Pfizer (NYSE:PFE) posted respectable second-quarter earnings yesterday, but whether it'll keep up the pace in the quarters to come is anyone's guess.

In the first quarter of the year, Pfizer took a large hit from generic competition, watching revenue and earnings numbers decline year over year. But thanks to a weakening dollar and some aggressive cost cutting, Pfizer turned things around this quarter. The company's revenue grew 9%, while adjusted net income rose 26% year over year.

In fairness, Pfizer took its lumps in years like 2005, when a strong dollar pinched its earnings, without complaining or switching to "constant currency" valuation metrics to distort its financial picture. Still, it's hard not to notice that the biggest constituent of Pfizer's revenue growth this quarter was a seven-percentage-point contribution from changes in the dollar relative to other currencies like the euro. Without this currency benefit, Pfizer would have posted revenue growth of only 2% this quarter year over year. That's much better than Pfizer's 5% year-over-year decline in revenue in the first quarter, but it's still nothing to get excited about.

Even excluding the powerful force of currency effects, Pfizer's lead drug Lipitor did regain some traction. The drugmaker managed to stem hemorrhaging sales of this cholesterol-lowering drug against rivals made by AstraZeneca (NYSE:AZN), Abbott Labs (NYSE:ABT), and Schering-Plough (NYSE:SGP), and generic copies of Merck's (NYSE:MRK) Zocor. Combining this with the continued bad news coming from some rival therapies, and Pfizer's efforts to shore up its patent estate, it was a pretty good quarter for Lipitor.

Nobody expects Pfizer to be a growth stock anymore, nor even post much top-line growth. That made this quarter's top-line growth numbers and even better net income gains such a surprise to observers like me. To be clear, though, this was probably a one-time benefit from cost-cutting and a weak dollar; don't expect such gains to repeat themselves.

All the same, investors on both sides of the Pfizer bull and bear arguments can make good cases for the drugmaker's near-term prospects. Get ready for some volatile times for Pfizer's shares until its future clear ups one way or another.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has an A+ disclosure policy.