Tamsulosin: 7 things you should know
Medically reviewed by C. Fookes, BPharm Last updated on Oct 7, 2019.
1. How it works
- Tamsulosin is used to improve urine flow in men with benign prostatic hyperplasia (BPH) (also called an enlarged prostate gland).
- The symptoms of BPH occur as a result of an increase in the size of the prostate as well as an increase in the tone of the muscle (as a result of muscle contraction mediated by alpha1 receptors) in the prostate and neck of the bladder. Both of these factors cause a constriction of the bladder outlet, which disrupts urine flow. Tamsulosin blocks alpha1 receptors located in and around the prostate, the top of the urethra, and the neck of the bladder, which reduces muscle tone. As a result urine flow rates are improved and there is a reduction in the symptoms of BPH.
- Tamsulosin belongs to a class of drugs known as alpha-adrenergic blockers.
- Tamsulosin may be used in the treatment of benign prostatic hypertrophy to improve urine flow rates and other symptoms such as hesitancy, incomplete bladder emptying, intermittency, and a weak urine stream.
- No dosage adjustment is required in men with kidney or liver disease (however, the use of tamsulosin in men with end-stage kidney disease or severe liver disease has not been studied).
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Dizziness, headache, a runny nose, drowsiness, and sexual dysfunction (abnormal ejaculation).
- May cause orthostatic hypotension (a drop in blood pressure when going from sitting to a standing position). This is more likely during tamsulosin initiation, or when increasing the dose. Vertigo and syncope (a temporary loss of consciousness) may also occur.
- Rare cases of priapism (painful erections more than 4 hours in duration) have been reported.
- May not be suitable for people undergoing cataract or glaucoma surgery, in those with severe kidney or liver disease, or in people with a history of low blood pressure.
- Rarely, may cause a reaction in people with a sulfa allergy.
- May interact with a number of other drugs including strong inhibitors of CYP3A4 hepatic enzymes (such as ketoconazole), inhibitors of CYP2D6 (such as paroxetine), PDE5 inhibitors (such as sildenafil [Viagra]), or warfarin.
- Tamsulosin should not be used in women or children.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Administer at the same time each day, half an hour after the same meal (for example, half an hour after breakfast). Take exactly as directed by your doctor. Do not increase or decrease the dosage without his or her advice.
- Do not crush, chew, or open tamsulosin capsules.
- If, for any reason, you need to stop taking tamsulosin capsules for a few days, you should restart therapy with the 0.4mg dose, even if you have been taking the 0.8mg dose. Talk to your doctor about this.
- Stand up slowly when going from a sitting or lying down position. Tamsulosin may cause a drop in blood pressure which may cause symptoms such as dizziness and increase your risk of falls. Remove any fall hazards in your home (such as rugs) and talk to your doctor if you are experiencing severe dizziness every time you stand up.
- Do not drive or operate machinery if tamsulosin makes you dizzy or impairs your judgment. Alcohol may enhance this effect and is best avoided.
- Seek urgent medical advice if you develop any symptoms of an allergic reaction such as swelling of the face, tongue, or throat; difficulty breathing; or a skin rash.
- It is not uncommon for prostate cancer to coexist with BPH. Talk to your doctor about screening for prostate cancer.
- Talk to your doctor or pharmacist before taking any other medications while you are taking tamsulosin.
6. Response and Effectiveness
- Peak concentrations of tamsulosin are reached within four to five hours when a tamsulosin capsule is taken on an empty stomach, or within six to seven hours when tamsulosin is taken with food.
- For most people, the 0.4mg dose of tamsulosin is sufficient. If there is no response to the 0.4mg dose after two to four weeks of taking, tamsulosin may be increased to 0.8mg per day. However, this may result in an increase in the risk of side effects such as dizziness when standing.
- It may take up to five days of regular dosing before the full effects of tamsulosin on urine flow are achieved.
Medicines that interact with tamsulosin may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with tamsulosin. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with tamsulosin include:
- antibiotics such as clarithromycin, erythromycin, or doxycycline
- antidepressants, such as fluoxetine, paroxetine, St John’s Wort, monoamine oxidase inhibitors, and tricyclic antidepressants (such as amitriptyline, imipramine, and nortriptyline)
- antifungals, such as itraconazole and ketoconazole
- antihistamines, such as diphenhydramine
- beta-blockers such as atenolol or metoprolol
- CYP3A4 or CYP2D inducers or inhibitors
- HIV medications such as ritonavir
- other alpha-blockers such as prazosin or terazosin
- some medications used to treat mental illness, such as clozapine or thioridazine
- some heart medications, such as amiodarone, clonidine, digoxin, diltiazem, propafenone, quinidine, and verapamil
- NSAIDs, such as diclofenac, ibuprofen, and indomethacin, may decrease the blood pressure-lowering capabilities of tamsulosin.
Note that this list is not all-inclusive and includes only common medications that may interact with tamsulosin. You should refer to the prescribing information for tamsulosin for a complete list of interactions.
Tamsulosin. Revised 08/2019. Drugs.com https://www.drugs.com/ppa/tamsulosin.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use tamsulosin only for the indication prescribed.
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- Drug class: antiadrenergic agents, peripherally acting
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