Monitoring Loop Diuretics; What Do I Think About?

Loop diuretics are the mainstay in removing fluid off the body in patients with heart failure. They are very common in clinical practice. What should you think about when monitoring loop diuretics?

Monitoring Loop Diuretics – Benefit?

One of the challenges with polypharmacy in our geriatric patient population is to continually assess the benefit of the medication. Loop diuretics are no different. Monitoring weights and symptoms of heart failure and edema are important to ensure that the medication is still necessary and beneficial. For many patients, furosemide will be necessary long term, but ensuring we are at the minimum effective dose can help us minimize the risk of complications.

Prescribing Cascade

As a pharmacist who focuses heavily on geriatrics, I can’t tell you the number of times I’ve seen medication adverse effects lead to new prescriptions for diuretics and/or escalating doses. NSAIDs are probably the most common drug class that can contribute to edema and they are easily accessible to patients. It is critical to review the medication list and ensure that medication adverse effects aren’t causing the use of a loop diuretic. Here’s a list of my top 5 drugs that exacerbate heart failure and cause edema.


Adverse effect monitoring with loop diuretics is critical. I always start with electrolytes. Significantly low electrolytes like potassium can lead to the risk of arrhythmias and other complications. We have to make sure that this is assessed and in most situations, supplementation may be necessary.

Renal Function

By removing fluid from the body, we can increase the risk of dehydration. Dehydration can cause acute renal failure. When you check electrolytes, you need to also monitor kidney function. I discuss drug interactions that can exacerbate the risk of renal impairment on this episode of the Real Life Pharmacology podcast.

Urinary frequency

Urinary frequency can be very troublesome to patients and I have had many patients that will stop taking their furosemide due to this adverse effect. The most common situation I have encountered is when a patient knows they are going to be more active in social settings, or have other situations where they do not want to be going to the bathroom a lot, they may elect to skip doses of their furosemide.

There is an inherent risk of fluid accumulation and exacerbation of heart failure if too many doses are skipped. It is important to discuss this with patients and try to get a sense of how many doses they are skipping because of this potential adverse effect.

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1 Comment

  1. Alex Chan

    There is also the threshold effect of furosemide that governs its dosage. In order to reach the effective dose it needs to hit the threshold. A stepwise approach would be to start dose at 20-40mg then double dose until adequate urine output is achieved. If adequate urine output occurs with a dose but patient is still fluid overloaded then the dosing interval interval to twice daily.


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Written By Eric Christianson

May 10, 2020

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