Sales of Amgen's (Nasdaq: AMGN) anti-infection drugs helped its first-quarter profits, but unfortunately couldn't help stop the infection of health-care reform adjustments that have hit most drugmakers this earnings season.

Sales of Neulasta and Neupogen, which boost cancer patients' immune systems, were up 10%. Revenue from U.S. sales increased 8% because of an increase in price and the inventory buildup by wholesalers. International sales increased 9% in constant dollars as patients switched from the older Neupogen to Neulasta and Amgen expands into additional territories. Exchange rates tacked on an additional 5% to international growth for these drugs.

The rest of Amgen's offerings also looked solid. Worldwide sales of anemia drugs Aranesp and Epogen didn't go down, which is a good thing after all the turmoil they've been through. Enbrel sales only increased 6%, which is slower than the overall growth of Abbott Labs' (NYSE: ABT) Humira and Johnson & Johnson (NYSE: JNJ) and Merck's (NYSE: MRK) Remicade, but Amgen only books sales in the U.S. and Canada. We'll have to wait until Pfizer (NYSE: PFE) reports to see how Enbrel is growing internationally.

Like every drugmaker I've looked at so far this earnings season, Amgen announced a decrease to its earnings because provisions in the health-care reform bill require drugmakers to offer larger discounts to Medicaid. In total, the changes will cost the company $200 million to $250 million this year. Amgen didn't lower guidance, but did say that it now expects to come in toward the lower end because of the new rules.

Where on that lower end of the adjusted earnings of $5.05 to $5.25 per share depends on how well the launch of its osteoporosis drug, Prolia, goes. Amgen resubmitted the application earlier this year and expects to hear back from the Food and Drug Administration in late July. Last year's rejection was mostly paperwork-driven, so an approval seems likely on its second try.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.