Preclusion of methemoglobinemia caused by nitrate drugs in diabetics and nondiabetics: Possible role of Vitamin C.

The drugs containing nitrates like isosorbide dinitrate, isosorbide mononitrate and glyceryl trinitrate, etc., trigger the oxidation of hemoglobin which is manifested in the pathological disorder named methemoglobinemia. It was considered interesting to investigate the preventive roles of vitamin C towards the toxic effects of nitrate containing drugs used for the treatment of angina. The aim is to find whether these drugs need to be administered with special care to diabetic patients who are more prone to develop methemoglobinemia. Vitamin C (500 mg/day) was administered orally to reduce the methemoglobin (metHb) level in both the diabetic and nondiabetic patients consuming nitrate containing drugs regularly, keeping diabetic and nondiabetic patients not on nitrate drugs as control. Concentration of metHb and hemoglobin A (HbA) was estimated spectrophotometrically assuming the molar extinction coefficient values of metHb as 3.78 mM ^{- -1}  cm ^{- -1} at 630 nm and HbA as 125,000 M ^{- -1} cm ^{- -1} at 415 nm. MetHb level was found to be lower after the treatment with vitamin C for 30 consecutive days than that before the trial with statistically significant two tailed p value. Additionally, fasting insulin level was also found to decrease after 4 weeks of consumption of vitamin C with moderate lowering of fasting serum glucose level as well, indicating a higher insulin sensitivity for the treated patients.
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