Rapaflo 8mg Capsules
It is used to treat the signs of an enlarged prostate. If you have been given this drug for some other reason, talk with your doctor for more information.
Drug Class
Alpha-1 adrenergic antagonist
Pharmacologic Class
Selective alpha-1A adrenergic receptor antagonist
Pregnancy Category
Category B
FDA Approved
Oct 2008
DEA Schedule
Not Controlled
Overview
What is this medicine?
Silodosin is a medication used to treat symptoms of an enlarged prostate, also known as Benign Prostatic Hyperplasia (BPH). It works by relaxing the muscles in the prostate and bladder, which helps to improve urine flow and reduce symptoms like frequent urination, urgency, and difficulty starting urination.
How to Use This Medicine
Taking Your Medication
To take this medication correctly, follow your doctor's instructions and read all the information provided. Take the medication with a meal to help your body absorb it properly. If you have trouble swallowing the capsule, you can sprinkle its contents onto a small amount of applesauce. However, do not chew the mixture. Instead, swallow it immediately and follow with a glass of cool water. It's essential to use cool applesauce, as warm applesauce can affect the medication. Do not mix the medication with any other liquids or foods.
Storing and Disposing of Your Medication
To maintain the medication's effectiveness, store it at room temperature, away from direct light and moisture. Keep it in a dry place, such as a closet or drawer, and avoid storing it in the bathroom. Ensure that all medications are kept out of the reach of children and pets to prevent accidental ingestion. If you have unused or expired medication, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist. Check with your pharmacist for guidance on the best way to dispose of your medication, as there may be drug take-back programs available in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember, with a meal. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To take this medication correctly, follow your doctor's instructions and read all the information provided. Take the medication with a meal to help your body absorb it properly. If you have trouble swallowing the capsule, you can sprinkle its contents onto a small amount of applesauce. However, do not chew the mixture. Instead, swallow it immediately and follow with a glass of cool water. It's essential to use cool applesauce, as warm applesauce can affect the medication. Do not mix the medication with any other liquids or foods.
Storing and Disposing of Your Medication
To maintain the medication's effectiveness, store it at room temperature, away from direct light and moisture. Keep it in a dry place, such as a closet or drawer, and avoid storing it in the bathroom. Ensure that all medications are kept out of the reach of children and pets to prevent accidental ingestion. If you have unused or expired medication, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so by your pharmacist. Check with your pharmacist for guidance on the best way to dispose of your medication, as there may be drug take-back programs available in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember, with a meal. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take silodosin once daily with a meal, preferably at the same time each day, to help reduce the risk of dizziness.
- Avoid sudden changes in position (e.g., standing up quickly from a sitting or lying position) to minimize dizziness or fainting.
- Be cautious when driving or operating machinery until you know how this medication affects you, as it can cause dizziness or lightheadedness.
- Avoid alcohol, as it can worsen dizziness and low blood pressure.
- Inform your doctor or eye surgeon that you are taking silodosin if you are scheduled for cataract or glaucoma surgery, as it can cause a condition called Intraoperative Floppy Iris Syndrome (IFIS).
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
8 mg orally once daily with a meal
Dose Range:
8 - 8 mg
Condition-Specific Dosing:
benign_prostatic_hyperplasia:
8 mg orally once daily with a meal
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No dosage adjustment required (CrCl 50-80 mL/min)
Moderate:
Reduce dose to 4 mg orally once daily with a meal (CrCl 30-49 mL/min)
Severe:
Contraindicated (CrCl < 30 mL/min)
Dialysis:
Contraindicated
Hepatic Impairment:
Mild:
No dosage adjustment required
Moderate:
No dosage adjustment required
Severe:
Not recommended; not studied in patients with severe hepatic impairment
Pharmacology
Mechanism of Action
Silodosin is a selective antagonist of alpha-1A adrenergic receptors, which are predominantly located in the prostate, bladder base, bladder neck, prostatic capsule, and prostatic urethra. By blocking these receptors, silodosin causes relaxation of the smooth muscle in these tissues, leading to a decrease in urethral resistance and improvement in urine flow and BPH symptoms.
Pharmacokinetics
Absorption:
Bioavailability:
32%
Tmax:
2.5 hours (fasted), 4.7 hours (with high-fat meal)
FoodEffect:
Administration with a high-fat meal decreases Cmax by approximately 18% and increases Tmax to 4.7 hours, but AUC is not significantly affected. Should be taken with a meal to reduce orthostatic effects.
Distribution:
Vd:
49.5 L
ProteinBinding:
95% (primarily to alpha-1 acid glycoprotein)
CnssPenetration:
Limited
Elimination:
HalfLife:
13.3 hours (silodosin), 24 hours (KMD-3213)
Clearance:
Not available
ExcretionRoute:
Urine (33.5%), Feces (54.9%)
Unchanged:
3.4% (in urine)
Pharmacodynamics
OnsetOfAction:
Within hours to days for symptomatic relief
PeakEffect:
Within 1-2 weeks for maximal symptomatic improvement
DurationOfAction:
24 hours (once daily dosing)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
Orgasm with reduced or absent semen
Dizziness
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
Orgasm with reduced or absent semen
Dizziness
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe dizziness or fainting (syncope)
- Chest pain
- Prolonged, painful erection (priapism) lasting more than 4 hours â seek immediate medical attention
- Allergic reactions (e.g., rash, itching, swelling of face/tongue/throat, severe dizziness, trouble breathing)
- Blurred vision or other eye changes
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the allergic reaction you experienced.
If you have kidney disease or liver disease, as these conditions may affect how your body processes the medication.
Any medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This is crucial because certain medications, such as those used to treat HIV, infections, depression, and other conditions, should not be taken with this drug. Your doctor or pharmacist can help you determine if any of your medications interact with this drug.
If you are using a medication similar to this one, as taking multiple similar medications can increase the risk of adverse effects.
If you are pregnant, plan to become pregnant, or are breastfeeding. This medication is not approved for use in these situations, so it is vital to discuss your options with your doctor.
Please note that this is not an exhaustive list of all potential interactions or health problems that may affect your ability to take this medication. To ensure your safety, it is crucial to:
Inform your doctor and pharmacist about all your medications (prescription and OTC), natural products, vitamins, and health problems.
Verify that it is safe to take this medication with all your other medications and health conditions.
Never start, stop, or change the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the allergic reaction you experienced.
If you have kidney disease or liver disease, as these conditions may affect how your body processes the medication.
Any medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This is crucial because certain medications, such as those used to treat HIV, infections, depression, and other conditions, should not be taken with this drug. Your doctor or pharmacist can help you determine if any of your medications interact with this drug.
If you are using a medication similar to this one, as taking multiple similar medications can increase the risk of adverse effects.
If you are pregnant, plan to become pregnant, or are breastfeeding. This medication is not approved for use in these situations, so it is vital to discuss your options with your doctor.
Please note that this is not an exhaustive list of all potential interactions or health problems that may affect your ability to take this medication. To ensure your safety, it is crucial to:
Inform your doctor and pharmacist about all your medications (prescription and OTC), natural products, vitamins, and health problems.
Verify that it is safe to take this medication with all your other medications and health conditions.
Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
When starting this medication, avoid driving and other activities that require alertness until you understand how it affects you. To minimize the risk of dizziness or fainting, stand up slowly after sitting or lying down, and exercise caution when navigating stairs.
If you are scheduled to undergo cataract surgery or any other eye procedure, discuss this with your doctor beforehand. Adhere to your doctor's recommendations for regular blood tests and other laboratory evaluations. Additionally, monitor your blood pressure as instructed by your doctor.
Men should undergo a rectal exam to check the prostate gland and have a prostate-specific antigen (PSA) test as advised by their doctor. It is also important to consult with your doctor before consuming alcohol.
Note that this medication has been associated with fertility issues in male rats, which resolved after the medication was discontinued. However, it is unclear whether this medication can cause similar fertility problems in humans.
When starting this medication, avoid driving and other activities that require alertness until you understand how it affects you. To minimize the risk of dizziness or fainting, stand up slowly after sitting or lying down, and exercise caution when navigating stairs.
If you are scheduled to undergo cataract surgery or any other eye procedure, discuss this with your doctor beforehand. Adhere to your doctor's recommendations for regular blood tests and other laboratory evaluations. Additionally, monitor your blood pressure as instructed by your doctor.
Men should undergo a rectal exam to check the prostate gland and have a prostate-specific antigen (PSA) test as advised by their doctor. It is also important to consult with your doctor before consuming alcohol.
Note that this medication has been associated with fertility issues in male rats, which resolved after the medication was discontinued. However, it is unclear whether this medication can cause similar fertility problems in humans.
Overdose Information
Overdose Symptoms:
- Severe hypotension (low blood pressure)
- Dizziness
- Fainting (syncope)
- Reflex tachycardia (rapid heart rate)
What to Do:
Call 911 or your local emergency number immediately. Management is supportive, focusing on restoring blood pressure and heart rate. The patient should be kept in a supine position. If necessary, vasopressors and volume expanders may be administered. Dialysis is unlikely to be beneficial due to high protein binding. Call 1-800-222-1222 for Poison Control guidance.
Drug Interactions
Contraindicated Interactions
- Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir, clarithromycin)
- Severe renal impairment (CrCl < 30 mL/min)
- Severe hepatic impairment
Major Interactions
- Other alpha-adrenergic blocking agents (e.g., tamsulosin, alfuzosin, doxazosin, terazosin) - risk of additive hypotensive effects
- PDE5 inhibitors (e.g., sildenafil, tadalafil, vardenafil) - risk of additive hypotensive effects
Moderate Interactions
- Moderate CYP3A4 inhibitors (e.g., diltiazem, erythromycin, verapamil)
- P-glycoprotein inhibitors (e.g., cyclosporine)
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Blood Pressure (sitting and standing)
Rationale: To assess for orthostatic hypotension risk before initiating therapy.
Timing: Prior to first dose
Heart Rate
Rationale: To assess for orthostatic hypotension risk.
Timing: Prior to first dose
Prostate-Specific Antigen (PSA)
Rationale: To rule out prostate cancer, as BPH symptoms can mimic prostate cancer. Alpha-blockers do not affect PSA levels.
Timing: Prior to initiation, if not recently performed
Routine Monitoring
Blood Pressure (sitting and standing)
Frequency: Periodically, especially during initial titration or if symptoms of orthostatic hypotension occur
Target: Maintain within patient's normal range, avoid symptomatic hypotension
Action Threshold: Symptomatic orthostatic hypotension (dizziness, lightheadedness, syncope) or significant drop in BP (e.g., >20 mmHg systolic or >10 mmHg diastolic upon standing)
BPH Symptom Assessment (e.g., AUA Symptom Score)
Frequency: Periodically (e.g., every 3-6 months or as clinically indicated)
Target: Improvement in symptom score
Action Threshold: Lack of symptomatic improvement or worsening symptoms
Symptom Monitoring
- Dizziness
- Lightheadedness
- Orthostatic hypotension
- Syncope (fainting)
- Ejaculatory dysfunction (e.g., retrograde ejaculation)
- Priapism (prolonged erection)
- Chest pain
- Blurred vision
Special Patient Groups
Pregnancy
Silodosin is not indicated for use in women. Pregnancy Category B (based on animal studies showing no harm, but no adequate and well-controlled studies in pregnant women).
Trimester-Specific Risks:
First Trimester:
Not applicable (not indicated for women)
Second Trimester:
Not applicable (not indicated for women)
Third Trimester:
Not applicable (not indicated for women)
Lactation
Silodosin is not indicated for use in women. It is unknown if silodosin is excreted in human milk. Due to the male-specific indication, data on lactation are not available.
Infant Risk:
Not available
Pediatric Use
Safety and effectiveness have not been established in pediatric patients. Silodosin is not indicated for use in pediatric patients.
Geriatric Use
No overall differences in safety or effectiveness were observed between elderly (âĨ65 years) and younger patients. However, the incidence of orthostatic hypotension may be higher in elderly patients, and caution is advised. No dosage adjustment is required based on age alone.
Clinical Information
Clinical Pearls
- Silodosin is highly selective for alpha-1A receptors, which may contribute to its efficacy in BPH symptoms and potentially a lower incidence of cardiovascular side effects compared to non-selective alpha-blockers, though orthostatic hypotension can still occur.
- Retrograde ejaculation (ejaculate going into the bladder instead of out of the penis) is a common and often bothersome side effect, occurring in a significant percentage of patients. Patients should be counseled on this possibility.
- Always take silodosin with a meal to reduce the risk of orthostatic hypotension.
- Patients should be advised to report any prolonged, painful erection (priapism) immediately, as it is a medical emergency.
- Inform ophthalmologists about silodosin use prior to cataract or glaucoma surgery due to the risk of Intraoperative Floppy Iris Syndrome (IFIS).
Alternative Therapies
- Other alpha-adrenergic blockers (e.g., tamsulosin, alfuzosin, doxazosin, terazosin)
- 5-alpha reductase inhibitors (e.g., finasteride, dutasteride) - for larger prostates, can reduce prostate size
- Phosphodiesterase-5 (PDE5) inhibitors (e.g., tadalafil) - for BPH symptoms with or without erectile dysfunction
- Combination therapy (e.g., alpha-blocker + 5-alpha reductase inhibitor)
- Phytotherapy (e.g., Saw Palmetto - efficacy not consistently proven)
- Minimally invasive surgical procedures (e.g., UroLift, Rezum, prostatic urethral lift)
- Surgical procedures (e.g., Transurethral Resection of the Prostate (TURP), simple prostatectomy)
Cost & Coverage
Average Cost:
$30 - $150 per 30 capsules (generic)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 for generic; Tier 3 or higher for brand
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.