Big pharmas are scrambling to get the most expensive medications off the shelf and into pharmacies across the country.

But one of the biggest challenges facing pharmacy chain Walgreens, the nation’s largest drugstore chain, is a shortage of its most expensive drugs.

“We’re seeing a very serious shortage of generic medicines,” Walgreen’s chief medical officer, Dr. James J. Mrazek, told CNBC on Tuesday.

“The availability of generic drugs has been one of our main strengths in the last few years, but we have a problem right now.”

What’s happening is that generic is being used in hospitals across the United States.

And we have to have a solution to get that going.

“Walgreens said it has been able to make some breakthroughs in the past couple of years to solve the problem.

For instance, it’s used its own proprietary pharmacy inventory to get drugs onto the shelves of Walgens, and its supply chain is improving as a result.

But for many other pharmacies, it may take several years to get their drugs onto shelves.

So for now, Walgrees customers will have to rely on generic.”

It’s going to be really hard for many people to find what they’re looking for,” Mrazeks said.”

In some cases, you’re going to need to go back to the pharmacy to get it.

“So Walgends customers who want to get generic are going to have to make do with cheaper generics from companies like Teva and Novartis.

But the bigger problem is the supply chain, which is broken, according to Mrazeeks.”

For the last two years, we have been able at the chain level to bring in generic drugs for a lot less money than the manufacturer is paying us to do so,” he said.

While the situation is not as bad as it used to be, Walnuts pharmacy staff said they have a hard time finding enough supplies.

They said they often have to buy supplies from private businesses.

In the past year, Walons drugstore has been facing a shortage.

Last year, the chain was forced to order a lot of generic medicine from a third-party company to get enough medicine on its shelves.

And that forced Walgons to lower its prices, from about $1 to $1.50 per pill.

It’s also been hit with a massive price hike.

For this year, it will be selling about 20 times as many generic drugs, including about two dozen generic drugs that cost up to $2,500.”

That’s a lot more expensive than what they were charging before,” said pharmacy manager Michelle Smith.

And Walgos price hike, combined with the supply shortage, has forced the chain to raise prices even more.

The company said it will now start selling drugs that are up to half the price of generic.

But Walgros prices are still a fraction of those of generic drugstores.”

So we have really limited capacity to get medications off shelves and onto our shelves.””

The cost of a generic is about $5 a pill, but if you’re getting a generic that costs $1, you can’t afford to spend that much money on that.”

So we have really limited capacity to get medications off shelves and onto our shelves.

“The supply chain also is a problem for Walgarts customers.”

Some of the generic that’s out there is very expensive and that has really impacted our pricing,” Smith added.

Mrazeks also said Walgashes drugstore will continue to be the most efficient in the country, but that may be changing.

He said Wals prices may start dropping in the next few years.

The problem is not just a Walgess problem, he said, but a pharmacy supply chain issue.”

If we can’t get our prices down, then what we really need is the generic,” Mraks said.

The American Health Care Act passed last week would create a new national drug supply chain to help alleviate shortages.

The drugmaker Merck, which makes some generic drugs as well as other drugs, has been negotiating with Walgops pharmacy.

Mraks noted that Walgys prices are up about 10% this year and he expects the price increases to continue.

But he said Walgets drugstore prices will continue their steady rise.”

Our pricing is going up every year, and that’s just going to keep going up, so it’s going up,” Mrs. Smith said, noting that Walgs price is also increasing at other pharmacies as well.

Mrs. Mrakes said Walges drugstore could see some new drugs added next year, but it’s not sure when they will be available.

Follow CNBC National Health Day on Twitter at @CNBCHealthDay