Introduction: Indomethacin increases generation of mitochondrial reactive oxygen species (ROS) which have a crucial role in the indomethacin-induced gastric ulcer. Coenzyme Q10 has an antioxidant activity on mitochondria and cell membranes and protects lipids from oxidation and is essential for stabilizing biological membranes. Superoxide dismutase (SOD) acts as one of the defense mechanisms against free radicals. When the generation of ROS overwhelms, the antioxidant defense, lipid peroxiation of cell membrane occurs and cause cell damage.
Materials and Methods: Male adult Wistar rats were divided into A and B groups. The rats in group A were then further divided into three subgroups of 6 animals each and received one of the following treatments: Animals in the first subgroup received saline. Animals in the second subgroup received saline and indomethacin. Animals in the third subgroup received vitamin C and indomethacin. The rats in group B were also further divided into 3 subgroups of 6 rats each and treated with one of the following treatments: Animals in first subgroup received 1% Tween 80 as vehicle. Animals In second subgroup received 1% Tween 80 and indomethacin. Animals in third subgroup received CoQ10 and indomethacin. Four hours after the last treatment, animals were killed and the stomachs removed were cut and gastric mucosal lesions were examined). Ulcer indexes were determined and SOD activity measured in plasma                                                            
Results: Pretreatment with both vitamin C and coenzyme Q10 was associated with attenuation of ulcer index and increased SOD activity compared with animals treated with indomethacin alone (P<0.001).
Conclusion: This effect of CoQ10 may be due to its electron donating  property that inhibits the decrease in SOD activity in gastric tissue (replenishment of endogenous SOD) and inhibiting lipid peroxidation.