Know Your GFR: CKD and Prescription Drug Dispensing

Editor’s Note: This article was written by Nour Sahib and originally appeared on our partner site Type2Diabetes.com.

If you have been diagnosed with chronic kidney disease (CKD), you should be aware of your glomerular filtration rate (GFR) and serum creatinine values. These values are kidney function markers. While the exact value is not important, it is crucial to know the general values when you are receiving care outside your regular health team.¹

There are several medicines that people with CKD should either not use or may need to reduce the dose of. The following article outlines why informing your pharmacist of your kidney function may help ensure that your prescribed drugs are safe for your kidneys.

Inform your pharmacy of your lab results

I am a pharmacist and have practiced in various provinces within Canada. The current province I practice in does not provide me the option, at this time, to view patients' lab values when I dispense medicines.

Ideally, community pharmacists have access to your lab values. When I had access to this information in my last province, it was a valuable tool to assess the safety of medicines prescribed for people with CKD. From my experience, some people with CKD are not aware of their GFR values. Therefore, having access to that data is helpful as a pharmacist.

This may be the case for where you live as well. Pharmacies may not have access to your lab values. Therefore, they may not be able to determine whether certain medicines are safe for you unless you inform the pharmacist of your lab test results.

How medicines can impact the kidneys

Drugs can have various effects on the kidneys. They can either be filtered out by the kidneys or cause direct harm to the kidneys.¹

The kidneys filter out some drugs to eliminate them from the body. In people with poor kidney function, these drugs could build up in their bodies and cause side effects. The pharmacist must know your GFR to reduce the dose of a medicine you are taking.¹

Some examples of these drugs include:¹

• Allopurinol (gout medicine)
• Acyclovir (antiviral)
• Various antibiotics (nitrofurantoin, ciprofloxacin)

Medicines that directly harm your kidneys

These drugs are referred to as nephrotoxic agents and can directly worsen your kidney function. Examples include aminoglycoside antibiotics and nonsteroidal anti-inflammatory drugs (NSAIDs) such as Advil or Celebrex.¹

Shouldn't it be the doctor's role?

You may be thinking, Shouldn't it be the doctor's responsibility to determine whether medicines and dosages are appropriate for their patient? Most doctors do a good job of this, but mistakes happen. The pharmacist acts as a final check to ensure that the prescribed drug is safe for the individual.

My colleagues and I have witnessed multiple instances where a patient diagnosed with CKD was prescribed an antibiotic, for example, at a dose double what they should be taking. The pharmacist can then contact the doctor and get the drug reordered for the correct dose when this happens.

Keep a record of your GFR results

If your pharmacist does not have access to your lab results, keep an ongoing record of your GFR readings. Carry this information around to help your pharmacist ensure that when a new drug is prescribed for you, it is safe for you.

Do you have a story about a time when a medicine had to be adjusted/stopped due to your kidney function? Share your experiences below!