U.S. imports of four generic drug classes tracked by Panjiva fell 9% on a year earlier in April. That was the fourth straight drop and brought the quarterly decline to 12%. That may reflect uncertainties among institutional buyers about the future American Health Care Act. Import growth, and resulting inventory increases, in late 2016 may also be to blame. Shipments of omeprazole, and its derivatives, fell 35% after the launch of the generic version of Zegerid. A similar phenomenon can be seen in anticonvulsants after Dr. Reddy’s started sales of lamictal in October. The generic drugmake...