When Pfizer (NYSE:PFE) reported its first-quarter results in May, there were things to like -- but things to dislike, too. The big pharma company's earnings soared and topped Wall Street expectations. Revenue, however, came in lower than the consensus analysts' estimate.

What should investors expect when Pfizer announces its second-quarter earnings results on July 31? I suspect the drugmaker's numbers might be weaker than you'd like them to be. Here are three reasons why.

Needle on gauge pointing near unhappy face on left with happy face on right and a question mark in the middle of the gauge

Image source: Getty Images.

1. Same old headwinds will still be blowing

Pfizer's biggest challenges in the first quarter came from declining sales of products that have lost exclusivity and continued product shortages with its sterile injectables business. Don't count on improvement on either of these fronts.

It wouldn't surprise me if these headwinds hurt Pfizer even more in Q2 than they did in Q1 because of Viagra. Last year, the erectile dysfunction drug made more revenue in the second quarter than it did in the first quarter. Pfizer reported a 45% year-over-year decline in sales in its last quarter following Viagra's loss of exclusivity at the end of 2017. I think the year-over-year drop could look even worse when the company announces its Q2 results.

Those sterile injectables product shortages probably won't get any better, either. In Pfizer's Q1 conference call, COO Albert Bourla said that the company expected sales to fall again in the second quarter. 

2. Question marks for key blockbusters

The top three growth engines for Pfizer right now are Ibrance, Eliquis, and Xeljanz. However, in the first quarter, sales growth for both Ibrance and Xeljanz was slower than analysts projected. The big question for Pfizer in Q2 is whether these blockbuster drugs will deliver growth at expected levels.

When asked about the relative underperformance in Q1 for Ibrance, Pfizer CEO Ian Read replied that the company thought that it was due to "inventory movements." In his introductory comments during the Q1 conference call, Read said that revenue for both Ibrance and Xeljanz were negatively impacted by "customer buying patterns." I believe these explanations are correct and could be lesser issues in the second quarter.

At the same time, though, I wouldn't discount the possibility that Pfizer's growth could be affected by competition from newer products on the market. Eli Lilly, for example, recently reported Q2 sales of nearly $58 million for breast cancer drug Verzenio. Novartis announced that its breast cancer drug Kisquali generated sales of $59 million in the second quarter. Both Verzenio and Kisquali compete directly against Ibrance.

3. Fewer one-time boosts than in Q1

There's one area where Pfizer is almost guaranteed to see a worse performance in the second quarter than it did in Q1. The company's other income in the first quarter was around $320 million, but Pfizer projects total other income in 2018 of $400 million. It's a mathematical certainty that Q2 other income will be lower if Pfizer's full-year estimate is accurate.

This large amount of other income in the first quarter stemmed primarily from one-time milestone payments of around $115 million and $110 million in unrealized gains on equity securities. In the second quarter of 2017, Pfizer had $66 million in other income. Unless the company records nearly all of the remaining other income it expects for the rest of 2018 in Q2, both year-over-year and quarter-over-quarter comparisons will be negative. 

This isn't a huge deal. However, a few million here and a few million there can add up. With continued challenges from sinking sales for drugs that have lost exclusivity and sterile injectables product shortages, along with uncertainties for Ibrance and Xeljanz, fewer one-time boosts could make a difference in whether Pfizer meets or misses Q2 estimates. 

But better days lie ahead

It might sound like I'm down on Pfizer, but I'm not. I think the company could announce disappointing second-quarter results -- although there's at least an outside chance of a pleasant upside surprise. However, whatever Pfizer reports in Q2 probably won't matter much in the big scheme of things.

What really matters for Pfizer is its long-term prospects. I'd argue that the big pharma company looks pretty good on that score. The negative issues that Pfizer faces right now should become less of a drag over the next few years. The company's pipeline is probably more promising than it's ever been. In the meantime, Pfizer continues to generate strong cash flow and keeps on paying a dividend that should bring smiles to investors' faces.

Sure, there are things to dislike about Pfizer. Some of those things will likely be quite evident when the company provides its second-quarter update. But I think there's a lot more to like about this stock over the long run than there is to dislike.