotomy pain possibly arising due to a range of factors, including, but not limited to inflammation. MGS scoring can be applied by very naive assessors and so should be effective for cage-side use.