Tamsulosin - Dosage | Overdose | Interactions

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Tamsulosin is a medicine that belongs to the group of alpha-1 antagonists and is used to alleviate the symptoms of prostate enlargement.


Tamsulosin should be avoided in patients with low blood pressure (hypotension). Postural (orthostatic) hypotension may occur in patients who are treated with this drug. Avoid sudden rising from a lying or sitting position while on therapy with this drug, because it increases the risk of postural hypotension.

You need to inform your ophthalmologist that you are taking this medicine as this medication may cause intraoperative floppy iris syndrome, which can complicate the cataract. In case you're planning cataract surgery, you need to stop taking this drug fifteen days prior procedure.

Prior starting Tamsulosin, it is recommended to rule out other diseases that can cause identical symptoms as enlarged prostate. It is best to determine the level of prostate-specific antigen (PSA) in the blood prior starting therapy.

In general, so far it has not been established that this medicine interacts with drugs used for the treatment of hypertension, but caution is recommended due to the possible additive hypotensive effects.


The recommended dosage is one capsule per day (0.4 mg) for half an hour after breakfast.

Do not chew, crush or crumble capsules because this will impair the effectiveness of this drug.

Swallow the capsule whole with 8 fl. oz. of plain or mineral water.

It should not be applied concurrently with alcoholic beverages.


The most typical and most important sign of an overdose is hypotension. Overdose treatment include with the application of a plasma expander or vasopressor drugs. Performing gastric lavage or taking activated charcoal may also be useful.


Tamsulosin may interact with the following medicines:

Medicine Result of interaction



Increased elimination rate and decreased efficiency of Tamsulosin

Antifungal drugs (voriconazole, itraconazole, fluconazole, and ketoconazole)

HIV protease inhibitors (amprenavir, indinavir, saquinavir, and tenofovir, cobicistat, boceprevir, and others)

Inhibition of enzymes which metabolize Tamsulosin, leading to increase in the plasma concentration of this medicine. All this leads to increased risk of postural hypotension.
Mibefradil (medicine for high blood pressure)
Idelalisib (drug for the treatment of chronic lymphocytic leukemia)
Nefazodone (antidepressant)

Side effects

The potential adverse effects of this drug are given in the table below:

Common (occurring in 1-10% of patients) Occasional (affects 0.1-1% of the patients) Rare (occurring in 0.1-0.01% of patients) Very rare (occurring in less than 0.01% of patients)
Dizziness Rhinitis Sudden loss of consciousness Priapism
Ejaculation disorders Palpitations Angioedema Stevens-Johnson syndrome
Cough Postural hypotension Feeling of constant movement of self Increased sweating
Back pain Asthenia Decreased libido Itching
Fever Urticaria Inability to maintain an erection Muscle ache
Painful urination Headache Pain around eyes Pain in the joints
Trouble urination Diarrhea or constipation Tooth disorders Redness eye


  1. PIL

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