A severe shortage of a drug used to treat childhood leukemia appears to be easing, lessening the risk that hundreds if not thousands of children might die from a curable disease. This close call and continuing shortages of other vital drugs again highlight why Congress must pass legislation giving the Food and Drug Administration more power to head off such crises.

Some 180 medically important drugs — most of which are injected in hospital, clinics and doctors’ offices — have been in short supply over the past year. This latest shortage involved a drug known as preservative-free methotrexate, which is injected into the spinal fluid to treat acute lymphoblastic leukemia in young children. The preservative can cause paralysis and thus cannot safely be used.

Like many other such shortages, this one was caused by manufacturing problems at one of the few plants still making the drug. One of the nation’s largest suppliers of methotrexate suspended operations at a plant in Ohio in November because of production and quality concerns. Supplies of the drug subsequently dwindled to the point that major hospitals were close to running out.

The shortage should ease in a couple of weeks because the manufacturer, Ben Venue Laboratories, will release supplies made before its plant shut down and three other manufacturers have agreed to increase their production at the request of the F.D.A.