When you think of Johnson & Johnson (JNJ 0.64%), you may think of shampoo and Band-Aids. But those products are in J&J's consumer health business -- and they're not the company's biggest revenue drivers. In fact, J&J is in the process of spinning off that business into an entity called Kenvue.

What is J&J's top revenue driver? It's the company's pharmaceuticals business, which brought in more than $52 billion in sales last year. And the crown jewel of that business is immunology drug Stelara.

But that may not be for long. A key patent is set to expire this year -- and J&J recently settled a lawsuit allowing a challenger to soon enter the market. Here's what you need to know.

Stelara's billion-dollar revenue

First, a bit of detail about Stelara -- the product that generated $9.7 billion in sales last year. The immunology drug treats plaque psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis. Stelara calms an overactive immune system by blocking the function of two proteins. This reduces the inflammatory process that triggers the symptoms of these illnesses.

Since Stelara is a biologic made from living cells, rivals can't copy it 100% -- in the way that a generic copies a traditional drug. But that doesn't mean biologics are free from the risk of competition. Rivals can produce biosimilars, which are "highly similar" to the original product, according to the U.S. Food and Drug Administration (FDA).

This is what happened in the case of Stelara. A few players are working on biosimilar candidates. But the focus right now is on Amgen (AMGN 1.22%).

J&J recently settled its lawsuit regarding an Amgen candidate that aims to compete with Stelara. The settlement allows Amgen's potential product to enter the market "no later than January 1st, 2025," according to Reuters. Meanwhile, J&J mentioned in its earnings calls that it expects its Stelara composition of matter patent to expire later this year in the U.S.

The experience of Remicade

J&J has been through the loss-of-exclusivity situation before. Its immunology drug Remicade faced this challenge a few years ago. In fact, J&J recently settled a class action suit alleging the pharma company took steps to make it difficult for biosimilars to compete with Remicade.

Last year, Remicade sales fell 26%. And the product's sales slipped about 14% in each of the previous two years.

J&J predicts a "steeper erosion curve" for Stelara, compared with Remicade.

J&J faces the loss of exclusivity on an important revenue driver. Stelara represented more than 18% of J&J's pharmaceutical sales last year. But the upcoming loss isn't a surprise, and J&J has been preparing for the situation. In its recent guidance for the year, J&J assumed Stelara would lose exclusivity in the third or fourth quarter.

Still, J&J is optimistic that current blockbusters and candidates in the pipeline will keep growth going. The big pharma company has 30 products/platforms that bring in more than $1 billion in annual revenue. J&J predicts "above-market growth" this year in its pharmaceuticals division, even considering the Stelara situation.

It's important to note that a significant drop in Stelara revenue probably won't happen overnight. The FDA hasn't even issued a decision on Amgen's biosimilar yet. That's expected in the second or third quarter of this year, Fierce Pharma reported, citing the lawsuit.

The role of consumer health

Meanwhile, J&J is progressing with its spinoff of the consumer health business. This has been the company's slowest-growing unit and has contributed less to revenue than pharmaceuticals and medtech. So the spinoff should boost J&J's overall growth -- and help the company focus on its strongest businesses.

This idea of focus is key if J&J aims to limit the impact of the Stelara loss of exclusivity and reach long-term revenue goals. Right now, J&J predicts pharmaceuticals revenue will climb 10% to 15% by 2025, depending on currency fluctuations.

All of this means that, yes, the Stelara loss represents a challenge ahead. But it's an expected one -- and something all pharma companies face at a certain point.

J&J's great number of other blockbuster products and platforms and its pipeline candidates indicate growth isn't over. And the consumer-health spinoff should offer another burst of energy to the company.

That's why J&J is likely to keep its promise to grow beyond Stelara -- and that may equal share performance growth for long-term investors, too.