Know Your GFR: CKD and Pharmaceutical Dispensing

If you have been diagnosed with chronic kidney disease (CKD), it is recommended that you are 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 medications that people with CKD should not use, or perhaps the drug dose must be significantly reduced. The following article will outline why informing your pharmacist of your kidney function may help ensure that your prescribed medications 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 medications.

Ideally, community pharmacists have access to your lab values. When I had access in my last province of employment, it provided a valuable tool to assess the safety of medications prescribed for an individual with chronic kidney disease. From my experience, some people with CKD are not aware of their glomerular filtration rate values, and 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 and, therefore, would not be able to determine whether certain medications are safe for you unless you inform the pharmacist of your lab test results.

How medications can impact the kidneys

Medications can have various effects on the kidneys: they can either be excreted by the kidneys or cause direct harm to the kidneys.¹

The kidneys excrete some drugs to eliminate them from the body. In people with poor kidney function, the drug could accumulate and potentially build up in their bodies and cause side effects. The pharmacist must know your glomerular filtration rate to make a dose reduction to your medication.

Some examples of medications include:¹

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

Medications 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 non-steroidal 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 medications 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 medication is safe for the prescribed individual.

My colleagues and I have witnessed multiple instances where a patient diagnosed with chronic kidney disease 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 re-ordered for the correct dose when this is identified.

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 medication is prescribed for you, it is safe for you.

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