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Side Effects of Tamsulosin (Flomax)


Description: Tamsulosin, sometimes referred to by its trade name Flomax, affects chemicals found in the smooth muscle of the bladder, and is frequently used for Benign Prostatic Hyperplasia (BPH), which causes urinary retention. By blocking the activity of these chemicals, Flomax causes smooth muscle to relax, resulting in better urine flow and an improvement in the symptoms of BPH.

Common Side Effects of Flomax

According to the Flomax drug label as reported by the FDA, Flomax is associated with a number of side effects, including:

  • Infections
  • Chest pains
  • Headache (present in 20% of patients)
  • Dizziness
  • Somnolence (sleepiness)
  • Insomnia
  • Abnormal ejaculation
  • Ejaculation disorders including: Retrograde ejaculation and ejaculation failure
  • Rhinitis (presents as stuffy or runny nose)
  • Back pain
  • Diarrhea
  • Pharyngitis (sore throat)
  • Cough
  • Sinusitis
  • Nausea
  • Blurred vision
  • Asthenia (a lack of energy)
  • Decreased libido

    Less Common Side Effects of Flomax

    Rare side effects of tamsulosin, according to the Flomax drug label, include (these occur in less than 1% of patients):

  • Flu
  • Orthostatic hypotension (dizziness when moving from sitting or lying to standing position)
  • Rash
  • Pruritus (itching of the skin)
  • Urticaria (raised rash)
  • Delayed ejaculation
  • Nasal congestion
  • Constipation
  • Vomiting
  • Fatigue

    Understand Your Risks with the Rxight® Genetic Test

    Many patients do not develop adverse effects when taking Flomax; however side effects can be serious in a minority of patients. This interpatient variability may be due to genetic differences between patients. The Rxight® Pharmacogenetic Testing Program is grounded in the sequencing of 18 genes for known variants that interact with more than 200 clinically relevant drugs across 50 medication classes – all with a simple DNA cheek swab at your pharmacy. This allows clinicians to establish how a patient may react when taking medications such as Flomax.

    How Does Pharmacogenetic Testing Work?

    Pharmacogenetics is the study of how medications are metabolized in the body based on genetic variations. It has been suggested that variation in genes that encode for the family of liver enzymes that metabolize a particular drug could increase the probability of developing adverse drug reactions or non-response, depending on how quickly the medication is metabolized. Identifying these gene in patients can aid clinical decision making when physicians and other prescribers are using the drug in treatment. By altering the dose prescribed, physicians may be able to reduce the probability of a patient with a known genetic susceptibility suffering an adverse drug reaction.


    Contributors to this Article:
    Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry


    Read more about Rxight® pharmacogenetics