The rupee dropped to one-and-half month low of 54.25 against US dollar before regaining some ground today amid persistent demand for the American currency from banks and importers as it made gains in the overseas forex markets. The rupee opened lower at 54.10 per dollar as against the last weekend's level of 53.81 at the Interbank Foreign Exchange (Forex) Market and dropped further to about 6-week low of 54.25. Later, it quoted at 54.13 a dollar.