From the FDA Drug Label
Infrequent reports of dyspnea, palpitations, hypotension, atrial fibrillation, arrhythmia, tachycardia, skin desquamation including reports of Stevens-Johnson syndrome, erythema multiforme, dermatitis exfoliative,constipation, vomiting, dry mouth, visual impairment, and epistaxis have been received during the postmarketing period Atrial fibrillation has been reported infrequently in the postmarketing experience with Tamsulosin Hydrochloride Capsules 1. This suggests that atrial fibrillation is a possible adverse reaction associated with the use of Flomax (tamsulosin). However, the causal relationship to drug exposure is not always possible to establish due to the voluntary nature of these reports.
- Key points:
- Atrial fibrillation reported in postmarketing experience
- Infrequent reports
- Causal relationship to drug exposure not always established Note that the FDA label does not provide a clear estimate of the frequency or magnitude of this risk.
From the Research
Flomax (tamsulosin) may cause atrial fibrillation in rare cases, as suggested by recent studies, and patients should be monitored for this potential side effect, especially those with pre-existing cardiovascular conditions. Flomax is an alpha-1 blocker primarily used to treat benign prostatic hyperplasia (BPH) by relaxing muscles in the prostate and bladder neck. While cardiovascular side effects like dizziness and orthostatic hypotension are known with Flomax, atrial fibrillation is not listed among its common side effects. However, a recent study published in 2025 2 highlights that atrial fibrillation can occur as an adverse effect of tamsulosin even in younger patients at lower doses. Another study published in 2022 3 also reports a case of atrial fibrillation with rapid ventricular response in a patient who started taking tamsulosin. The medication works selectively on alpha-1 receptors in the urinary tract rather than directly affecting cardiac conduction.
Some key points to consider:
- The typical dose of Flomax is 0.4 mg once daily, taken approximately 30 minutes after the same meal each day.
- Patients with pre-existing cardiovascular conditions should discuss this medication with their doctor before starting Flomax.
- If you experience heart palpitations, shortness of breath, or chest discomfort while taking Flomax, you should contact your healthcare provider promptly as these could indicate cardiovascular issues requiring medical attention.
- The majority of the evidence suggests that Flomax is effective and well-tolerated in the treatment of BPH, with a low incidence of adverse events, as reported in studies such as 4 and 5.
- However, the most recent and highest-quality study 2 suggests that atrial fibrillation is a potential side effect of tamsulosin, and this should be taken into consideration when prescribing the medication.