* Amgen Inc. said it earned $60...

* Amgen Inc. said it earned $60 million, or 41 cents per share, in the fourth quarter ended Dec. 31, contrasted with a year-earlier loss of $28 million, or 24 cents per share, that resulted from a one-time $50-million charge.

Revenue more than doubled from a year earlier, to $210 million from $91.2 million, on the success of two drugs that the Thousand Oaks biotechnology firm has been marketing--Epogen, which treats anemia in patients with kidney disease, and Neupogen, which helps fight infection in chemotherapy patients.

For all of 1991, Amgen earned $97.9 million, compared to $3.9 million the previous year, and its annual revenue more than doubled, to $682 million. Earnings per share for all of 1991 totaled 67 cents, up from 3 cents in 1990. The 1991 results included a onetime pretax charge of $129 million assessed against Amgen in an arbitration ruling stemming from a dispute over the marketing of one of its drugs. Excluding that charge and the $50-million charge in 1990, which stemmed from Amgen’s buyout of future royalties, the company said it would have earned $186 million last year and $56 million in 1990.