Raymond Gilmartin, chief executive of Merck, will testify before a Senate committee next week on the withdrawal of Vioxx, in spite of efforts by the drug company to send others in his place.

Thursday's hearing has been arranged by the Senate finance committee to investigate Merck's response to safety concerns about the painkiller before its withdrawal from the market. Also under scrutiny will be the role of the Food and Drug Administration, the industry regulator.