usually [30:<30 mL/minute). 1 7 Concomitant use with potent inhibitors of CYP3A4 (e.g., clarithromycin, itraconazole, ketoconazole, ritonavir). 1 7 (See Interactions.) Warnings/Precautions Warnings Orthostatic Hypotension Potential for orthostatic hypotension, dizziness, or syncope. 1 (See Advice to Patients.) General Precautions Prostate Cancer Exclude possibility of prostate cancer prior to initiation of therapy. 1 Intraoperative Floppy Iris Syndrome Intraoperative floppy iris syndrome (IFIS) observed during phacoemulsification cataract surgery in some patients currently receiving or previously treated with α 1 -adrenergic blocking agents. 1 3 7 8 11 Specifically question male patients being considered for cataract surgery to determine whether they have received silodosin or other α 1 -adrenergic blockers. 1 11 If patient has received α 1 -adrenergic blockers, ophthalmologist should consider modification of the surgical technique through use of iris hooks or iris dilator rings or pharmacologic intervention with intracameral phenylephrine or preoperative administration of atropine to minimize complications of IFIS. 11 Benefit of discontinuing α 1 -blocker therapy prior to cataract surgery not established. 8 11 Specific Populations Pregnancy Category B. 1 Not indicated for use in women. 1 Lactation Not indicated for use in women. 1 Pediatric Use Not indicated for use in children. 1 Geriatric Use Higher incidence of orthostatic hypotension reported in patients 65 years of age compared with younger adults. 1 No other substantial differences in safety and efficacy relative to younger adults. 1 Hepatic Impairment Use not recommended in patients with severe hepatic impairment. 1 7 (See Contraindications under Cautions.) Renal Impairment Use not recommended in patients with severe renal impairment. 1 7 Use caution and reduce dosage in patients with moderate renal impairment. 1 7 Common Adverse Effects Retrograde ejaculation, dizziness, diarrhea, orthostatic hypotension, headache, nasopharyngitis, nasal congestion. 1 4 7 Interactions for Silodosin Extensively metabolized by CYP3A4 and UGT2B7. 1 7 Drugs Affecting Hepatic Microsomal Enzymes Pharmacokinetic interaction (increased plasma silodosin concentrations) with potent inhibitors of CYP3A4. 1 Concomitant use contraindicated. 1 7 Drugs Affecting or Affected by P-glycoprotein Transport Silodosin is a substrate for the P-glycoprotein transport system. 1 Potential pharmacokinetic interaction (increased plasma silodosin concentrations) with inhibitors of P-glycoprotein transport. 1 7 Concomitant use with a potent P-glycoprotein inhibitor not recommended. 1 7 Drugs Affecting Uridine Diphosphate-glucuronosyltransferase (UGT) 2B7 Potential pharmacokinetic interaction (increased silodosin exposure) with inhibitors of UGT2B7. 1 Specific Drugs Drug Interaction Comments α-Adrenergic blocking agents Possible pharmacodynamic interaction 1 Concomitant use not recommended 1 Antihypertensive agents Higher incidence of dizziness and orthostatic hypotension 1 Use with caution; 1 monitor for adverse effects 1 Clarithromycin Increased plasma silodosin concentrations 1 Concomitant use contraindicated 1 Cyclosporine Potential for increased plasma silodosin concentrations 1 Concomitant use not recommended 1 Digoxin No substantial change in digoxin pharmacokinetics 1 Dosage adjustment not required 1 Diltiazem Potential for increased plasma silodosin concentrations 1 Use with caution; 1 monitor for adverse effects 1 Erythromycin Potential for increased plasma silodosin concentrations 1 Use with caution; 1 monitor for adverse effects 1 Fluconazole Potential for increased silodosin exposure 1 Itraconazole Increased plasma silodosin concentrations 1 Concomitant use contraindicated 1 Ketoconazole Substantially increased plasma silodosin concentrations and silodosin exposure 1 Concomitant use contraindicated 1 Phosphodiesterase (PDE) type 5 inhibitors (e.g., sildenafil, tadalafil) Possible orthostatic effects 7 Probenecid Potential for increased silodosin exposure 1 Ritonavir Increased plasma silodosin concentrations 1 Concomitant use contraindicated 1 Valproic acid Potential for increased silodosin exposure 1 Verapamil Potential for increased plasma silodosin concentrations 1 Use with caution; 1 monitor for adverse effects 1 Silodosin Pharmacokinetics Absorption Bioavailability Absolute bioavailability of approximately 32% following oral administration under fed conditions. 1 Peak plasma concentrations attained in about 2.6 hours. 1 Food When administered with a moderate-fat, moderate-calorie meal, AUC and peak plasma concentrations are decreased by 4 49% and 18 43%, respectively, compared with administration in the fasting state. 1 Administration with a high-fat, high-calorie meal not evaluated. 1 Distribution Plasma Protein Binding Approximately 97%. 1 Elimination Metabolism Extensively metabolized in the liver via glucuronidation, alcohol and aldehyde dehydrogenases, and CYP3A4 isoenzymes. 1 The primary active metabolite, KMD-3213G, is formed via UGT2B7-mediated glucuronidation. 1 Another major metabolite, KMD-3293, is formed via alcohol and aldehyde dehydrogenases. 1 KMD-3293 is not expected to contribute substantially to the overall pharmacologic activity of silodosin. 1 Elimination Route Excreted in urine (33.5%) and feces (54.9%). 1 Half-life Approximately 13.3 hours. 1 Special Populations In patients with moderate hepatic impairment, the pharmacokinetics of silodosin were not substantially altered following administration of a single dose. 1 The pharmacokinetics of silodosin in patients with severe hepatic impairment have not been evaluated. 1 In patients with moderate renal impairment, AUC, peak plasma concentrations, and elimination half-life were 3.2, 3.1, and 2 times higher, respectively, than in healthy individuals. 1 In geriatric individuals, AUC and elimination half-life were increased by approximately 15% and 20%, respectively, compared with younger individuals. 1 Stability Storage Oral Capsules 25 C (may be exposed to 15 30 C). 1 Protect from moisture and light. 1 Actions Blocks α 1 -adrenergic receptors in the lower urinary tract to cause relaxation of smooth muscle in the bladder neck and prostate, 1 2 3 4 5 7 resulting in improved urinary flow and reduced symptoms of BPH. 1 3 5 Higher affinity for α 1A -adrenergic receptors, which are in nonvascular smooth muscle (e.g., prostate), than for α 1B -adrenergic receptors located in vascular smooth muscle; 1 2 3 5 may result in reduced incidence of cardiovascular effects (e.g., syncope, dizziness, hypotension). 3 4 5 Advice to Patients Risk of orthostatic hypotension (e.g., feeling faint or dizzy), particularly following initiation of therapy; 1 importance of exercising caution when driving, operating machinery, or performing hazardous tasks. 1 Importance of taking silodosin once daily with a meal. 1 Risk of retrograde ejaculation. 1 Importance of advising patients that this adverse effect occurs frequently and is reversible upon discontinuance of therapy. 1 Importance of advising male patients being considered for cataract surgery that they should inform their ophthalmologist of current or prior α 1 -blocker (e.g., silodosin) therapy. 1 Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses. 1 Importance of informing patients of other important precautionary information. 1 (See Cautions.) Preparations Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details. Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations. Silodosin Routes Dosage Forms Strengths Brand Names Manufacturer Oral Capsules 4 mg Rapaflo Watson 8 mg Rapaflo Watson AHFS DI Essentials. Copyright 2017, Selected Revisions December 1, 2009. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814. References 1. Watson Pharma. Rapaflo (silodosin) capsules prescribing information. Corona, CA; 2008 Oct. 2. Anon. KMD 3213: KAD 3213, Silodosin. Drugs R D . 2004; 5:50-1. 3. Yoshida M, Homma Y, Kawabe K. Silodosin, a novel selective alpha 1A-adrenoceptor selective antagonist for the treatment of benign prostatic hyperplasia. Expert Opin Investig Drugs . 2007; 16:1955-65. [PubMed 18042003] 4. Marks LS, Gittelman MC, Hill LA et al. Rapid efficacy of the highly selective alpha1A-adrenoceptor antagonist silodosin in men with signs and symptoms of benign prostatic hyperplasia: pooled results of 2 phase 3 studies. J Urol . 2009; 181:2634-40. [PubMed 19371887] 5. Kawabe K, Yoshida M, Homma Y et al. Silodosin, a new alpha1A-adrenoceptor-selective antagonist for treating benign prostatic hyperplasia: results of a phase III randomized, placebo-controlled, double-blind study in Japanese men. BJU Int . 2006; 98:1019-24. [PubMed 16945121] 6. Takao T, Tsujimura A, Kiuchi H et al. Early efficacy of silodosin in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia. Int J Urol . 2008; 15:992-6. [PubMed 18775032] 7. Anon. Silodosin (Rapaflo) for benign prostatic hyperplasia. Med Lett Drugs Ther . 2009; 51:3-4. 8. American Urological Association. Guideline on the management of benign prostatic hyperplasia (BPH) (2003/updated 2006). Available from website. Accessed 2009 Aug 13. 9. Madersbacher S, Alivizatos G, Nordling J et al. EAU 2004 guidelines on assessment, therapy and follow-up of men with lower urinary tract symptoms suggestive of benign prostatic obstruction (BPH guidelines). Eur Urol . 2004; 46:547-54. [PubMed 15474261] 10. Watson Pharmaceuticals. Morristown, NJ: Personal communication. 11. Cantrell MA, Bream-Rouwenhorst HR, Steffensmeier A et al. Intraoperative floppy iris syndrome associated with alpha1-adrenergic receptor antagonists. Ann Pharmacother . 2008; 42:558-63. [PubMed 18364408] Next Interactions Print this page Add to My Med List More about silodosin Side Effects During Pregnancy Dosage Information Drug Interactions Support Group En Español 101 Reviews Add your own review/rating Drug class: antiadrenergic agents, peripherally acting Consumer resources Silodosin Silodosin (Advanced Reading) Professional resources Silodosin (Wolters Kluwer) Other brands: Rapaflo Related treatment guides Benign Prostatic Hyperplasia> ]} FEATURED: CAR-T Cell Therapy Overview Mechanism of Action KTE-C19 Studies KTE-C19 Cancer Targets Adverse Events Manufacturing Drug Status Rx Availability Prescription only B Pregnancy Category No proven risk in humans N/A CSA Schedule Not a controlled drug Approval History Drug history at FDA Drug Class Antiadrenergic agents, peripherally acting Related Drugs Benign Prostatic Hyperplasia Cialis , tamsulosin , finasteride , Flomax , doxazosin , terazosin , Proscar , Avodart , prazosin , alfuzosin , tadalafil , Cardura , Rapaflo , dutasteride , Hytrin , Uroxatral , Jalyn , Minipress , dutasteride / tamsulosin , Cardura XL , More... Silodosin Rating 101 User Reviews 6.1 /10 101 User Reviews 6.1 Rate it!} } really appropriate
truly fizzling out Silodosin these days
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