Tamsulosin

Tamsulosin is used to treat the symptoms of an enlarged prostate, also called benign prostatic hyperplasia or BPH. These symptoms include a weak urine stream, trouble starting to urinate, dribbling, a feeling of not emptying the bladder completely, needing to urinate often or urgently, and getting up at night to urinate.

Tamsulosin belongs to a group of medicines called alpha blockers. It works by blocking alpha-1 receptors in the prostate and bladder neck. Blocking these receptors relaxes the muscle there, which improves urine flow and eases BPH symptoms.

Tamsulosin is taken once daily, about half an hour after the same meal each day. Capsules should be swallowed whole and not crushed, chewed, or opened.

The tamsulosin brand name was Flomax, which has now been discontinued in the U.S., but generic tamsulosin is available.

Tamsulosin is not approved to treat high blood pressure, and it is not approved for use in women or children.

Take tamsulosin exactly as prescribed. Follow the directions on your prescription label and read any medication guides or instruction sheets.

• Take once a day, about 30 minutes after the same meal each day. For example, 30 minutes after dinner.
• Swallow the capsule whole. Do not crush, chew, break, or open it.
• If you stop taking tamsulosin for several days, do not start again without talking to your doctor.
• Store at room temperature, away from moisture and heat.

Dosing information

Usual adult dose for benign prostatic hyperplasia:

• 0.4 mg by mouth once a day, taken about half an hour after the same meal each day.
• If symptoms have not improved after 2 to 4 weeks at 0.4 mg, the dose may be increased to 0.8 mg once a day.
• Tamsulosin 0.4 mg should not be taken with a strong CYP3A4 inhibitor such as ketoconazole.
• If tamsulosin is stopped or interrupted for several days, treatment should start again at 0.4 mg once a day.

Do not take tamsulosin if you are allergic to tamsulosin or to any of the ingredients in the capsule.

Do not take tamsulosin with other alpha blockers such as alfuzosin (Uroxatral), doxazosin (Cardura), prazosin (Minipress), silodosin (Rapaflo), or terazosin (Hytrin).

Do not take tamsulosin 0.4 mg with a strong CYP3A4 inhibitor such as ketoconazole. These medicines raise tamsulosin levels in your blood.

Tamsulosin can lower your blood pressure when you stand up, which may make you feel dizzy or faint. This is most likely when you first start taking it, when your dose changes, or when you start it again after a break. Get up slowly from sitting or lying down. Be careful driving or doing anything that needs you to be alert until you know how tamsulosin affects you.

In rare cases (probably fewer than 1 in 50,000 patients), tamsulosin can cause priapism, a painful erection that lasts a long time and is not related to sexual activity. Get medical help straight away if this happens, because without prompt treatment it can lead to permanent erectile dysfunction.

An enlarged prostate and prostate cancer can occur together. Ask your doctor about prostate cancer screening before you start tamsulosin and at regular intervals while you are taking it.

Tamsulosin can cause a problem called intraoperative floppy iris syndrome (IFIS) during cataract or glaucoma surgery. Tell your eye surgeon that you take tamsulosin or have taken it in the past, even if you stopped months ago. Do not stop taking tamsulosin before surgery unless your surgeon tells you to. If you are already booked in for cataract or glaucoma surgery, starting tamsulosin is not recommended.

If you stop taking tamsulosin for several days, talk to your doctor before starting again. You will need to restart at the 0.4 mg dose.

Many other medicines can interact with tamsulosin. Tell your doctor about everything you take, including prescription medicines, over-the-counter medicines, vitamins, and herbal products.

To make sure tamsulosin is safe for you, tell your doctor if you have ever had:

• an allergy to tamsulosin or any of its ingredients
• an allergy to sulfa drugs
• kidney problems
• liver problems
• low blood pressure (hypotension)

Also tell your doctor if you are planning to have cataract or glaucoma surgery.

Ask your doctor about prostate cancer screening before starting tamsulosin and at regular intervals afterwards.

Tamsulosin is not approved for use in women or in children.

Get emergency medical help if you have signs of an allergic reaction, such as hives, itching, rash, swelling of your face, tongue, or throat, or trouble breathing. Rarely, tamsulosin has been linked to severe skin reactions with blistering and peeling of the skin.

Stop taking tamsulosin and call your doctor at once if you have:

• a lightheaded feeling, like you might pass out
• a painful erection that will not go away and is not related to sexual activity

What are the common side effects of tamsulosin?

Common tamsulosin side effects may include:

• headache
• dizziness
• runny or stuffy nose, sore throat, cough, sinus congestion
• flu-like symptoms or infection
• weakness or lack of energy
• back pain, chest pain
• diarrhea, nausea
• drowsiness or trouble sleeping
• tooth problems
• abnormal ejaculation, including a smaller amount of semen or no semen at all
• reduced interest in sex
• blurred vision

Some side effects are more likely at the higher 0.8 mg dose than at the usual 0.4 mg starting dose. In clinical studies, abnormal ejaculation was reported by about 8 in 100 men taking 0.4 mg and about 18 in 100 men taking 0.8 mg. Blurred vision was reported by about 2 in 100 men taking 0.8 mg, and was uncommon at 0.4 mg.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Take the missed dose as soon as you remember. If you have missed the dose for the whole day, skip it and take your next dose at the usual time. Do not take two doses at once.

If you stop taking tamsulosin for several days in a row, talk to your doctor before starting again.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose can cause a serious drop in blood pressure. Lying down flat can help until medical help arrives.

Avoid driving or other activities that could be dangerous until you know how tamsulosin affects you. It can make you feel dizzy or lightheaded.

Avoid getting up too quickly from sitting or lying down, or you may feel dizzy.

Tamsulosin is broken down in the body mainly by two liver enzymes, CYP3A4 and CYP2D6. Medicines that block these enzymes can raise the amount of tamsulosin in your blood and increase the risk of side effects.

Do not take tamsulosin with:

• strong CYP3A4 inhibitors, such as ketoconazole
• other alpha blockers, such as alfuzosin, doxazosin, prazosin, silodosin, or terazosin

Use with caution, and tell your doctor if you take:

• moderate CYP3A4 inhibitors, such as erythromycin
• strong CYP2D6 inhibitors, such as paroxetine, or moderate CYP2D6 inhibitors, such as terbinafine
• cimetidine
• warfarin
• medicines for erectile dysfunction or pulmonary arterial hypertension known as PDE5 inhibitors, including avanafil (Stendra), sildenafil (Viagra, Revatio), tadalafil (Adcirca, Cialis), and vardenafil (Levitra). Taking these with tamsulosin can lower blood pressure enough to cause symptoms.

Some of these cautions matter more at the higher 0.8 mg dose than at 0.4 mg. Your doctor will decide what is right for you.

No dose change is needed if you take tamsulosin with nifedipine, atenolol, enalapril, digoxin, theophylline, or furosemide.

This list is not complete, and many other medicines may interact with tamsulosin. This includes prescription and over-the-counter medicines, vitamins, and herbal products.