The Importance of Good Kidney Function: A Concise Overview of Important Information for Avoiding Adverse Drug Reactions
The Importance of Good Kidney Function: A Concise Overview of Important Information for Avoiding Adverse Drug Reactions
There are many things to be concerned about when you or a loved one are taking medications, whether they are prescription or OTC. Your pharmacist might not be informing you all of these things.
To give just one example, it's common knowledge that taking multiple medications at once can lead to dangerous interactions. The fact that medication allergies can be rather dangerous is also well known. This is covered in previous entries in the series. Additionally, it is well-known that certain populations may be more vulnerable to adverse medication events, including very young children, the elderly, pregnant women, nursing mothers, and those with severe disabilities.
The results of a simple blood test can be crucial in determining the correct dosage of many medications, but unfortunately, your pharmacist will rarely have access to this information, particularly if they fill your prescription at a retail drugstore. This is something that most people are unaware of. (Ah, what a disappointment.)
Naturally, the "serum creatinine test" (pronounced "SEAR-em cree-AT-tuh-neen tehst") is the one I'm referring to. No one has to be in the dark about this test—which is both challenging to pronounce and understand—if they or someone they care about is taking any kind of drug, whether it's over-the-counter or prescription.
The serum creatinine level provides a rough indication of renal function to the doctor or pharmacist.
The "bean counter" of contemporary medicine, serum creatinine indicates whether the kidneys are functioning optimally.
Just how crucial is that?
Well, renal function is crucial for calculating the right dosages of many drugs because the kidneys (and the liver) help excrete meds from the body.
The kidneys, the liver, or a combination of the two organs is responsible for eliminating the majority of drugs and their chemical by-products.
There will be a rise in the danger of drug side effects due to the accumulation of several medications in the body when the beans are not operating correctly. And that's much more disappointing. (We will get into the topic of liver disorders in a later essay in this series, but the general idea is the same.)
Consequently, many drugs require lower doses in people with impaired kidney function.
Then how exactly does it function?
In any case, creatinine is a naturally occurring and circulated molecule in humans. It is a natural byproduct of protein cleavage. And beans, like many drugs, typically pull creatinine out of the blood. Thus, similar to the effects of many drugs, an increase in the blood level of creatinine indicates that the kidneys are not functioning properly.
The serum creatinine test is a common and easy way for doctors and pharmacists to measure blood creatinine levels. Including this test in a battery of blood tests is not uncommon. Additionally, several medications require a dosage reduction when serum creatinine levels are high. While lab values could differ somewhat, a normal range for serum creatinine is between 0.4 and 1.5 mg/dl.
When your kidneys aren't working, your serum creatinine levels will rise.
Although there are more precise ways to gauge kidney function, serum creatinine is often the go-to for estimations because it is easy to obtain, doesn't cost much, and provides results that are sufficient for most applications.
"Creatine clearance" (cree-AT-tuh-neeeen CLEAR-uhhh-nce) is the medical community's go-to metric for gauging kidney function. But because it is so stinky and bothersome, not many patients receive this test. You need to record your pee output for a whole day and store it in the fridge. Very few people have volunteered to take this test...
Typically expressed in milliliters per minute, creatinine clearance measures the amount of blood that the kidneys eliminate from the body in a specific time period.
Creatinine clearance, or the quantity of blood that the kidneys are effectively "cleaning," falls as a result of impaired kidney function.
If your kidneys aren't working, your creatinine clearance will go down. Keep in mind that this goes against your initial assumptions and the way serum creatinine works, so it's easy to remember. Like this, the majority of medication is.
For those who are determined to get an A, here is the extremely challenging portion. Wow, it's quite cool that serum creatinine can be used to "guesstimate" creatinine clearance. In the absence of a measured creatinine clearance, that is likely the most accurate method for assessing renal function.
An estimated creatinine clearance, a measure of renal function, is obtained by running the serum creatinine measurement through a complex equation. (I thrive in rigorous scientific pursuits, such as estimating the estimates of estimates.)
That equation is the hated but renowned "Cockcroft-Gault equation adjusted for ideal body weight and gender" for adults. Due to its lack of rigorous validation in a wide range of patient populations, including those with varying body mass indexes, the Cockcroft-Gault equation—so named after the medical professionals who developed it—is widely believed to be very accurate. See for yourself. If you can commit this to memory, you'll get bonus points:
Creatinine clearance values for males are
/ (72'SCr) * ((140 - Age)' IBW)
A woman's creatinine clearance is equal to
((140-Age)' IBW' 0.85 / (72' SCra)
The variables here are age (in years), optimum body weight (in kilograms), and serum creatinine (in milligrams per deciliter; SCr).
Visit this creatinine clearance calculator if you're having trouble with algebra or just want some help figuring out the answers to these tricky questions: Visit this website: http://www.medicationadvisor.com/creatinine/creatinine.asp.
It turns out that young, healthy persons have a creatinine clearance of around 100 ml/min (for the rest of this, we'll just ignore the'ml/min' bit).
Additionally, the creatinine clearance of a healthy person when they die is approximately zero.
The rest of us are haphazard.
"I just ran this on myself and I have a creatinine clearance of 150," someone says from behind the scenes. So, what makes you unique? Even if a creatinine clearance of 100 is considered normal, it is not helpful for young, attractive persons to have 130, 140, or even higher. Overachiever excess is the real culprit here.
A creatinine clearance of 80 indicates that the kidneys are functioning at an 80% level.
By the way, 50% renal function is indicated by a creatinine clearance of 50%. (Do you understand all I'm saying?)
Once a patient's renal function falls into the 40-60 range, they will need to moderately reduce the dosage of several medications that are removed by the kidney.
Patients in the 20–40 age group usually necessitate substantial dosage decreases.
Additionally, individuals with a creatinine clearance of less than 20 mg/dL will typically require extremely low doses of drugs metabolized by the kidneys (or, even better, they should seek for alternatives to these drugs that are metabolized by other organs).
A final nugget to think about. Reduced kidney function is a common symptom of aging. That is an undeniable fact. However, everyone's rate of decrease is unique. You should expect to have intermediate renal function (or worse) by the time you're 50 years old. By the time you're 80 years old, you'll almost surely have some significant degree of renal impairment... and you might not even be aware of it or feel it.
We can return to the article's central topic—medication safety—now that you have learned more about renal physiology than you ever wanted to know.
Do what you need to do to take charge of this situation if you or someone you care about is at risk for impaired kidney function (I'll reveal who these people are in a second). Your doctor and pharmacist probably didn't have information about your renal function or didn't take it into account when they prescribed you medication.
My advice to anyone using any kind of medication, whether it's over-the-counter or prescribed:
1) Everyone should commit the results of a recent serum creatinine test to memory or write them down. When prescribed medication, individuals should inform their doctor or pharmacist, "I believe my serum creatinine is about X." This information is typically included in annual physicals, so it's easy to find. Would it be necessary to change the dosage of this medication for me to be safe?
The following groups should anticipate that their doctors and pharmacists would take renal function into account when prescribing medication:diagnosed renal disease;over the age of 50;a background of cardiovascular disease, chronic pain, stroke, or other vascular occlusions;medical history involving diabetes;previous hypertension;previous experience with chemotherapeutic medications;background of extended intravenous antibiotic use;regularly using painkillers (particularly NSAIDs, although not limited to them).
Because your health condition X may impair your kidney function, you may wish to inquire with your doctor or pharmacist, "Is this drug removed by the kidney?" Ask your doctor or pharmacist to tell you your serum creatinine level if the drug is excreted via the kidneys; if they don't know, it should raise red flags.
3) It's okay if you don't have a serum creatinine on hand and you don't fit into any of the groups mentioned in question 2. I'd say you're probably okay. On the other hand, you should inquire with your doctor about the presence and type of serum creatinine in your medical record.
4) Serum creatinine is usually not a good indicator of how much medication to give someone who is on dialysis. You should just inform your doctor and pharmacist that you are undergoing dialysis, and you might want to inquire, "Now is this the usual dose for someone on dialysis?"
To ensure that you or a loved one are receiving the correct dosage of any medication, whether it is prescribed or purchased over-the-counter, I hope that you will take these measures into consideration the next time you need to do so.
No way!
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