Zandu Pharmaceutical Works Ltd said on Wednesday its promoters have pledged 409,344 shares or 50.76 percent of its total equity base.
It did not say to whom they were pledged or for what purpose.
Personal care products maker Emami Ltd and its associates hold 70.34 percent stake in Zandu, post the open offer made last year.
Ahead of the news, shares in the company ended 2.35 percent lower at 4,881.50 rupees in the Mumbai market.