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warnings and cautions
5 WARNINGS AND PRECAUTIONS Postural hypotension, with or without symptoms (e.g., dizziness), may develop when beginning silodosin treatment. ( 5.1 ) In patients with moderate renal impairment, silodosin dose should be reduced to 4 mg once daily. ( 5.2 ) Silodosin should not be used in combination with other alpha-blockers. ( 5.5 ) Examine patients thought to have BPH prior to starting therapy with silodosin to rule out the presence of carcinoma of the prostate. ( 5.6 ) Inform patients planning cataract surgery to notify their ophthalmologist that they are taking silodosin because of the possibility of Intraoperative Floppy Iris Syndrome (IFIS). ( 5.7 ) 5.1 Orthostatic Effects Postural hypotension, with or without symptoms (e.g., dizziness) may develop when beginning silodosin treatment. As with other alpha-blockers, there is potential for syncope. Patients should be cautioned about driving, operating machinery, or performing hazardous tasks when initiating therapy [see ADVERSE REACTIONS (6) , USE IN SPECIFIC POPULATIONS (8.5) , CLINICAL PHARMACOLOGY (12.2) , and PATIENT COUNSELING INFORMATION (17) ]. 5.2 Renal Impairment In a clinical pharmacology study, plasma concentrations (AUC and C max ) of silodosin were approximately three times higher in subjects with moderate renal impairment compared with subjects with normal renal function, while half-lives of silodosin doubled in duration. The dose of silodosin should be reduced to 4 mg in patients with moderate renal impairment. Exercise caution and monitor such patients for adverse events [see USE IN SPECIFIC POPULATIONS (8.6) and CLINICAL PHARMACOLOGY (12.3) ]. Silodosin is contraindicated in patients with severe renal impairment [see CONTRAINDICATIONS (4) ]. 5.3 Hepatic Impairment Silodosin has not been tested in patients with severe hepatic impairment, and therefore, should not be prescribed to such patients [see CONTRAINDICATIONS (4) , USE IN SPECIFIC POPULATIONS (8.7) and CLINICAL PHARMACOLOGY (12.3) ]. 5.4 Pharmacokinetic Drug-Drug Interactions In a drug interaction study, co-administration of a single 8 mg dose of silodosin with 400 mg ketoconazole, a strong CYP3A4 inhibitor, caused a 3.8-fold increase in maximum plasma silodosin concentrations and 3.2-fold increase in silodosin exposure (i.e., AUC). Concomitant use of ketoconazole or other strong CYP3A4 inhibitors (e.g., itraconazole, clarithromycin, ritonavir) is therefore contraindicated [see DRUG INTERACTIONS (7.1) ]. 5.5 Pharmacodynamic Drug-Drug Interactions The pharmacodynamic interactions between silodosin and other alpha-blockers have not been determined. However, interactions may be expected, and silodosin should not be used in combination with other alpha-blockers [see DRUG INTERACTIONS (7.3) ]. A specific pharmacodynamic interaction study between silodosin and antihypertensive agents has not been performed. However, patients in the Phase 3 clinical studies taking concomitant antihypertensive medications with silodosin did not experience a significant increase in the incidence of syncope, dizziness, or orthostasis. Nevertheless, exercise caution during concomitant use with antihypertensives and monitor patients for possible adverse events [see ADVERSE REACTIONS (6.1) and DRUG INTERACTIONS (7.6) ]. Caution is also advised when alpha-adrenergic blocking agents including silodosin are co-administered with PDE5 inhibitors. Alpha-adrenergic blockers and PDE5 inhibitors are both vasodilators that can lower blood pressure. Concomitant use of these two drug classes can potentially cause symptomatic hypotension [see DRUG INTERACTIONS (7.5) ]. 5.6 Carcinoma of the Prostate Carcinoma of the prostate and BPH cause many of the same symptoms. These two diseases frequently co-exist. Therefore, patients thought to have BPH should be examined prior to starting therapy with silodosin to rule out the presence of carcinoma of the prostate. 5.7 Intraoperative Floppy Iris Syndrome Intraoperative Floppy Iris Syndrome has been observed during cataract surgery in some patients on alpha-1 blockers or previously treated with alpha-1 blockers. This variant of small pupil syndrome is characterized by the combination of a flaccid iris that billows in response to intraoperative irrigation currents; progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs; and potential prolapse of the iris toward the phacoemulsification incisions. Patients planning cataract surgery should be told to inform their ophthalmologist that they are taking silodosin [see ADVERSE REACTIONS (6.1) ]. 5.8 Laboratory Test Interactions No laboratory test interactions were observed during clinical evaluations. Treatment with silodosin for up to 52 weeks had no significant effect on prostate-specific antigen (PSA).
6 ADVERSE REACTIONS Most common adverse reactions (incidence > 2%) are retrograde ejaculation, dizziness, diarrhea, orthostatic hypotension, headache, nasopharyngitis, and nasal congestion. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Aurobindo Pharma USA, Inc. at 1-866-850-2876 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. In U.S. clinical trials, 897 patients with BPH were exposed to 8 mg silodosin daily. This includes 486 patients exposed for 6 months and 168 patients exposed for 1 year. The population was 44 to 87 years of age, and predominantly Caucasian. Of these patients, 42.8% were 65 years of age or older and 10.7% were 75 years of age or older. In double-blind, placebo controlled, 12-week clinical trials, 466 patients were administered silodosin and 457 patients were administered placebo. At least one treatment-emergent adverse reaction was reported by 55.2% of silodosin treated patients (36.8% for placebo treated). The majority (72.1%) of adverse reactions for the silodosin treated patients (59.8% for placebo treated) were qualified by the investigator as mild. A total of 6.4% of silodosin treated patients (2.2% for placebo treated) discontinued therapy due to an adverse reaction (treatment-emergent), the most common reaction being retrograde ejaculation (2.8%) for silodosin treated patients. Retrograde ejaculation is reversible upon discontinuation of treatment. Adverse Reactions observed in at least 2% of patients: The incidence of treatment-emergent adverse reactions listed in the following table were derived from two 12-week, multicenter, double-blind, placebo-controlled clinical studies of silodosin 8 mg daily in BPH patients. Adverse reactions that occurred in at least 2% of patients treated with silodosin and more frequently than with placebo are shown in Table 1. Table 1 Adverse Reactions Occurring in ≥ 2% of Patients in 12-week, Placebo-Controlled Clinical Trials Adverse Reactions Silodosin N = 466 n (%) Placebo N = 457 n (%) Retrograde Ejaculation 131 (28.1) 4 (0.9) Dizziness 15 (3.2) 5 (1.1) Diarrhea 12 (2.6) 6 (1.3) Orthostatic Hypotension 12 (2.6) 7 (1.5) Headache 11 (2.4) 4 (0.9) Nasopharyngitis 11 (2.4) 10 (2.2) Nasal Congestion 10 (2.1) 1 (0.2) In the two 12-week, placebo-controlled clinical trials, the following adverse events were reported by between 1% and 2% of patients receiving silodosin and occurred more frequently than with placebo: insomnia, PSA increased, sinusitis, abdominal pain, asthenia, and rhinorrhea. One case of syncope in a patient taking prazosin concomitantly and one case of priapism were reported in the silodosin treatment group. In a 9-month open-label safety study of silodosin, one case of Intraoperative Floppy Iris Syndrome (IFIS) was reported. 6.2 Postmarketing Experience The following adverse reactions have been identified during post approval use of silodosin. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure: Skin and subcutaneous tissue disorders: toxic skin eruption, purpura, skin rash, pruritus, and urticaria Hepatobiliary disorders: jaundice, impaired hepatic function associated with increased transaminase values Immune system disorders: allergic-type reactions, not limited to skin reactions including swollen tongue and pharyngeal edema resulting in serious outcomes