Alpha-blockers (i.e., tamsulosin) are commonly seen in male patients, as they are used to treat symptoms of benign prostatic hyperplasia (BPH; the only FDA-approved indication currently). Because of this, there is no doubt a prescription sent to the pharmacy for a female may raise some speculation. In recent years, uroselective alpha-blockers have been used for the management of kidney stones. All agents in this class have been found to be effective, although most of the data is regarding tamsulosin. Below, we discuss kidney stones, tamsulosin use in females, and why you might not need to call the doctor for clarification.

Kidney stones are common and have only been increasing in prevalence. They are crystalline concretions formed as a result of solute precipitation in the setting of urine supersaturation. 80% of patients will form calcium stones, however, there are multiple different constituents capable of crystallization and sometimes stones will contain more than one type. Several factors can increase the concentration of calcium or oxalate in the urine, including diet, intestinal bypass surgery, and metabolic disorders. Medications may also increase the risk of calcium phosphate stone development, particularly drugs that alter carbonic-anhydrase function such as acetazolamide and topiramate. A broad review of kidney stone composition and likely association include the following:

• Calcium oxalate; likely caused from diet or intestinal bypass surgery
• Calcium phosphate; seen in metabolic disorders or with carbonic anhydrase inhibitors
• Magnesium ammonium phosphate (AKA struvite); seen in infectious stones
• Uric acid; typically idiopathic or from hypovolemia
• Cystine; result of genetic defect

Kidney stones can be asymptomatic when they are limited to the kidney. Pain typically develops when the stone travels through the genitourinary system, from the kidney, and down the ureters. The pain is often described as dull initially but can progress to sharp, and severe. Blood in the urine is not uncommon from larger stones damaging the ureter walls. Several complications may arise from kidney stones, including but not limited to infection, abscess formation, ureteral perforation, and renal function loss from long-standing obstruction.

As far as treatment goes, the primary goal is pain control with non-steroidal anti-inflammatory drugs (NSAIDs) to help relieve ureteral spasms. Tamsulosin was noticed to aid stone passage by reducing smooth muscle stimulation, therefore was designated as medical expulsive therapy (MET) along with calcium channel blockers (i.e., nifedipine) and antispasmodic agents. MET therapies are used to increase the passage rate of kidney stones. There has been some data to suggest better efficacy from tamsulosin over nifedipine, so it is typically used more often. Tamsulosin also has less concern for hypotension given its uroselectivity. It is currently recommended to treat with tamsulosin 0.4 mg daily for up to 4 weeks in kidney stones >5 mm and ≤10 mm, in all adults. This is why you will see tamsulosin use in females!

While kidney stones are likely the answer for tamsulosin use in females, there has been emerging data in the treatment for lower urinary tract symptoms (LUTS). Randomized controlled trials with tamsulosin vs. placebo have seen improvements in overactive bladder and quality of life questionnaires, along with physiological improvements in urine flow rate. This is currently used off-label, but you may see prescriptions for tamsulosin 0.4 mg daily for these reasons. 

Have you seen any other unusual cases with tamsulosin? I hope this review saves you time from calling the clinic for clarification!

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This article was written by Hannah Wetter in collaboration with Eric Christianson, PharmD, BCPS, BCGP

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Resources:

1. Curhan, G., et al. Kidney stones in adults: Diagnosis and acute management of suspected nephrolithiasis. UpToDate [Web]. Wolters Kluwer Health. Waltham, MA. Last updated January 2022. Accessed via https://www.uptodate.com/contents/kidney-stones-in-adults-diagnosis-and-acute-management-of-suspected-nephrolithiasis?search=kidney%20stones&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1
2. Koski, R. Efficacy and Safety of Alpha-Blockers for Kidney Stones in Adults. Published 2018; 34(2): 54-61. 
3. Nojaba, L., Guzman, N. Nephrolithiasis. StatPearls [Internet]. Last updated August 2021. Accessed via https://www.ncbi.nlm.nih.gov/books/NBK559227/
4. Zhang, H.L., et al. Tamsulosin for treatment of lower urinary tract symptoms in women: a systematic review and meta-analysis. International Journal of Impotence Research. Published 2017; 29: 148-156.