PHILADELPHIA — A federal judge has denied Johnson & Johnson’s request for a preliminary injunction barring Amgen Inc. from offering discounts on certain drugs to treat side effects of chemotherapy, which J&J blames for declining sales of its anemia drug.

But J&J, of New Brunswick, N.J., said yesterday it still plans to pursue a full trial in the case. J&J argues Amgen’s discounts have hurt sales of Procrit, which treats chemotherapy-related anemia in cancer patients.

J&J has licensed Procrit from Amgen since the 1980s. Amgen sells the same drug under the brand Epogen, but under an agreement with J&J, Amgen only sells Epogen to treat anemia in kidney-dialysis patients, while J&J sells it in non-dialysis settings.

Amgen, with headquarters in Thousand Oaks, Calif., and a manufacturing plant in West Greenwich, also sells a newer drug, Aranesp, to treat anemia in both dialysis and chemotherapy patients, thus competing directly with J&J’s Procrit in chemotherapy settings.

To spur sales, Amgen offers cancer clinics discounts if they purchase certain amounts of Aranesp and two other Amgen chemotherapy-related drugs, Neupogen and Neulasta, which are designed to boost white blood cell counts and ward off infections. Partly as a result, Aranesp sales have taken off and gained market share from Procrit, rising 27 percent to $1.1 billion for the third quarter.

J&J sales of Procrit and Eprex — the brand name it’s sold under in Europe — fell 5.3 percent to $2.4 billion for the third quarter.