Silodosin

What it is and how it works

Mechanism of Action Silodosin is a selective antagonist of post-synaptic alpha-1 adrenoreceptors, which are located in the human prostate, bladder base, bladder neck, prostatic capsule, and prostatic urethra. Blockade of these alpha-1 adrenoreceptors can cause smooth muscle in these tissues to relax, resulting in an improvement in urine flow and a reduction in BPH symptoms. An in vitro study examining binding affinity of silodosin to the three subtypes of the alpha-1 adrenoreceptors (alpha-1A, alpha-1B, and alpha-1D) was conducted. The results of the study demonstrated that silodosin binds with high affinity to the alpha-1A subtype.

Mechanism class: Adrenergic alpha-Antagonists

Indications

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

Dosage and administration (summary)

8 mg capsules taken orally once daily with a meal. 4 mg capsules taken orally once daily with a meal for those with moderate renal impairment [Creatinine Clearance (CCr) 30 mL/min to 50 mL/min]. Dosing Information The recommended dose is 8 mg orally once daily with a meal. Patients who have difficulty swallowing pills and capsules may carefully open the silodosin capsule and sprinkle the powder inside on a tablespoonful of applesauce. The applesauce should be swallowed immediately (within 5 minutes) without chewing and followed with an 8 oz glass of cool water to ensure complete swallowing of the powder.

Contraindications

Patients with severe renal impairment [Creatinine Clearance (CCr < 30 mL/min)]. Patients with severe hepatic impairment (Child-Pugh score ≥ 10). Concomitant administration with strong Cytochrome P450 3A4 (CYP3A4) inhibitors (e.g., ketoconazole, clarithromycin, itraconazole, ritonavir). Patients with a history of hypersensitivity to silodosin or any of the ingredients of silodosin capsules.

Warnings and precautions

Postural hypotension, with or without symptoms (e.g., dizziness), may develop when beginning silodosin treatment. In patients with moderate renal impairment, silodosin dose should be reduced to 4 mg once daily. Silodosin should not be used in combination with other alpha-blockers. Examine patients thought to have BPH prior to starting therapy with silodosin to rule out the presence of carcinoma of the prostate. Inform patients planning cataract surgery to notify their ophthalmologist that they are taking silodosin because of the possibility of Intraoperative Floppy Iris Syndrome (IFIS).

Pregnancy

Pregnancy Risk Summary Silodosin is not indicated for use in females.

Storage and supply

White, opaque, hard gelatin 8 mg capsules . Cap is imprinted with "LU" in green. Body is imprinted with "Q72" in green. 8 mg capsules are supplied in HDPE bottles of: 30 capsules (NDC 68180-741-06) 90 capsules (NDC 68180-741-09) Bottles of 30 and 90 capsules are supplied with child-resistant closures. White, opaque, hard gelatin 4 mg capsules.

Source: Silodosin (Silodosin) — US FDA prescribing information, 2025-10-07, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.