A solid first-quarter performance wasn't enough to provide a big rebound for CVS Health (NYSE:CVS) stock. The pharmacy giant's share price is down 10% so far in 2018. 

But CVS Health announces its second-quarter results before the market opens on Wednesday, Aug. 8. Could the news translate to a positive catalyst for the beaten-down stock? Maybe, but I wouldn't count on it. Here are three things you should probably expect in the company's Q2 earnings update.

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1. Slowing revenue growth

CVS Health's revenue grew by 2.6% year over year in the first quarter. The pharmacy company is likely to report more sluggish revenue growth in its Q2 results for several reasons.

Probably the biggest factor is the calendar. CVS Health's stores typically enjoy a sales boost in the days leading up to Easter. In 2017, Easter fell on April 16. This year, however, Easter was on April 1. That means CVS Health's Easter-related sales will be significantly lower in Q2, dragging down the company's overall revenue growth.

Sequential revenue growth will also probably fall off. The cold and flu season was especially nasty this year. While that was bad for patients, it was good for CVS Health. The company's retail pharmacies and MinuteClinic walk-in clinics experienced a surge in revenue. However, the cold and flu season was over in the second quarter, translating to lower revenue growth compared with the previous quarter. 

In addition, CVS Health will almost certainly continue to face ongoing challenges for its Omnicare and pharmacy benefits management (PBM) businesses. In CVS Health's Q1 conference call, CFO Dave Denton stated that the company's "long-term care Omnicare business is not performing as we expected." Many long-term care facilities are struggling financially. CVS Health's PBM unit is experiencing price compression and a negative revenue impact from the introduction of new generic drugs. 

2. Sustained earnings growth fueled by tax reform

While revenue growth in the second quarter could be anemic, CVS Health earnings should continue to enjoy strong year-over-year earnings growth. There's one big reason earnings are improving: a huge impact from U.S. corporate tax reform.

CVS Health's guidance provided in May called for adjusted earnings per share (EPS) in Q2 of between $1.59 and $1.64. The midpoint of that range reflects a year-over-year increase of 21%. Wall Street's consensus adjusted EPS estimate for the second quarter is $1.61, right in the middle of the guidance range. 

In the first quarter, CVS Health's GAAP net income increased by $45 million. But the company stated that its lower tax rate contributed an additional $100 million to its bottom line. It's likely that there will be a similar result in Q2, with earnings growth coming entirely -- or close to it -- from U.S. corporate tax reform.  

3. Weaker Q3 earnings outlook

One of the biggest things investors look at with CVS Health's quarterly update is the company's guidance for the next quarter. I suspect CVS Health's Q3 earnings outlook will reflect weaker growth than we'll see in its second quarter. There are two reasons Q3 earnings could be weighed down. Both of them relate to the timing of CVS Health's spending. 

The company has consistently stated that it plans to invest some of the tax savings that it's getting thanks to corporate tax reform back into the business. CVS Health committed to reinvesting $275 million of these tax savings in 2018. However, most of that amount will be spent in the second half of the year. 

Another reason CVS Health's spending will be higher starting in Q3 is the ramp-up of activities related to the Anthem implementation. CVS Health's PBM contract with Anthem becomes effective in 2020. The company expects to spend around $150 million on the implementation of the new business, with most of the costs in the second half of 2018.

Beyond the numbers

Two subjects are almost certain to come up quite a bit during CVS Health's conference call that aren't directly related to its Q2 results. One is the progress on the planned acquisition of Aetna. CVS Health still anticipates that this deal will close in the second half of the year.

The other hot topic likely to be discussed is the prospect of U.S. drug pricing reform. The Trump administration has targeted drugmakers' practice of providing rebates to PBMs. Some critics have accused PBMs of pocketing much of the rebate money to pad their profits. CVS Health has stated in the past that it returns around 90% of rebates to payers, but Dave Denton said in the Q1 conference call that the figure is now "probably a lot closer to 95%."

Both the pending Aetna acquisition and potential rebate changes in the U.S. contribute to uncertainty for CVS Health -- as do the prospects of new competition from Amazon.com. Even if the company delivers a pleasant surprise with its Q2 earnings results, it probably won't reduce the level of uncertainty about CVS Health's future.