Tamsulosin Versus Alfuzosin – What Pharmacists Need to Know

In this blog post, we will compare tamsulosin versus alfuzosin. Tamsulosin and alfuzosin both act on the sympathetic nervous system. Tamsulosin and alfuzosin both work as Alpha₁ antagonists. More specifically, tamsulosin targets the Alpha_1A receptor subtype. Both medications are typically dosed once daily. Tamsulosin is available as an immediate-release capsule, while alfuzosin is available as an extended-release tablet formulation.

Indications

The only FDA-approved indication for both tamsulosin and alfuzosin is for the treatment of benign prostatic hyperplasia. In practice, this is the primary use of each agent. Tamsulosin’s off-label uses include overactive bladder, lower urinary tract symptoms, ureteric stones, urethritis, and neurogenic urinary bladder. Alfuzosin’s off-label uses include hypertension, erectile dysfunction, ureteric stones, and acute urine retention.

Kinetics

The bioavailability of tamsulosin is >90% when taken on an empty stomach. The bioavailability of alfuzosin is 49% when taken with food, and is decreased by 50% if not taken with food. This highlights an important difference between the two medications. Tamsulosin should be taken in a fasted state, while alfuzosin should ideally be taken with food. The protein binding of tamsulosin and alfuzosin, respectively, is 94-99% and 82-90%. Tamsulosin is metabolized through both CYP3A4 and CYP2D6, while alfuzosin is mainly metabolized through CYP3A4. The elimination half-life of both medications is about the same. The elimination half-life for tamsulosin is 9-13 hours, and for alfuzosin is 10 hours. Tamsulosin is primarily excreted renally through urine, while alfuzosin is primarily excreted through feces.

Adverse Effects

The side effect profiles of these agents are similar to each other with some subtle differences. Common side effects of both medications include headache, dizziness, orthostatic hypotension, nausea, and drowsiness. One side effect that is more profound for alfuzosin is dizziness or low blood pressure. This side is more profound to alfuzosin due to it not being as selective as tamsulosin. On the other hand, one side that may be more prevalent for tamsulosin is ejaculation failure.

Clinical Considerations: Tamsulosin Versus Alfuzosin

While general side effects are similar, there are considerations with each of these medications. Alfuzosin has a more prevalent effect on blood pressure (excellent board exam nugget), which results in a higher risk for dizziness and orthostatic hypotension. Alfuzosin should be used with more caution in patients who are at a higher risk for falls, and tamsulosin would be preferred over alfuzosin in these patients. Another consideration is the sexual side effects of tamsulosin. If a patient prefers to avoid this side effect, then alfuzosin would be preferred.

A second consideration is their metabolism. Tamsulosin is metabolized by both CYP3A4 and CYP2D6, while alfuzosin is only metabolized by CYP3A4. In patients where there is higher potential for CYP2D6 drug interactions, alfuzosin may be preferred due to the fewer number CYP enzymes that it is metabolized by.

A third consideration is renal and hepatic impairment. Tamsulosin does not need to be dose-adjusted for creatinine clearance ≥10 mL/min. While alfuzosin has no dose adjustments down to 30 mL/min, it is to be used with caution with creatinine clearance <30 mL/min. For tamsulosin, there are no dose adjustments for patients with hepatic impairment. Alfuzosin’s use is contraindicated in patients with moderate to severe hepatic impairment. Tamsulosin would be preferred over alfuzosin in patients with either severe renal or hepatic impairment. The effectiveness of these agents is comparable, and is not a decisive factor in choosing one medication over the other. Overall, the major deciding factors for choosing one versus the other include their individual side effects, metabolizing enzymes, and severe hepatic or renal impairment. Looking for more on alpha blockers? Check out this post on tamsulosin use in females.

This article was written by Hunter Backholm in collaboration with Eric Christianson, PharmD, BCPS, BCGP

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