dutasteride
Meaning of dutasteride: Prostate growth depends on a hormone built from testosterone, and this drug shuts down the enzyme that performs the conversion.
Definition of dutasteride
Dutasteride is a medication taken by mouth for the urinary symptoms of an enlarged prostate, a condition called benign prostatic hyperplasia. It is a 5-alpha reductase inhibitor: it blocks the enzyme that turns testosterone into dihydrotestosterone, the more potent androgen that drives prostate tissue to grow. With less of that hormone present, the gland slowly shrinks.
How does it work?
Testosterone itself does relatively little to the prostate. Inside the gland an enzyme called 5-alpha reductase converts it into dihydrotestosterone, a far stronger androgen, and that is the signal prostate tissue responds to. Dutasteride blocks the enzyme, so dihydrotestosterone levels in the blood and in the gland fall steeply. Deprived of the growth signal, the gland shrinks over months, which widens the channel the urethra runs through and eases hesitancy, a weak stream and night-time waking. Because the change depends on tissue slowly regressing rather than on a muscle relaxing, nothing happens quickly, and the effect reverses if the drug is stopped. That is why it is used as a 5-alpha reductase inhibitor for long-term control rather than for immediate relief.
How does it differ from finasteride?
| Dutasteride | Finasteride | |
|---|---|---|
| Enzyme forms blocked | Both type 1 and type 2 | Mainly type 2 |
| Effect on dihydrotestosterone | Near-complete suppression | Substantial but less complete |
| Time to clear the body | Months after the last dose | Days |
Both are used for benign prostatic hyperplasia, and either may be combined with a separate drug that relaxes the muscle in the bladder neck, since the two approaches work on different parts of the same problem.
What effects are known?
The recognized effects follow from lowering an androgen: reduced sexual desire, difficulty with erections, a smaller volume of ejaculate, and tenderness or enlargement of breast tissue. Some men report that sexual effects persist after stopping, and this remains debated. Lowering dihydrotestosterone also slows scalp hair loss, which is why related drugs are used for that purpose. The capsules are not handled by anyone who is or may become pregnant, because absorbed drug can interfere with development of the genitals in a male fetus, and blood donation is deferred for a period after the last dose for the same reason. The drug also lowers prostate-specific antigen, which matters when a prostate cancer screening result is interpreted.
Also known as
Used in a sentence
Dutasteride was prescribed to help reduce urinary symptoms related to an enlarged prostate.
Good to know
Dutasteride lowers prostate-specific antigen, a blood marker used in prostate cancer screening, so a PSA result from someone taking it is interpreted differently from one taken without it.