Dutasteride

What it is

Dutasteride is a 5-alpha-reductase inhibitor that blocks both forms of the enzyme converting testosterone into dihydrotestosterone. The resulting fall in DHT reduces prostate volume and slows androgen-driven hair loss. It is used for benign prostatic enlargement and for male pattern hair loss.

Used for

• Prostate
• Hair loss

What to know while taking it

Food does not matter for absorption, and the drug clears from the body slowly, so effects and side effects alike fade only gradually after it is stopped. It roughly halves the PSA result, so a doctor reading a prostate blood test must know it is being taken, or a genuine rise can be hidden. Testosterone rises slightly as DHT is suppressed, but it stays within the normal range and calls for no action. Capsules must not be handled by a pregnant woman because of the risk to a male fetus; blood donation is also avoided while taking it and for a period afterwards.

When to see a doctor

Falling libido, erectile problems, low mood, or breast tenderness, swelling or a lump should be discussed with a doctor rather than managed alone. New or worsening urinary symptoms, or a PSA reading interpreted without knowledge of this drug, are also reasons to see a doctor.

Worth knowing

• Halves the PSA result
• Pregnant women must not handle it
• Can lower libido

Markers to watch

• Testosterone