7 Flomax (Tamsulosin) Side Effects: How to Manage Headaches, Dizziness, and More

If you’re living with benign prostatic hyperplasia (BPH), a number of medications can help you manage inconvenient urinary symptoms. Flomax (tamsulosin) is a daily choice for many people.

Flomax is a type of alpha blocker. It’s designed to make it easier to urinate by relaxing the muscles around the prostate and bladder, among other effects. This helps manage BPH symptoms, but it’s not a cure. And like any medication, Flomax can cause side effects. But its side effect risks are generally lower compared with similar medications.

Flomax side effects at a glance

Many Flomax side effects are mild and can be managed at home. More serious side effects are possible, but they are less common.

Common Flomax side effects (reported by at least 4% of people during clinical trials) include:

• Headache

• Cold and flu symptoms, such as a runny or stuffy nose, sore throat, and cough

• Weakness

• Back pain

• Dizziness

• Diarrhea

• Chest pain

• Sleepiness

• Abnormal ejaculation

Less common but potentially serious Flomax side effects include:

• Blood pressure changes, which can result in fainting

• Priapism (erection lasting over 4 hours)

• Floppy iris syndrome

EXPERT PICKS: WHAT TO READ NEXT

• Flomax interactions: Flomax (tamsulosin) can interact with certain medications, supplements, and even alcohol. Here’s a list of tamsulosin interactions and how to manage them.

• What to avoid: Some common medications can worsen symptoms of an enlarged prostate. Learn which ones to steer clear of and how they might affect your condition.

• Know your options: Managing an enlarged prostate often starts with the right medications. Discover the most effective medication options and how they work.

Allergic reactions to Flomax are rare but possible. This is especially the case if you have a sulfa allergy. If you’re allergic to antibiotics such as Bactrim (sulfamethoxazole / trimethoprim), you may react to Flomax as well. Make sure your healthcare team has a list of your drug allergies before you start Flomax.

Next, we’ll cover practical tips for managing seven Flomax side effects.

1. Headache

Headaches are one of the most common Flomax side effects. They tend to happen because Flomax can widen your blood vessels and increase blood flow in certain parts of your body. This can cause headaches for some people. But they tend to get better as your body adjusts to the medication.

If you find headaches to be bothersome while taking Flomax, here are some tips for managing them:

• Stay hydrated by drinking water throughout the day. But try to limit how much you drink before bed to avoid nighttime bathroom trips.

• Avoid or minimize caffeine and alcohol, which can worsen headaches.

• Ask a pharmacist about over-the-counter (OTC) pain relievers that are safe for you to take.

• Practice stress-relief techniques, such as deep breathing or light exercise.

Talk to your prescriber if your headaches are severe or persistent or affecting your quality of life. They may be able to adjust your dosage or suggest alternative treatments.

2. Dizziness

Dizziness is another common Flomax side effect. It can happen because Flomax relaxes blood vessels, which can cause a drop in blood pressure. Some people may feel dizzy or lightheaded when they stand up from a sitting or lying position. This effect tends to be more intense among older adults, when you first start Flomax, and after your dose is increased.

Here are a few tips to manage dizziness from Flomax:

• Stand up slowly from a sitting or lying position to give your body time to adjust.

• Sit or lie down immediately if you feel lightheaded to prevent falls.

• Take Flomax in the evening to reduce the risk of dizziness during the day and injury from an accidental fall. Dizziness is less of an issue if you’re asleep or lying down.

• Share your medication list with your healthcare team. They can check for interactions that may worsen dizziness.

If your dizziness persists or becomes bothersome, your prescriber may need to adjust your treatment plan.

3. Ejaculation issues

Flomax can change how you ejaculate. Some men report experiencing anejaculation, or no ejaculation during sexual activity. Ejaculation issues are more likely to occur with higher doses of Flomax.

Very few men report experiencing pain or discomfort from this side effect. Issues with sexual performance or desire (libido) are also rare. So if you experience erectile dysfunction or any changes in libido, it’s important to tell your healthcare team.

4. Runny or stuffy nose

A runny nose is another common Flomax side effect, especially with higher doses. Nasal congestion is also possible, but it tends to be less common. These side effects can happen on their own, but they can also be a sign you’re getting sick. In fact, infections (such as the flu and common cold) were more common with Flomax during clinical trials.

If you have a runny or stuffy nose, here are a few tips to help you find relief:

• Use a saline nasal spray. Saline sprays can help clear your nasal passages. Nasal saline rinses are another option.

• Talk to your pharmacist. They can suggest OTC remedies to help manage your symptoms. It’s a good idea to steer clear of decongestants like Sudafed (pseudoephedrine) and Afrin (oxymetazoline). They work fast for congestion but can worsen BPH symptoms.

• Use a humidifier. Adding moisture to the air can soothe nasal passages, thin mucus, and reduce dryness.

If you think you’re coming down with something and home remedies aren’t helping, tell your healthcare care. Treatments are available if it’s the flu or COVID-19. Or you may need an antibiotic if your infection is caused by bacteria.

5. Blood pressure changes

Flomax can sometimes cause a drop in blood pressure, especially when changing positions. This tends to be most noticeable after taking your first Flomax dose. If this happens, you may feel dizzy or lightheaded.

Taking Flomax with certain medications can also cause your blood pressure to drop dangerously low (called hypotension). Examples of these medications include:

• Erectile dysfunction medications, such as sildenafil (Viagra) and tadalafil (Cialis)

• Other alpha blockers, such as doxazosin (Cardura)

• Blood pressure medications, such as lisinopril (Zestril, Qbrelis)

• Nitrates, such as nitroglycerin (Nitrostat, Nitromist)

The same tips for managing dizziness apply here, including taking your dose at night and moving slowly when getting up. It’s a good idea to share an updated list of medications and supplements you take with your healthcare team. They can screen for interactions that increase the risk of hypotension with Flomax and make adjustments as needed.

6. Floppy iris syndrome

Floppy iris syndrome is a funny name for a potentially serious side effect. It can weaken or loosen the muscles that control how much light enters your eyes.

This Flomax side effect doesn’t make a big difference in daily life, but it can come into play if you need eye surgery. With a “floppy” iris, surgeons have a hard time predicting the movements of the eye during surgery. This can lead to complications.

Eye surgery may be necessary for a number of conditions, including cataracts. If you’re planning on having eye surgery, be sure to tell your surgeon about your Flomax prescription before the procedure starts. The surgeon may change which medications and techniques they use during the surgery.

7. Chest pain

Chest pain (angina) has been reported by people taking Flomax. It may be more likely if you’re also taking heart medications, but it can occur for various reasons. Chest pain should always be taken seriously.

Chest pain can be a symptom of a serious medical problem. As a precaution, you should tell your healthcare team if you have new or worsening chest pain while taking Flomax. But there are certain situations when you should seek emergency care, including:

• Your chest pain is severe, persistent, or getting worse.

• You also have symptoms such as shortness of breath, cold sweats, or nausea.

• The pain travels to your jaw, neck, arms, or back.

• The pain gets worse when you move or do physical activity.

Frequently asked questions

Why trust our experts?

Written by:

Nathan Williams, PharmD, RYT

Nathan is a clinical pharmacist, certified yoga instructor, and medical content writer. His clinical practice has spanned several sub-specialties including: emergency medicine, nutrition, and pediatrics.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Our editorial standards

Meet our experts