Dutasteride is a synthetic 4-azasteroid compound that acts as a potent, selective, and irreversible inhibitor of both type I and type II 5α-reductase isoenzymes. It is used primarily for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to improve symptoms, reduce the risk of acute urinary retention, and reduce the need for BPH-related surgery. It is not indicated for use in women or children.
Adult: 0.5 mg orally once daily, with or without food. Must be taken consistently.
Note: Swallow the soft gelatin capsule whole. Do not crush, chew, or open the capsule. If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose. Do not double the dose. Can be taken at any time of day, but preferably at the same time each day.
Dutasteride inhibits the conversion of testosterone to the more potent androgen, dihydrotestosterone (DHT), by irreversibly binding to and inhibiting both type I and type II isoforms of the enzyme 5α-reductase. Type I isoenzyme is predominant in the skin, liver, and sebaceous glands, while type II is predominant in the prostate, seminal vesicles, epididymides, and hair follicles. By suppressing intraprostatic and serum DHT levels by >90%, it induces apoptosis of prostate epithelial cells, leading to a reduction in prostate gland volume.
Pregnancy: Pregnancy Category X. Contraindicated. Dutasteride is absorbed through the skin and can cause abnormalities of the external genitalia (hypospadias) in a male fetus if a pregnant woman is exposed. Women who are or may become pregnant must not handle crushed or broken capsules.
Driving: Patients should be cautioned about the potential for dizziness and somnolence, which may impair the ability to drive or operate machinery, particularly at the start of therapy or when combined with other medications (e.g., alpha-blockers).
| Tamsulosin, Alfuzosin, Silodosin (Alpha-1 blockers) | Increased risk of orthostatic hypotension, dizziness. Combination therapy (e.g., Dutasteride + Tamsulosin) is a common and approved regimen for BPH. | Moderate |
| Cimetidine | Cimetidine (a non-specific CYP inhibitor) may decrease the metabolism of dutasteride, potentially increasing its plasma concentration. Clinical significance is likely minimal due to wide therapeutic index. | Minor |
| Rifampicin, Carbamazepine, Phenytoin (Potent CYP3A4 Inducers) | May increase the metabolism of dutasteride, potentially reducing its plasma concentration and efficacy. | Moderate |
| Ketoconazole, Itraconazole, Ritonavir (Potent CYP3A4 Inhibitors) | May decrease the metabolism of dutasteride, potentially increasing its plasma concentration. Clinical significance is likely minimal. | Minor |
| Warfarin | No clinically significant interaction observed in studies. | None |