Lasix is a water pill used in heart failure patients and as a treatment for high blood-pressure. Many people are prescribed Lasix. In fact, I'm willing to bet you a penny that you know at least one person who is on it. Unfortunately, many people are incorrectly using Lasix.

When I was in medical school at the University of Connecticut, one of my favorite rotations was my surgery experience. At night, on call, and waiting for admissions, I sometimes watched television with the residents — usually if we were not in the mood to study. The television show "ER" was very popular at that time. I remember a question asked on the show: "Is Lasix (furosemide) a once a day medication?" The answer is no. Lasix is a twice a day medication.

Fast forward to today. I'm currently studying for my Kidney recertification exam. One of the study questions asks how to dose Lasix. Surprisingly, most physicians get this one wrong. Most providers prescribe Lasix once a day.

I frequently get consulted for resistant high blood-pressure. The patients I see tend to be on multiple blood pressure medications. One of the first things I do is recommend to my patients that they take their Lasix twice a day. Why is this recommendation necessary? The kidneys are extremely smart organs. When a water pill is given that only lasts for 6 to 12 hours, the kidneys will spend the remaining 12 hours of the day recovering the lost fluid resulting in net zero fluid loss.

The secret to tolerating Lasix is to know what to expect. Be prepared to urinate a lot both during the day and night when you first start Lasix twice daily, or when the dose is increased. After about 4-5 days of using this diuretic, your body will adjust, and you will be less likely to wake up at night to urinate.

So remember, Lasix (furosemide) lasts 6-12 hours and needs to be taken TWICE DAILY in order to work correctly. Ask your doctor if you have any questions regarding Lasix (furosemide).

Another week, another question from an email subscriber: I had eclampsia in July 2008, I would have loved a kidney consult! Can there be any long term consequences of protein in the urine in pregnancy?

Dr. Aaronson: Thank you so much for your question! I appreciate the fact that you value my opinion.

Pre-eclampsia refers to high blood pressure and protein spillage in the urine after 20 weeks of pregnancy in a woman who had a normal blood pressure prior to getting pregnant. When the preeclampsia gets bad enough, a person may have a seizure. When this occurs the woman is said to have eclampsia. Normally, delivery of the baby is the treatment of choice to protect both the mother and the infant.

Mothers are at risk for recurrence of pre-eclampsia/eclampsia during their next pregnancy. Those who were diagnosed early on in the pregnancy and were noted to have been in critical condition have a 25-65% risk of reoccurrence. OB-Gyn doctors will watch you very closely and try to help prevent a recurrence.

Unfortunately, women diagnosed with preeclampsia are at greater risk than their counterparts for heart disease and stroke and should be treated aggressively by their provider for any risks they might have. Also, these women have an increased risk of kidney disease, including the need for dialysis. You may want to find out how much protein you currently are spilling in your urine. That helps the doctor make decisions regarding your care.

My recommendation: make sure you see your doctor and focus on preventive care and goal rate attainment. If you note that you have a GFR of 60 or less, have residual protein in your urine, or have any concern regarding your kidney function, please feel free to make an appointment with a kidney specialist.

A question from one of our email subscribers: "I have a friend with childhood onset sugar diabetes. She is 40 years old. She takes great care of herself. She recently got an insulin pump and her sugars have been great. She exercises every day. After seeing her primary care provider, she was told her GFR (her level of kidney function) was down to 50 (normal is 100) — this was 2 weeks ago. Six months prior it was 56. They said they'd recheck it in 3 months. Well, this week she got short of breath and was concerned that she was having a heart attack. She had a stress test today that went well. They rechecked her GFR though and it was 43. Her primary doctor told her if it goes below 40 she's going to have her see a nephrologist / kidney specialist. A kidney U/S showed that her kidneys were slightly smaller than normal but had good blood flow. They are rechecking her kidney function in one week. Any thoughts? I wonder if the worsened kidney function is a fluke or something we should be concerned about? Thanks!"

Dr. Aaronson: Thank you for asking this question. Understanding kidney function can be complex. Let me simplify. Even though we normally have about 2 million kidney filters, kidney doctors say that a person with no kidney problems has 100 filters. These 100 filters perform the job of removing toxins and fluid from the body every day. In doctor-speak, this person has a "GFR" or filter rate of 100 per cent function.

Over time, people with diabetes and high blood pressure can damage some of the filters. The woman in our case study has 50 out of 100 filters to do the job (50 per cent function). These filters have a lot of work to do, but they can get it done and a person doesn't have to get kidney dialysis. As more and more filters get damaged, the remaining ones start to get overworked. Eventually when there are 10 to 15 filters left, the filters are unable to remove the toxins and fluid from the body, and the patient requires an external filter (a kidney dialysis) to get the job done.

Primary care physicians have different cutoffs in terms of GFR the patient has to have before they are willing to consult a kidney specialist. Of course, I am happy to see the patient at any level of kidney dysfunction for any reason. However, I would much rather have 60 filters to work with than 40. When there are only 20 to 30 filters left, my job gets harder and the chances of preventing kidney dialysis is even worse. Many nephrologists or kidney doctors would recommend consultation when the kidney function, the GFR drops below 60. This is the magic number.

A lot of things change in the body when the GFR is around 60 or below. People can become anemic, tired and fatigued. People can have major bone problems. People can have potassium and other electrolyte problems. Kidney specialists can help the primary care physician with these kidney specific issues. What's more, targets for blood pressure and cholesterol are lowered. So control becomes harder to obtain. Kidney consultants can help the primary care doctor and the patient achieve these new goal targets.

In this case, I do agree with checking a blood test in one week. However, whether or not the lower number was a fluke doesn't change the fact that this woman needs to see a kidney doctor. In addition to what was just mentioned, I would like to know if the patient has any protein or blood in her urine. If she has protein, she would be a candidate for a medications such as benazepril to help prolong the life of her kidneys — even if her blood pressure is normal! Iron studies to evaluate for iron deficiency anemia would also be indicated. Target blood pressure should be 130/80, and I would argue that the patient should have an LDL (bad) cholesterol of 70 or below, triglyceride level of 150 or below, and HDL (good cholesterol) of 40 or above. If there is any evidence of secondary hyperparathyroidism, the person needs to be treated.

Make sure your physician tells you your GFR. Terms like "creatinine" have less meaning and is not enough information, because your creatinine level is only a rough estimate of your kidney function.

Now you know if the number is below 60 you should see me. If the number is trending down quickly, even if it is above 60, you should see me. If you are concerned, you should see me. My goal at that time would be to prevent further worsening of kidney function so that you never see the kidney dialysis machine. However, it is important to note that if you do need kidney dialysis, I can help you with that.

Kidney doctors are frequently asked to give their opinion on whether a patient should continue taking a nonsteroidal medication (Advil, Motrin) or switch to an alternative such as Tylenol or a scheduled narcotic.

Chronic pain is very common. After over-the-counter medication has been tried and has failed, patients come to their family doctor for help.

 There are two broad categories of non-narcotic pain medication:

1) Nonsteroidal anti-inflammatory medication: Motrin, Advil, and many others. This class of medication treats pain, fever, and inflammation (swelling). Ibuprofen is a type of non-steroidal that is processed in the liver.

2) Tylenol: this medication treats pain and fever but NOT inflammation. Tylenol is excreted in the urine but in some circumstances affects the liver.

Patients who have arthritis are usually prescribed nonsteroidal anti-inflammatory medication. NSAIDS are very powerful pain control medicines and frequently do the trick. Not only do they control pain, but they also to help decrease swelling in people's joints.

"So, if ibuprofen is processed in the liver and Tylenol is excreted in the urine, why is Tylenol "safer" for the kidneys than ibuprofen?"

Patients with chronic kidney disease can be very sensitive to non-steroidals. Their kidney function can get worse, and their blood pressure can go up. So even though a medicine such as ibuprofen is processed in the liver and is meant to control pain, it can have untoward effects on the rest of the system -- in this case the kidneys and the blood pressure through complex mechanisms. When this happens Tylenol is usually recommended because it doesn't adversely affect the kidneys. The big downside here is that Tylenol doesn't help decrease the swelling of inflammation.

It is important to note that the kidney doctor doesn't write for the pain medicine. The kidney doctor performs a risk/benefit analysis with the patient so that the patient can make informed decisions regarding what to do. Some people are willing to risk worsening kidney function and hypertension in order to have their pain and inflammation treated. In that case the nephrologist will try to help prevent worsening kidney function and high blood pressure at all costs. On the other hand, some people may want to avoid blood pressure and kidney problems and choose Tylenol (and possibly a narcotic with the help of a pain specialist). When I was training, we were taught to avoid nonsteroidal medication at all costs when the blood pressure or the kidneys were affected. However, my problem with this is that a life of severe pain may be so intolerable that the risk of kidney decline may be something to consider if a patient can get some relief.