The Sensex at the Bombay Stock Exchange dropped 186 points, or 1 percent, to 18,345, on renewed inflation and interest rate concerns, and in line with weak global markets, today. The Nifty at the National Stock Exchange slipped 46 points, or 0.8 percent, to 5,499.Stock markets in Japan, China, Hong Kong, South Korea and Singapore lost between 0.8 percent and 1.4 percent.