Silodosin is metabolised mainly by cytochrome P450 3A4 (CYP3A4), UDP-glucuronosyltransferases (UGTs), alcohol dehydrogenase (ADH), and aldehyde dehydrogenase (ALDH).
Co-administration with potent inhibitors of CYP3A4 activity blocks the metabolism of silodosin. This may result in elevated plasma drug concentrations.
Silodosin (Urief®) should be administered with care when co-administered with the following drugs.
| Drugs | Signs, Symptoms, and Treatment |
Mechanism and Risk Factors |
| Hypotensive agents | Since orthostatic hypotension may occur, attention should be paid to dosage reduction, etc. | Patients receiving treatment with a hypotensive agent may have diminished ability to regulate blood pressure on standing. |
| Azole anti-fungal agents Itraconazole, etc. | Elevated plasma concetrations of silodosin have been reported following coadministration with ketoconazole ( oral preparation not marketed in Japan), a potent CYP3A4 inhibitor. Since elevated plasma concentrations of silodosin may occur following coadministration with azole antifungal agents, attention should be paid to dosage reduction, etc. |
Since azole antifungal agents inhibit CYP3A4, elevated plasma concentrations of silodosin may occur following coadministration with these preparations. |
| Phosphodiesterase-5 inhibitors Sildenafil citrate, Vardenafil hydrochloride hydrate etc. |
It has been reported that symptomatic hypotension may occur in concomitant use of these drugs. | Since silodosin has an α-blocking effect, co-administration may enhance the hypotensive effect due to the vasodilatory effect of these drugs. |
