Flomax for Kidney Stones

Medical knowledge is always evolving. New treatments are often released to improve the symptoms of patients while reducing the incidence of side effects.  

Similarly, recent advancements in the medical sciences have uncovered the role of Flomax to treat kidney stones, a medication originally designed for patients with benign prostatic hyperplasia (BPH). 

However, what is Flomax, and how does Flomax work in cases of kidney stones? Is it an effective and safe treatment? Does it replace surgery and other therapeutic options?

What is Flomax? 

Flomax is the trade name of tamsulosin, a medication that treats benign prostatic hyperplasia.

It is an alpha-blocker, which means it interferes with the nervous transmission of a  group of neurons by blocking a series of receptors.

The main effect in benign prostatic hyperplasia is relaxing the muscles of the prostate. It is useful to relieve the urinary symptoms that result from an enlargement of the prostate gland.

After its release in 1997, tamsulosin started to be prescribed.  Not only to improve the symptoms of BPH but also for other urinary problems.  These include acute urinary retention and to pass kidney stones faster and with reduced severity of symptoms (1). 

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What are kidney stones? 

Kidney stones are one of the most common causes of visits to the emergency department worldwide.

It is estimated that most people will experience symptoms of kidney stones at some stage in their lives. They form from calcium oxalate crystals or uric acid crystals.

Kidney stones grow as a buildup of various compounds that become sedimented in the upper urinary tract. The majority of them are not noticed because they do not grow big enough and can be eliminated without any significant symptoms. 

Larger kidney stones cause severe pain and other symptoms that often lead patients into an emergency room.

The majority of cases are solved by urinary elimination, dissolving kidney stones, and treating pain. However, in some cases, kidney stones are very large and should be surgically removed.

There are a wide variety of medications and dietary recommendations to treat patients with kidney stones.  Various preventative measures to reduce the incidence of recurrence in these patients.

However, the best treatment option usually depends on the chemical composition of the kidney stones. It is also dependent on the size, location, and whether or not it has triggered an infection of the urinary tract (2). 

Symptoms of kidney stones 

Many patients with small kidney stones do not display any symptoms throughout their lifetime.

In these cases, kidney stones are very small, and they eliminate without symptoms when patients urinate. However, when symptoms start to appear, they usually include pain, blood in the urine, and nausea with or without vomiting. 

Pain triggered by kidney stones is often located on the affected side of the spine, below the ribcage, which is why it is described as flank pain.

The nature of the pain is variable, and it often irradiates to the groin, testicles, labia majora, or the legs. It is a very intense pain, and it is often accompanied by profuse sweating, nausea, and vomiting. 

Not every case of kidney stones includes blood in the urine as a symptom. However, it is an important sign that the stone is passing through the urinary tract.

Other symptoms include a burning sensation while urinating and fever, especially when there’s a urinary tract infection associated with an injury to the inner linings of the urinary tract (3). 

How does Flomax work for kidney stones? 

Flomax is an alpha-blocker, and in the urinary tract, there are various forms of alpha-adrenergic receptors. These receptors link to smooth muscle. When they become activated would trigger muscle contraction.

This leads to a relaxation of the smooth muscle, that limits not only to the prostatic urethra but the rest of the urinary tract as well. This effect is more pronounced in the distal portion of the ureters and the bladder neck, areas with a higher concentration of alpha 1D receptors (4). 

When kidney stones are working their way through the ureters, the smooth muscle typically contracts. This can lead to a risk of entrapment of the stone and limiting its progression through the urinary tract (5).

In these cases, Flomax mediates relaxation of smooth muscles in the ureters. This, in turn, improves the flow of urine and solves the obstruction triggered by kidney stones and aggravated by smooth muscle contraction.

This effect by tamsulosin would also reduce the consequences of mechanical obstruction in the urinary tract. Such as hydronephrosis (swelling of the kidney that results from a backward flow and accumulation of urine). And complete urinary obstruction (an emergency situation attended by the urologist) (6). 

Is Flomax an effective treatment for kidney stones? 

Flomax (tamsulosin) is efficient in various studies. It can significantly reduce the time of the expulsion of these stones from the urinary tract.

Flomax for kidney stones

For instance, one study reports a 72% frequency of kidney stone expulsion in patients using Flomax against 30% in patients receiving placebo medications (7). 

Studies have also revealed that Flomax is an effective treatment to eliminate kidney stones smaller than 10 millimeters (9).

Studies show Tamsulosin can reduce elimination time in cases of kidney stones significantly. For example, one clinical trial reported that the elimination of kidney stones in a study took a mean of 7 days for the study group. This is in comparison to 9 days in patients who took placebo medications (7).

Moreover, in a subgroup of patients who had kidney stones smaller than 10 millimeters and located in the distal portion of the ureters, tamsulosin promotes expulsion of calculi in 4 days. This is in comparison to other traditional medications to manage kidney stones, which took a mean of 7 days (9).

Flomax is more useful for kidney stones located in the distal portions of the ureters. But, although lower, there’s still a significant reduction in elimination time for stones located in proximal areas of the urinary tract as well (10). 

The role of Flomax to treat kidney stones also includes emergency settings. 

What The Research Says

According to various clinical trials performed over the years, elimination is more efficient with Flomax for ureteral calculi located in the distal portion of the ureters.  This is the area where there is a higher concentration of alpha-adrenergic receptors (8).

Studies have evaluated the use of tamsulosin in patients with acute renal colic.

The results show that patients receiving tamsulosin in the emergency room have a lower requirement of pain medication and anesthetics. They also have a significant reduction in their hospital stay and lower the need for surgical removal (11).

These results of applying Flomax in the treatment of kidney stones may even lead to an estimated reduction of 29% in frequency of visits to the emergency department and a 24% reduction in healthcare expenses (12). 

The 2016 American Urological Association guidelines for the management of stones indicates that alpha-blockers may be beneficial for stones that are less than 10mm.  However, research is not conclusive on the use of tamsulosin in the treatment of kidney stones.

Recent research in the Journal of the American Medical Association concludes that tamsulosin was not effective in increasing the passage time for stones less than 9mm when compared with placebo.

Side effects of Flomax 

Tamsulosin belongs to a family of drugs with a specific affinity for alpha-adrenergic receptors. More specifically, the alpha 1 A and D sub-class. 

The known side effects reported so far dizziness and headaches. For the treatment of benign prostatic hyperplasia, further reported side effects include decreased ejaculation, blurred vision, and priapism.

Further treatment options for kidney stones 

There are plenty of therapeutic strategies for kidney stones. And there are both pharmacological and surgical options to choose from. However, this depends on the size and location of the calculi (3). 

Thiazide diuretics: They are commonly prescribed to encourage the urinary flow and reduction of urinary calcium that may reduce the recurrence of kidney stones in individual patients (2). 

Potassium citrate: Should encourage in calcium stone-forming patients to reduce the risk of kidney stone recurrence. It also increases the urinary pH and reduces the formation of uric acid stones. Potassium supplementation may also be required when thiazide diuretics are prescribed (2). 

Allopurinol: A drug employed to reduce the production and accumulation of uric acid. Doctors may prescribe it to patients with kidney stones, normal urinary calcium, and high levels of uric acid in the urine (2). 

Dietary modifications: Patients are often encouraged to increase liquid intake throughout the day, reduce sodium consumption and non-dairy animal protein, aiming at 1,000 to 1,200 mg of dietary calcium per day. Reducing the use of oxalate-rich foods is more important than reducing the consumption of calcium sources (2). 

Surgical measures: There are various minimally invasive and invasive procedures to clear kidney stones. These include extracorporeal shock wave lithotripsy, ureteroscopy, and percutaneous nephrolithotomy. Some of them require a postoperative ureteral stent, and the majority are outpatient procedures (3). 


Flomax is now becoming an essential part of the treatment in cases of kidney stones. However, despite being commonly prescribed, it can have severe side effects that patients should know. 

Flomax has the potential to interfere with a large number of medications to include warfarin and vasodilators. Therefore, it is imperative to speak with your doctor about any current medications you may be taking.

We know Flomax can induce relaxation of the smooth muscle in the urinary tract. It may also reduce the effect of entrapment that often leads to urinary obstruction in cases of kidney stones.

Guidelines for the management of stones indicate that alpha-blockers may be beneficial for stones that are less than 10mm.  However, some research concludes that tamsulosin was not effective in increasing the passage time for stones less than 9mm in comparison to placebo.

Before taking Flomax, discuss both the benefits and the drawbacks of this medication with your doctor. Depending on the size of your kidney stones, it can be an effective treatment.  But for smaller stones, dietary changes and reduce sodium intake may speed up the passing of kidney stones.

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  2. Pearle, M, Goldfarb, D, Assimos , D, Curhan , G, Denu-Ciocca, C. (2014). Journal of Urology. Medical Management of Kidney Stones: AUA Guideline. 192 (2), p316-324.
  3. Xu, H, Zisman, A, Coe, F, Worcester, E. (2013). Kidney stones: an update on current pharmacological management and future directions. Expert Opinion on Pharmacotherapy . 14 (4), p435-447 .
  4. DAVENPORT, K, TIMONEY, A, KEELEY, F. (2006). A comparative in vitro study to determine the beneficial effect of calcium-channel and a1-adrenoceptor antagonism on human ureteric activity. BJU INTERNATIONAL. 98 (1), p651–655.
  5. PORTIS, A, SUNDARAM, C . (2001). Diagnosis and Initial Management of Kidney Stones. AMERICAN FAMILY PHYSICIAN. 63 (7), p1329-1337.
  6. Peters, H, Eckstein, W. (1975). Possible pharmacological means of treating renal colic. Urological Research. 3 (2), p55–59.
  7. Gen Zhou, S, Lin Lu, J, Hong Hui, J. (2011). Comparing efficacy of α1D-receptor antagonist naftopidil and α1A/D-receptor antagonist tamsulosin in the management of distal ureteral stones. World Journal of Urology. 29 (6), p767–771.
  8. Lipkin M, Shah O. The use of alpha-blockers for the treatment of nephrolithiasis. Rev Urol. 2006;8 Suppl 4(Suppl 4):S35–S42.
  9. Aldemir, M, Emre Üçgül, Y, Kayıgil, O. (2011). Evaluation of the efficiency of tamsulosin and Rowatinex in patients with distal ureteral stones: a prospective, randomized, controlled study. International Urology and Nephrology. 43 (1), p79-83.
  10.  Fan, B, Yang, D, Wang, J, Che, X, Li, X, Wang, L, et al. (2012). Can tamsulosin facilitate expulsion of ureteral stones? A meta‐analysis of randomized controlled trials. The International Journal of Urology. 20 (8), p818-830.
  11. Picozzi SC, Marenghi C, Casellato S, Ricci C, Gaeta M, Carmignani L. Management of ureteral calculi and medical expulsive therapy in emergency departments. J Emerg Trauma Shock. 2011;4(1):70–76. doi:10.4103/0974-2700.76840
  12. Brede, C, Hollingsworth, J, Faerber,G , Scott Taylor, J, Wolf, J. (2010). Medical Expulsive Therapy for Ureteral Calculi in the Real World: Targeted Education Increases Use and Improves Patient Outcome. Journal of Urology. 183 (2), p585-589.

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