Rahway-based Merck announced Thursday that the U.S. Food and Drug Administration has approved Lipfendra, the first once-daily oral PCSK9 inhibitor to help lower LDL, or “bad,” cholesterol in eligible adults with high cholesterol, including some with an inherited form of the condition.

The prescription medication is approved as an addition to diet, exercise and other cholesterol-lowering treatments for adults who need further reductions in LDL cholesterol. Until now, PCSK9 inhibitors have only been available as injectable medications.

Merck said the approval was based on two Phase 3 clinical trials involving adults with high cholesterol. After 24 weeks, patients taking Lipfendra saw LDL cholesterol levels fall by 56% and 59%, respectively, compared with a placebo.

High LDL cholesterol is a major risk factor for cardiovascular disease, which can lead to heart attacks and strokes. While Lipfendra has been shown to significantly lower LDL cholesterol, Merck said an ongoing study is evaluating whether the drug also reduces the risk of cardiovascular events.

The company said the most common side effects seen in patients with inherited high cholesterol were diarrhea and dizziness. Overall, the drug’s safety profile was similar to placebo in the larger clinical trial.

Merck said the approval marks the first FDA-authorized oral PCSK9 inhibitor, giving patients another option for managing high cholesterol with a once-daily pill instead of injections.