It may seem crazy that someone would go to the doctor with a medical problem and then refuse to be treated. But the fact is that prescription drugs can be so expensive that many people don't fill the prescriptions their doctors give them.

A group of Canadian researchers looked at this issue of primary nonadherence, or failure to fill a first-time prescription, to see what can be done to improve disease management.

The cost of medications is definitely a deterrent, Robyn Tamblyn, corresponding author on the study told TheDoctor, and physicians often do not know how expensive a medication is.

Even when patients do ask their physicians for less expensive drug options, their doctors may not know the costs of the medications.

The researchers reviewed data from almost 16,000 primary care patients in Quebec, Canada. They found that 31.3 percent of first-time prescriptions were not filled.

Older persons, those in lower income groups without copayments, and those who had more visits with the prescribing physician were the groups more likely to fill their prescriptions.

Prescriptions for medications in the top 25 percent in terms of cost were the least likely to be filled. Prescriptions for gastrointestinal drugs, skin conditions, and chronic preventive therapies for conditions such as ischemic heart disease and depression were also less likely to be filled. Prescriptions for antibiotics, particularly for urinary tract infections, were the most likely to be filled.

Patients tend not to know that the cost of medications to treat a chronic condition, such as hypertension, can vary considerably, Tamblyn says. But in the case of hypertension, the less expensive medication is usually as effective as the more expensive medication. “So, the first question patients should ask is, ‘Is there a medication that is just as effective, but not as expensive?’”

For many chronic conditions, at least several possible treatments are available, and, she explains, the latest therapies are not necessarily the best. Generally, according to Tamblyn, four or five types of drugs could be used to treat a given condition.

The safety of newer medications is also often less clear, Tambyn says, so patients won't even know what sorts of complications could occur with them. The risks of older therapies that have proven to be effective over time are better understood and tend to be cheaper than newer ones.

Finally, even when patients do ask their physicians for less expensive drug options, their doctors may not know the costs of the medications. “It creates kind of a perfect storm to produce barriers to effective disease management that don’t necessarily need to be there,” Tambyn points out. She would like to see the list of therapies and their relative cost made more accessible to people receiving prescription treatments.

Giving patients this kind of information helps them have a say — or at least a better understanding — of how their conditions are managed.

The study was published online recently in the Annals of Internal Medicine.