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Furosemide (Lasix) Side Effects & Generic Troubles

Furosemide (Lasix) side effects are not always fully described. Be aware of side effects such as incontinence, dizziness, diabetes and kidney damage.
Furosemide (Lasix) Side Effects & Generic Troubles
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Furosemide is a diuretic that is one of the most prescribed drugs in the world. At last count over 7 million Americans swallow this water pill every day to lower their blood pressure or help their kidneys shed excess fluid. It is just behind another diuretic, hydrochlorothiazide (HCTZ), on the doctor’s hit parade of commonly prescribed medications. It is perceived as extremely safe, but furosemide (Lasix) side effects can be potentially serious if missed or ignored.

Furosemide is a “loop” diuretic, meaning that it affects a special part of the kidney called the loop of Henle to facilitate salt elimination from the body. This medication not only kicks sodium out of the body (considered a beneficial action), it also promotes removal of other key minerals such as magnesium, potassium and calcium (all undesired consequences). Many health professionals are aware of the potassium problem, but they may ignore the depletion of magnesium. Low levels of magnesium and potassium can have devastating consequences.

Furosemide (Lasix) Questions Received at People’s Pharmacy:

One woman worries about her husband’s incontinence with furosemide:

Q. “My husband’s doctor is concerned about his blood pressure. It has been fine until three days ago when at the doctor’s office it was 140/80. (When we got home it was 125/75). The doctor doubled his dose of furosemide.

I frankly am afraid he is going to end up in the hospital! I would like to learn more about this drug. My husband fortunately works close to home; he sometimes urinates on himself because he can’t always make it to the bathroom in time. He does operate heavy equipment at times and the dizziness thing is scary too. Please tell us more about furosemide (Lasix) side effects.”

A. Sadly, there is very little research on the effect of furosemide on bladder control. That said, there is a recognition that this diuretic may induce OAB (overactive bladder). In practical terms that means furosemide could lead to frequent urination, hard-to-control urinary urges and even an occasional bout of urinary incontinence (BMC Geriatrics, June 10, 2013). The increase in the dose of furosemide might also be contributing to his occasional accidents (Heart-Lung, Jan-Feb, 2013).

Dizziness is not uncommon with furosemide. We worry a lot about this side effect because it could cause a fall. You mention that your husband operates heavy machinery. Dizziness or vertigo could make this activity dangerous. Please discuss your concerns with the prescribing physician. There are many other options for treating high blood pressure. Some experts believe that furosemide should not be a first-line treatment for hypertension. A big dose of furosemide may not be the best option for your husband unless there are other health concerns you have not mentioned.

Can furosemide affect the kidneys?

Q. “As part of the medications I take for high blood pressure, I take Lasix two times per day, 40 mg each.

“I am concerned as I just read that Lasix can potentially cause kidney damage or gout when taken over a period of time. I am very concerned that I have never been told about these serious side effects from my doctor. Are they true?”

A. We are disappointed that health professionals do not always mention furosemide (Lasix) side effects. Kidney damage is one possible adverse reaction (European Heart Journal. Cardiovascular Pharmacotherapy, June 19, 2017). It is listed in the official prescribing information but has not been well recognized by clinicians. Many people just assume that it is bad luck, but furosemide, especially in higher doses, may be a contributor. Gout (brought on by elevated levels of uric acid) may also be triggered by furosemide (Arthritis & Rheumatology, Dec. 29, 2011).

How much potassium is necessary with furosemide?

Q. “I take prescribed 20 mg Lasix twice a day. One doctor says to take potassium with it, but another doctor says no. I don’t know what to do.”

A. Furosemide can deplete the body of both potassium and magnesium. Because it is impossible to predict how any given individual will react, the only way to know whether you need potassium and/or magnesium supplements would be to have your physician order a blood test for both minerals. We would encourage you to have this done periodically since levels can change over time. If you are indeed low in potassium your physician will be able to determine the most appropriate dose.

Can furosemide cause hearing loss?

“My wife (54 years old) started furosemide 20 mg twice a day for fluid retention. It has helped with that, but has caused hearing loss in both ears. She has been told to stop for two weeks and see her doctor for blood work afterwards.”

A. The official FDA-sanctioned prescribing information lists tinnitus (ringing in the ears) and hearing loss as possible side effects of furosemide.

Will furosemide raise blood sugar?

Q. I have a very good friend who suffers from serious heart problems. He had a pacemaker implanted many years ago. That was replaced with a defibrillator pacemaker. He has been taking many medications for his heart problems, including furosemide (Lasix). He was diagnosed with diabetes about three years ago.

A few months ago, he was taken to the ER when he became very short of breath. They ran many tests and one doctor switched him from Lasix to torsemide (Demadex). Ever since this change, his blood sugar has been completely normal. Is diabetes one of furosemide side effects?”

A. There is evidence that furosemide can affect the body’s ability to handle carbohydrates leading to elevated blood sugar levels (hyperglycemia). Over time this might increase the risk for diabetes.

Furosemide (Lasix) Side Effects:

As you can see from the questions above, this diuretic is associated with a number of unexpected complications. In seeking answers to these questions we were surprised at the lack of really high-quality research into the adverse effects of furosemide. For example, there is very little information about the negative impact of furosemide on kidney function. What we found was new and worrisome (European Heart Journal. Cardiovascular Pharmacotherapy, June 19, 2017).

Because it is a water pill (eliminates fluid from the body), it can cause numerous trips to the bathroom. As one reader reported above, it led to incontinence for her husband at work. Others complain that they have to get up numerous times a night to pee.

More serious is dizziness. The same wife who worried that her husband had “accidents” at work also mentioned that he handled heavy equipment and experienced dizziness. We worry that dizziness can make anyone susceptible to falls.

We also worry about depletion of potassium and magnesium. These electrolytes are essential for muscle function. When they are depleted from the body, muscle cramps are not an uncommon complication. Irregular heart rhythms can also occur and this can be a life-threatening situation if not corrected.

Anyone on furosemide must have regular blood tests to make sure electrolytes don’t get out of whack. In some cases potassium and magnesium supplements are necessary, but they require medical supervision and close monitoring to make sure the levels are like Goldilocks and the porridge (not too hot or too cold…too much or too little).

Other concerns mentioned above include hearing loss, gout and diabetes. These furosemide (Lasix) side effects should not be discounted. Diuretics not infrequently raise blood sugar or trigger diabetes. By now most people realize that this can have devastating results including an increased risk for heart disease, dementia, strokes and blindness. Gout can be incredibly painful. It can be brought on by excess uric acid levels in the body, a direct result of diuretics like furosemide or hydrochlorothiazide.

Other Furosemide (Lasix) Side Effects to be Alert For:

  • Weakness, muscle cramps (linked to electrolyte depletion)
  • Dehydration, weakness
  • Irregular heart rhythms (contact an MD immediately!)
  • Dizziness, low blood pressure, especially when standing suddenly, vertigo
  • Ringing in ears, hearing loss (contact an MD immediately)
  • Blood problems (contact a physician if bruising or anemia occurs)
  • Blurred vision
  • Skin rash, itching (potentially life threatening, contact an MD immediately!)
  • Elevated uric acid levels, gout
  • Elevated blood sugar, diabetes
  • Increases in cholesterol levels and triglycerides
  • Kidney damage

No one should ever stop furosemide suddenly without medical supervision. This drug is essential for certain heart patients, especially those with congestive heart failure. Keeping excess fluid under control is critical for such patients. But furosemide is a tricky drug and requires very close monitoring by an attentive health care provider.

Furosemide can also interact dangerously with dozens of other medications, so the pharmacist must check any other medicine that is taken to make sure there are no incompatibilities. Always ask your doctor and pharmacist to check for drug interactions with furosemide. Here is why it is so important:

“My husband took furosemide for many years. We now know from the cardiologist who is caring for my husband that he was taking too many drugs that were not beneficial for him including furosemide. He was like a zombie–just wanted to sit and do nothing.

“After this cardiologist took my husband off this drug, plus others, plus prescribing something else instead and reducing the amounts of other drugs, my husband miraculously became alive again. He is now 86 years old and has survived two life-threatening surgeries. He is now very active and building things like he used to that he loved to do. He does many tasks and does not want to sleep all day, eats well and does so many other things.

“I am hoping people who take this drug and many others that you have written about will take heed and ask their doctors to check their drugs out very carefully. When my husband had surgery, he wasn’t recovering well. I found out that he was taking drugs that he shouldn’t have been. His cardiologist immediately started checking out what I had found and was amazed that all those other Drs. were not checking his meds, dosage, etc.

“Once again Dr. Graedon and Mr. Graedon, thanks for such a wonderful column and all the information you write about alerting and showing us so many natural remedies to use instead of harmful drugs.” Sincerely, Mrs W.

Lasix vs. Generic Drug Substitution:

We have received a number of complaints that not all generic furosemide is created equal. We are especially worried about this problem for people with heart failure. If their medicine is not working as anticipated, it can lead to fluid accumulation and life-theatening complications.

We fear that the FDA has not been as vigilant about monitoring generic drugs as most health professionals think. Here are just a few stories for your consideration. If you suspect that your generic furosemide is not working as intended, let your physician and pharmacist know that this is a problem other people have encountered.

“I have mild congestive heart failure and real bad edema, with my left leg especially. I take 80 mg Lasix twice a day. The brand name works quite well. Some of the generic furosemide seems to work but it seems to have a wide range of effectiveness from manufacturer to manufacturer.

“The generic furosemide that my mail order pharmacy sends me seems to do little or nothing. I may as well be taking chalk tablets. On this stuff I retained so much water that I would gain about 15-20 lbs or more and have shortness of breath. My legs would swell up badly. I have to keep a Lasix prescription at the local pharmacy and pay for it out of my own pocket to avoid problems.”

“I take furosemide, 20 mg tablets, and for a long time took Mylan brand generic. Then the pharmacy switched me to brand XXX generic. I immediately began ‘drowning,’ and my weight jumped 5 lbs overnight. I fortunately had some Mylan brand still on hand, switched back, lost the water, and three days later tried the brand XXX again. Same result. I am on an assigned Medicare Part D Plan, and as a result the Mylan has to be special-ordered and approved for me to get it.

“These are both generic forms of the same drug, but even among generics there are big differences. A major concern is that while I recognized the problem and took immediate action (and then tested the problem out again), there are a lot of elderly people on furosemide, for instance, who would not understand this type of problem with the pill. They could end up seriously ill, with their doctors blaming them for ‘non-compliance’ problems: “Mrs. D is not taking her furosemide as directed,” when in fact it was the drug manufacturer at fault.”

“Before I retired as a pharmacist, the two generic drugs that I received the most complaints about were generic Lasix and generic Ritalin.” Mark

Share your own story about furosemide below. Has it worked well for you? Have you experienced any furosemide (Lasix) side effects? Have you had any problems with generic formulations? Others may benefit from your comments. If you are taking furosemide for hypertension, you may find our Guide to Blood Pressure treatment of some value. It offers a number of non-drug options to discuss with your physician.

Revised: 6/22/17

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies. .
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