Equity benchmark Sensex dropped over 150 points in opening trade on Wednesday, tracking losses in index majors Reliance Industries, HDFC Bank and Kotak Bank amid a negative trend in global markets. The market, however, turned flat in the first half hour of trading. The 30-share BSE index was trading 6.73 points or 0.01 per cent higher at 50,200.06, and the broader NSE Nifty advanced 1.50 points or 0.01 per cent to 15,109.60.