Silodosin (Rapaflo)

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Silodosin (Rapaflo)

Used for Benign Prostatic Hyperplasia (BPH), or “Enlarged Prostate”

Silodosin is taken daily for relief of obstructive and irritative voiding symptoms. Obstructive symptoms include slow / weak stream, start/stop stream, or incomplete emptying. Irritative symptoms include frequency, urgency, and waking up at night to urinate (nocturia). This medication is very similar to tamsulosin (Flomax) but generally is more well tolerated due to less side effects.

How Silodosin (Rapaflo) works

Silodosin (Rapaflo) is an alpha-1A blocker. It selectively blocks a smooth muscle receptor found in the tissue of the prostate and bladder opening. By blocking these receptors, the medication encourages relaxation of the smooth muscle cells in your prostate and bladder opening, which relieves symptoms of BPH by making it easier to urinate.

Typical dosing for Silodosin

  • The typical dose is 8 mg daily with a meal 
  • It is also available in 4 mg pills

mensRxplus Recommendations:

  1. Take Silodosin (Rapaflo) at about the same time every day to have the most consistent results. It is recommended to take with a meal.

Side Effects:

Common Side Effects

  • Retrograde ejaculation (orgasm with less or no semen; 28%)
  • Dizziness (3%)
  • Diarrhea (3%)
  • Drop in blood pressure when standing from a seated or lying down position (3%)

Less common side effects can include: headache, congestion, runny nose, trouble sleeping, stomach pain. 

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Drug Interactions

Silodosin (Rapaflo) interaction with other drugs:

Take care when taking medications that could lower blood pressure as there is an increased risk of dizziness. Your doctor may need to lower the dose of one of your blood pressure medications if you start taking Silodosin (Rapaflo).  Do not take with other alpha-blocker medications used for blood pressure and / or BPH (Terazosin, Prazosin, Tamsulosin) as they could have compounding side effects. 

It is commonly not recommended to take Silodosin with medications used for ED, such as (Sildenafil) Viagra or Tadalafil (Cialis).  However in reality there are many men who have both BPH and ED. Discuss with your doctor, or consider taking daily Cialis if you have both BPH and ED. 

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.



  • Atazanavir
  • Boceprevir
  • Clarithromycin
  • Cobicistat
  • Idelalisib
  • Indinavir
  • Itraconazole
  • Ketoconazole
  • Nefazodone
  • Nelfinavir
  • Ritonavir
  • Saquinavir
  • Telithromycin

Frequently Asked Questions

Silodosin (Rapaflo) starts working immediately. Most men will notice a benefit within days. 

Silodosin (Rapaflo) causes relaxation of the smooth muscle in the bladder opening.  This area is normally closed tight during ejaculation so that all the ejaculatory fluid goes towards the tip of the penis. When the bladder opening is slightly relaxed, the pressure of ejaculation may cause some of the ejaculatory fluid to go the other direction, so it ends up in the bladder. This is harmless, and it will come out with urination. 

Tamsulosin (Flomax) has been around longer than Silodosin (Rapaflo) so many medical providers are used to always prescribing Tamsulosin first. Also Tamsulosin tends to be slightly cheaper than Silodosin, so it is often the preferred drug from insurance companies. Silodosin has similar efficacy to tamsulosin, meaning it works just as well, and generally is more well tolerated by men. It tends to be slightly more expensive, including as a generic mensRxplus.com. 

Warnings

Silodosin (Rapaflo) should not be taken in men with:

Eye problems

This issue is a concern for patients who have a planned eye surgery for cataract or glaucoma. Silodosin (Rapaflo) can cause an eye problem called floppy iris syndrome (FIS), which can raise your risk of having eye problems during and after eye surgery. If you have planned eye surgery talk to your eye provider before starting Silodosin (Rapaflo), or if you are already taking make sure to inform them, as they may need to adjust their surgical technique.

Low Blood Pressure:

Silodosin (Rapaflo) can lower your blood pressure. This is more likely if you already have low blood pressure, take blood pressure lowering medications, or are taking PDE-5 inhibitory drugs such as Viagra or Cialis. 

When you first start to take Silodosin (Rapaflo) or if your dose is increased, you can experience a sudden drop in blood pressure when you get up from a sitting or lying down position. This is called orthostatic hypotension, and symptoms include feeling light headed or dizzy, blurry vision, fainting, nausea, and confusion. Always make sure to move slowly from a lying down position to a sitting position, and then stand up slowly to allow your body to adjust to possible changes in blood pressure. Your body should adjust to the medication after the first few days, but if you continue to have these symptoms tell your healthcare provider. If you fall and hit your head, get medical help right away.

  • Risk factors: Moving too quickly from sitting down to standing up | Not enough fluid in your body (dehydration) | Taking other medications that lower blood pressure | Heart failure | Drinking alcohol, Taking PDE-5 inhibitor medication such as Viagra or Cialis

Higher risk for side effects in people with kidney problems

Because silodosin (Rapaflo) is metabolized by the kidneys, you might be at higher risk of side effects from silodosin (Rapaflo) if you have kidney problems. When your kidneys don’t work as well as they should, your body can’t get rid of the medication from your system as well. As a result, the medication can build up in your body and raise your risk for toxicity. Let your provider know before starting silodosin (Rapaflo) if you have kidney problems, namely Chronic Kidney Disease (CKD stage I, II, or III). Your provider might recommend a low dose for you to lower your risk for side effects (the 4 mg dose) if you have kidney impairment, but if you have sever kidney disease you can not take Silodosin (Rapaflo).

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