The Senate Caucus on International Narcotics Control was created to “monitor and encourage United States Government and private programs seeking to expand international cooperation against drug abuse and narcotics trafficking” and to “monitor and promote international compliance with narcotics control treaties.” As a formal organization of the U.S. Senate, the Caucus has the status of a standing committee. The Caucus exercises oversight on a wide range of issues, including international counternarcotics assistance and domestic drug prevention and treatment programs. The Caucus has held numerous hearings over the years and has issued a number of reports on U.S. narcotics control policy. (source)
The chair is always selected from the majority party and the ranking member is the most senior member of the minority party.
The majority party ensures it has a majority on every committee.