Tamosin - Precautions | Dosage | Interactions

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

Tamosin is a medication containing tamsulosin as active substance. It belongs to a family of drugs called alpha-1 blockers. There are three types of alpha-1 receptors, and the prostate contains mostly the alpha-1A receptors (approximately 70%). This drug exhibits an antagonistic effect on alpha-1A and alpha-1D receptors which causes the relaxation of smooth muscles in the prostate and urethra leading to a decrease in the sense of urgency for urination. Because of these effects, Tamosin is used to ease the symptoms of benign prostatic hypertrophy.

This medicine is rapidly absorbed after oral administration and maximum blood concentrations are reached after 4-5 hours if the capsule is taken on an empty stomach or 6-7 hours if taken with/after a meal.

The substantial portion of the drug (94-99%) is bound to plasma proteins. Approximately 70-90% is metabolized via liver cytochrome P450 enzymes while only 5-10% is excreted via the kidneys.


Tamosin should not be used in patients who have:

  • Severe hepatic impairment
  • Known hypersensitivity to tamsulosin
  • Hypotension.

Caution must be exercised in patients who have renal impairment, as well as in patients with eye disorders.

In studies that investigated the co-administration of this drug with antihypertensive agents (e.g. nifedipine, enalapril and atenolol), Tamosin did not affect the efficacy of antihypertensive agents, and a dose adjustment is not necessary when this medicine is administered concomitantly with antihypertensive drugs. However, most doctors recommend caution if Tamosin is administered concomitantly with antihypertensive drugs and regular monitoring of blood pressure during the first month of therapy.

Studies have shown that the symptoms of orthostatic hypotension (dizziness and sudden loss of consciousness when getting up quickly) are more common in patients taking this medicine than in patients who have been on placebo. For this reason, patients who have a history of syncope should cautiously apply this medication.

Adverse effect called priapism characterized by long-lasting and painful erections that are not associated with sexual activity have been reported in less than 0.05%. Priapism can lead to permanent impotence, which is why patients are advised to call their doctor as soon as possible if they notice symptoms of priapism.

Since Tamosin has a certain chemical similarity with sulfonamides, patients with known hypersensitivity to sulfonamides may develop an allergic reaction to Tamosin, and hence the use of this drug in such patients is not recommended.

Due to the possible occurrence of hypotension and vertigo, patients are advised to avoid driving the motor vehicles and operating machinery while taking this medication.

Tamosin should not be used in patients under the age of 18 due to the lack of data on the safety of its use in this population.


The recommended dose is 0.4 mg (one tablet) once a day, after breakfast. If there is no symptoms improvement after one month of therapy, the dose should be increased to 0.8 mg once a day.


Tamosine should not be administered concurrently with the following medicines:

  • Other alpha blockers, such as: alfuzosin (Xatral SR), doxazosin and terazosin. Although there are no clinical studies to confirm the seriousness of the interaction between these drugs, the interaction is very likely to occur due to an identical mechanism of action.
  • Medicines used to treat HIV (e.g. indinavir, ritonavir, saquinavir, atazanavir, fosempranavir, lopinavir, and amprenavir). These drugs significantly increase plasma levels of Tamosin, which increases the risk of adverse reactions.
  • Macrolide antibiotics, such as: clarithromycin, azithromycin, erythromycin, and telithromycin.
  • Antifungal drugs, such as: voriconazole, posaconazole, ketoconazole, and itraconazole.

Adverse reactions

Possible adverse reactions of Tamosin include:

  • Cough
  • Infections
  • Dizziness
  • Headache
  • Back pain
  • Chest pain
  • Blurred vision
  • Sinusitis
  • Palpitations
  • Hypotension
  • Asthenia
  • Priapism
  • Steven-Johnson syndrome
  • Atrial tachycardia
  • Unnatural ejaculation
  • Rash
  • Itchy skin
  • Hives


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