Flowrap® (Silodosin), a selective alpha-1 adrenergic receptor antagonist, is indicated for the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH). Flowrap® (Silodosin) is not indicated for the treatment of hypertension.

The recommended dose is Silodosin 8 mg capsule orally once daily with a meal.

Renal impairment: Silodosin is contraindicated in patients with severe renal impairment (CCr < 30 mL/min). In patients with moderate renal impairment (CCr 30–50 mL/min), the dose should be reduced to Silodosin 4 mg once daily, taken with a meal. No dosage adjustment is needed in patients with mild renal impairment (CCr 50–80 mL/min).

Hepatic impairment: Silodosin has not been studied in patients with severe hepatic impairment (Child-Pugh score ≥ 10) and is therefore contraindicated in these patients. No dosage adjustment is needed in patients with mild or moderate hepatic impairment.

Silodosin capsules are contraindicated in patients with severe renal impairment (CCr < 30 mL/min), severe hepatic impairment (Child-Pugh score ≥ 10), concomitant administration with strong Cytochrome P450 3A4 (CYP3A4) inhibitors (e.g., ketoconazole, clarithromycin, itraconazole, ritonavir), and in patients with a history of hypersensitivity to Silodosin.

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.

Renal impairment: In a clinical pharmacology study, plasma concentrations (AUC and Cmax) of Silodosin were approximately three times higher in subjects with moderate renal impairment compared with those 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.

Hepatic impairment: Silodosin has not been tested in patients with severe hepatic impairment and therefore should not be prescribed to such patients.

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 a 3.2-fold increase in Silodosin exposure (AUC). Concomitant use of ketoconazole or other strong CYP3A4 inhibitors (e.g., itraconazole, clarithromycin, ritonavir) is therefore contraindicated.

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. A specific pharmacodynamic interaction study between Silodosin and antihypertensive agents has not been performed. However, in Phase 3 clinical studies, patients 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.

Carcinoma of the prostate: Carcinoma of the prostate and BPH cause many of the same symptoms and frequently co-exist. Therefore, patients thought to have BPH should be examined prior to starting therapy with Silodosin to rule out prostate carcinoma.

Intraoperative floppy iris syndrome: This condition has been observed during cataract surgery in some patients on alpha-1 blockers or those previously treated with alpha-1 blockers. Patients planning cataract surgery should inform their ophthalmologist that they are taking Silodosin.

Pregnancy: Category B. Silodosin is not indicated for use in women.

Pediatric use: Silodosin is not indicated for use in pediatric patients. Safety and effectiveness in pediatric patients have not been established.
Geriatric use: In double-blind, placebo-controlled, 12-week clinical studies of Silodosin, orthostatic hypotension was reported in:

2.3% of Silodosin patients < 65 years (1.2% for placebo),
2.9% of Silodosin patients > 65 years (1.9% for placebo),
5.0% of Silodosin patients > 75 years (0% for placebo).

Otherwise, no significant differences in safety or effectiveness were observed between older and younger patients.

CYP3A4 inhibitors: Concomitant administration with strong inhibitors (e.g., ketoconazole, clarithromycin) is contraindicated. Use caution with moderate inhibitors (e.g., diltiazem, erythromycin, verapamil).

P-glycoprotein inhibitors: Silodosin is not recommended in patients taking strong P-gp inhibitors such as cyclosporine.

Alpha-blockers: Silodosin should not be used in combination with other alpha-blockers.
Digoxin: Co-administration did not significantly alter digoxin pharmacokinetics; no dose adjustment is required.
PDE5 inhibitors: Combined use may increase the risk of symptomatic hypotension.

Silodosin should be taken with a meal to reduce the risk of adverse events, as food affects its absorption.

Common: Retrograde ejaculation (2.8%), dizziness, diarrhea, nasal congestion.
Uncommon: Insomnia, increased PSA, sinusitis, abdominal pain, asthenia, rhinorrhea.

Postmarketing: Skin rash, pruritus, urticaria, jaundice, allergic reactions, pharyngeal edema.

In case of overdose, monitor blood pressure and heart rate. Maintain the patient in a supine position, administer intravenous fluids if needed, and consider vasopressors if necessary. Dialysis is unlikely to be effective due to Silodosin's high protein binding.

Store at a temperature not exceeding 30°C in a dry place. Protect from light and moisture.

Warning: Keep out of reach of children.