Health-care mergers—already under scrutiny from regulators and House lawmakers—are about to get some additional attention from the Senate.

The Senate Judiciary Committee’s antitrust panel plans to hold a hearing on vertical health-care mergers in June, a spokesman for Chairman Mike Lee (R-Utah) told Bloomberg Law May 13. Vertical mergers involve companies in different parts of the same industry.

The hearing comes less than a year after the Justice Department approved two mega-mergers in the industry, CVS Health Corp.-Aetna Inc. and Cigna-Express Scripts, deals that totaled $137 billion.

The three largest pharmacy benefit managers—CVS Caremark,...