If you’re dealing with a small stone (6mm or smaller) in your distal ureter, or have just undergone treatment for your kidney stones, your urologist may recommend oral medications, including Flomax, Azo and Thiazide Diuretics1.

Here’s an easy-to-understand guide to how they work!

Please consult your physician before starting on any of the medications below.


What is Flomax?

Flomax (tamsulosin) belongs to a class of medications known as alpha blockers. Your urologist may prescribe Flomax to enhance spontaneous stone passage, as part of your medical expulsive therapy.

Alpha blockers help to relax the muscles in your ureter, which transports urine from the kidneys to the bladder. By relaxing these muscles, alpha blockers help to decrease the frequency of spasms in your ureter, thereby reducing the pain caused by the passing of your kidney stone. Alpha blockers can also help to increase the speed at which smaller stones pass by up to 30%1.

While you’re on Flomax, you may experience side effects such as runny nose, dizziness, and abnormal ejaculation. Although rare, patients may also develop severe allergic reactions, and men may experience painful and prolonged erections2.

If these symptoms occur, stop taking Flomax and seek immediate medical attention.


What is AZO?

AZO is a medication that is available over-the-counter for urinary pain relief.

AZO can help to manage various conditions associated with urinary pain, including urinary tract infections (UTIs) and kidney stone pain relief. Though AZO’smechanism of action is not fully understood, experts believe it has a pain-relieving effect on the mucosal lining of the urinary tract. While AZO will not help you to pass your kidney stone, it can help to ease stone pain3.

Some common side effects associated with AZO include dizziness, an upset stomach and headaches. Additionally, AZO can cause your urine and tears to turn orange or red, which may stain contact lenses and clothing. Both your tears and urine should normalize in color after stopping AZO3.

Note that AZO should not be taken for more than 2 days in a row, and can complicate existing health conditions. Speak to your physician before getting started on AZO4.


What are thiazide diuretics?

Thiazide diuretics include medications such as chlorthalidone, hydrochlorothiazide, and indapamide.

Though this class of medications can be used for hypertension, it can also be used to assist with kidney stones. Your urologist may prescribe them to lower your urinary calcium5.

Thiazide diuretics work by blocking the sodium-chloride channels in your kidneys, thereby increasing calcium reabsorption in your body6.

If your urinary calcium is high, thiazide diuretics will help to decrease the amount of calcium that enters the urine. They also prevent excessive concentration of calcium phosphate in your urine, and help to normalize your urine pH7.

Although thiazide diuretics may be effective in preventing calcium stones, there are some risks associated with them. Common side effects include fatigue, dizziness, and nausea. Thiazide diuretics are also not intended to be a long-term solution for kidney stones, as they have been associated with a low risk of diabetes with prolonged use8.


In Summary

It is best to be transparent with your doctor about your pre-existing medical conditions, prior to starting a new prescription. If you choose to take a medication for kidney stones, be sure to ask your doctor about how to take it and for how long you should use it!


  1. Teichman, J., Leslie, S. W., Baladato, G., Takacs, E. B., & Schubbe, M. (2019). Medical student curriculum: Kidney stones. Medical Student Curriculum: Kidney Stones. Retrieved April 26, 2022, from https://www.auanet.org/education/auauniversity/for-medical-students/medical-students-curriculum/medical-student-curriculum/kidney-stones

  1. Marconi, M., Pavez, P., San Francisco, I., & Narvaez, P. (2019). Priapism induced by use of tamsulosin: a case report and review of the literature. Archivio Italiano di Urologia e Andrologia91(3)

  2. (2021, February 12). Pyridium (phenazopyridine): Uses, dosage, side effects, interactions, warning. RxList. Retrieved April 26, 2022, from https://www.rxlist.com/pyridium-drug.htm

  3. Norris, R. D., Sur, R. L., Springhart, W. P., Marguet, C. G., Mathias, B. J., Pietrow, P. K., Albala, D. M., & Preminger, G. M. (2008). A prospective, randomized, double-blinded placebo-controlled comparison of extended release Oxybutynin versus phenazopyridine for the management of postoperative ureteral stent discomfort. Urology, 71(5), 792–795 https://doi.org/10.1016/ j.urology.2007.11.004

  4. Cheng, L., Zhang, K., & Zhang, Z. (2018). Effectiveness of thiazides on serum and urinary calcium levels and bone mineral density in patients with osteoporosis: A systematic review and meta-analysis. Drug Design, Development and Therapy, Volume 12, 3929–3935. https://doi.org/10.2147/dddt.s179568

  5. Akbari, P., & Khorasani-Zadeh, A. (2022, January 25). Thiazide diuretics. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK532918/

  6. Coe, F. (n.d.). Thiazide Diuretics for Stone Prevention. Kidney Stone Evaluation And Treatment Program. Retrieved from https://kidneystones.uchicago.edu/thiazide-diuretics-for-stone-prevention/

  7. Zillich, A. J., Garg, J., Basu, S., Bakris, G. L., & Carter, B. L. (2006). Thiazide diuretics, potassium, and the development of diabetes. Hypertension, 48(2), 219–224. https://doi.org/10.1161/01.hyp.0000231552.10054.aa

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