Maybe this has happened to you: you’re at the pharmacy, picking up a refill of a prescription that you or a family member have been taking for a long time. It’s a routine errand until you get sticker shock: the copay has suddenly shot up. You didn’t change insurance, it’s still the same year, and the drug is the same: how can a price change so dramatically so quickly?

Our colleagues down the hall at Consumer Reports heard about this phenomenon and investigated how widespread the problem is, and how to deal with sudden drug price spikes. They learned that drug prices have been rising dramatically in the last few years, especially for generics. Insurance plans normally place drugs on tiers according to how much they cost or simply don’t include them on the list of covered drugs (the “formulary”) at all, as CVS/Caremark recently did with Viagra and some other pricey brand-name medications.

An old, inexpensive drug that has been on the market for decades might be Tier I and have a very low copay or even none at all. More expensive drugs might be on higher tiers or not on the formulary at all. What’s been happening recently is that a drug will sometimes increase in price significantly with no warning.

“For whatever reason, raw material shortage or some other problem, literally overnight we’ll see a dramatic increase,” an independent pharmacist in Texas told Consumer Reports. Pharmacies pass the sudden cost increases on to their customers and to their insurance companies. Some generic drug prices have increased dramatically, like tetracycline, which increased from five cents per pill to $8.59 per pill in just a year.

Consumer Reports recently polled adults who take prescription drugs to find out whether this had happened to them. One-third of respondents said that it had. Most of them (81%) simply paid the higher price at the pharmacy because, well, they needed the refills. Some paid more than $100 per prescription out-of-pocket.

One example: a woman who doesn’t have insurance had to pay $500 for a three-month supply of hydroxychloroquine, a venerable drug for rheumatoid arthritis that used to cost about half that much. She didn’t have a choice, though, and paid the higher price.

After leaving the pharmacy, most people in the poll tried to manage the issue, contacting their insurance company to make sure there was no error, and checking with their health care provider to find out whether cheaper alternatives were available. For many people, a sudden spike in the cost of important medication means skipping payments on other bills or avoiding other medical care.

If this happens to you or to someone in your family, what can you do?

Review your medications: you may be able to drop or change some maintenance medications.

Check the formulary: It should be available on your health insurer’s website, and lists covered drugs and lower-cost alternatives.

Shop around: Check prices between different pharmacies and big-box stores. Some offer cheap generics that other chains don’t, or offer some categories of drugs with no copay as a loss leader to attract new pharmacy customers. Costco fills prescriptions for non-members, and you might find assistance or the lowest price in an unexpected place.

Are you paying more for your meds? [Consumer Reports]

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