Silodosin

Trade Names:
Rapaflo
- Capsules 4 mg
- Capsules 8 mg

Pharmacology

User Reviews & Ratings As a treatment for... Avg User Ratings [?] Benign Prostatic Hyperplasia 6 reviews Rate it! 6.0 Compare with other drugs.

Selectively blocks postsynaptic alpha-1 adrenoreceptors located in the prostate, bladder base, prostatic capsule, and prostatic urethra.

Pharmacokinetics

Absorption

AUC is 373.4 ng•h/mL. C _max is 61.6 ng/mL. T _max is 2.6 h. Absolute bioavailability is about 32%.

Distribution

Vd is 49.5 L. Approximately 97% is protein bound.

Metabolism

Extensively metabolized through glucuronidation, alcohol and aldehyde dehydrogenase, and CYP3A4 pathways. The major metabolite is pharmacologically active.

Elimination

Half-life of silodosin is 13.3 h, and that of the major metabolite is about 24 h. Excretion is 54.9% in feces and 33.5% in the urine.

Special Populations

AUC, C _max , and elimination half-life are increased in patients with moderate renal impairment.

Pharmacokinetics not altered in patients with moderate hepatic impairment. Patients with severe hepatic impairment have not been studied.

Exposure and elimination half-life are approximately 15% and 20%, respectively, more in subjects with a mean age of 69 yr compared with subjects with a mean age of 24 yr.

Indications and Usage

Treatment of signs and symptoms of benign prostatic hyperplasia (BPH).

Contraindications

Severe renal impairment (CrCl less than 30 mL/min); severe hepatic impairment (Child-Pugh score 10 or more); coadministration with strong CYP3A4 inhibitors (eg, clarithromycin; itraconazole, ketoconazole, ritonavir).

Dosage and Administration

PO 8 mg once daily with a meal.

PO Renal impairment (CrCl 30 to 50 mL/min): 4 mg once daily with a meal.

General Advice

• Take with food.

Storage/Stability

Store at 59° to 86°F. Protect from light and moisture.

Drug Interactions

Additive pharmacologic effects and adverse reactions may occur. Avoid coadministration with silodosin.

Use with caution. The risk of dizziness and orthostatic hypotension may be increased.

Silodosin plasma concentrations may be elevated, increasing the pharmacologic effects and adverse reactions. Use with caution.

The risk of dizziness and orthostatic reactions may be increased.

Silodosin plasma concentrations may be elevated, increasing the pharmacologic effects and adverse reactions. Coadministration with silodosin is contraindicated.

Silodosin exposure may be increased. Coadministration with silodosin is not recommended.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Orthostatic hypotension (3%).

CNS

Dizziness (3%); headache (2%); asthenia, insomnia (1% to 2%).

Dermatologic

Purpura, toxic skin eruption (postmarketing).

EENT

Nasal congestion, nasopharyngitis (2%); rhinorrhea (1% to 2%).

GI

Diarrhea (3%).

Genitourinary

Retrograde ejaculation (28%); increased prostate-specific antigen (1% to 2%).

Hepatic

Impaired hepatic function associated with increased transaminase values, jaundice (postmarketing).

Respiratory

Sinusitis (1% to 2%).

Miscellaneous

Abdominal pain (1% to 2%).

Precautions

Pregnancy

Category B .

Lactation

No information provided.

Children

Safety and efficacy not established.

Elderly

Risk of orthostatic hypotension may be increased.

Renal Function

Plasma concentrations were approximately 3-fold higher and the half-life was prolonged 2-fold in individuals with moderate renal impairment. Use with caution and in reduced dose in patients with moderate renal impairment.

Hepatic Function

Contraindicated in individuals with severe hepatic impairment. No dosage adjustments are needed in patients with mild or moderate hepatic impairment.

Cognitive and motor impairment

Caution patients about driving, operating machinery, or performing hazardous tasks when initiating therapy.

Floppy iris syndrome

Intraoperative floppy iris syndrome has been reported during cataract surgery in patients receiving or previously treated with alpha-1 blockers.

Orthostatic hypotension

Postural hypotension, with or without symptoms, may occur at the beginning of treatment.

Prostate cancer

Rule out before starting therapy.

Overdosage

Symptoms

Postural hypotension.

Patient Information

• Caution patients about driving, operating machinery, or performing hazardous tasks when initiating therapy.
• Instruct patients to take product with food.
• Instruct patients to inform ophthalmologist about the use of silodosin before cataract surgery or other procedures involving the eye, even if the drug has been discontinued.

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