Amgen (AMGN) - Get Report  reported strong earnings Tuesday for both the fourth quarter and 2018 as a whole, but fell in after-hours trading anyway after issuing what Wall Street saw as a disappointing 2019 outlook.

The California-based biotech giant lost some 2.6% to $187.10 shortly after 6 p.m. ET. Earlier in the day, AMGN added 16 cents to end the regular session at $192.11, up 0.8% on the day. But on Monday, Amgen tumbled 3.4% following a downgrade from Evercore ISI, which cut the stock to "In-Line" from a previous "Outperform." 

Amgen returned to those losing ways in after-hours action Tuesday after the company projected 2019 full-year revenues at $21.8 billion to $22.9 billion and earnings per share at $13.10 to $14.30. That fell below analysts' previous expectations.

"Amgen's 2019 guidance looks light compared to the consensus estimate," said Jeff Marks, senior portfolio analyst with Jim Cramer's Action Alerts PLUS club for investors. He noted that Cramer's charitable trust sold some AMGN shares last week, which appears to have been a good move.

"This forecast confirmed the decision we made last Tuesday, when we downgraded our rating and sold shares when the stock traded slightly above $200," Marks said. (To read the full report on why Action Alerts PLUS reduced its Amgen stake, click here.)

Amgen's disappointing 2019 guidance stood in sharp contrast with the company's impressive fourth-quarter earnings numbers, which also came out Tuesday after the bell. AMGN said that strong sales of its cholesterol and cancer drugs helped push quarterly revenues up 7% to $6.2 billion.

All told, the company earned $3.42 per share in the quarter -- an 18% jump from the same period a year earlier. That beat analysts' consensus estimates of $3.26 in EPS, according to Zacks Investment Research. Operating income also increased 6% to $2.7 billion, while total product sales jumped 8% year over year.

For 2018 as a whole, Amgen earned $14.40 in EPS, a 14% rise from 2017. Operating income also gained 2% to $11.9 billion, while total 2018 product sales grew 3%.

Drugs that powered the gains included cholesterol medication Repatha, whose sales increased 62% for the fourth quarter and 72% for the year as a whole. Similarly, Blincyto, a treatment for a type of post-chemotheraphy leukemia, saw sales rise 37% for the quarter and 31% for the year.

Cancer drugs Xgeva and Kyprolis, osteoporosis treatment Prolia and clotting medication Nplate were also big sellers. Top money-makers Enbrel, an arthritis medication, and Neulasta, an infection-fighting drug for people fighting cancer, also performed better than expected, although sales fell in 2018 compared to the year prior.

Amgen is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells the stock? Learn more now.