Products
Dutasteride is commercially available in capsule form (Avodart). It is also available in combination with the alpha blocker tamsulosin (Duodart); see dutasteride tamsulosin. The active ingredient has been approved in many countries since 2003. Generics were registered in 2017. Generic versions of Duodart were approved in 2018.
Structure and properties
Dutasteride (C27H30F6N2O2, Mr = 528.5 g/mol) is a 4-azasteroid and structurally closely related to finasteride, the first agent from this group also commercially available in the indication of prostate enlargement. Dutasteride exists as a white to slightly yellow powder that is insoluble in water.
Effects
Dutasteride (ATC G04CB02) is a selective, potent, and competitive inhibitor of 5alpha-reductase, which converts testosterone to 5α-dihydrotestosterone. 5α-Dihydrotestosterone represents an important growth stimulus for prostate enlargement. Unlike finasteride, dutasteride inhibits not only type 2 but also type 1 5alpha-reductase and is a more potent inhibitor of the enzyme with a slow dissociation. Both isoforms are overexpressed in the prostate. Dutasteride is therefore also called a dual inhibitor. It has a long half-life of 3-5 weeks. It reduces prostate size, relieves symptoms, and improves urinary flow.
Indications
Dutasteride is approved alone or in combination with tamsulosin for the treatment and prevention of progression of benign prostate enlargement. Like finasteride, it is indicated for the treatment of androgenetic alopecia (inherited hair loss) in men, according to a 2010 phase III study, but it has not yet been approved for this indication. Dutasteride may also prevent prostate cancer, according to a large study, but it also has not yet been approved in this indication.
Dosage
According to the SmPC. The capsules are usually taken once daily, independent of meals.
Contraindications
- Hypersensitivity
- Women
- Children and teenagers
Full precautions can be found in the drug label. Women in pregnancy should not come into contact with the drug, as it may be harmful to fertility. Furthermore, it must be noted that dutasteride leads to a strong decrease in PSA.
Interactions
Dutasteride is metabolized via CYP3A4. Interactions with CYP3A4 inhibitors or inducers are possible. No interactions are known with tamsulosin.
Adverse effects
The most common adverse effects include sexual dysfunction such as impotence, decrease in libido, ejaculatory dysfunction, and gynecomastia, which is an enlargement of the male mammary gland. Allergic reactions may occur. More side effects can be expected with combination with tamsulosin than with monotherapy.
