5Α-Reductase Inhibitors

Products

5α-Reductase inhibitors are commercially available in many countries in the form of film-coated tablets and capsules. Finasteride was the first agent from this group to be approved in 1993 (USA: 1992). There are two finasteride drugs on the market. One with 5 mg for the treatment of prostate enlargement (Proscar, generic) and one with 1 mg for the treatment of androgenic alopecia in men (Propecia, generic). Dutasteride was released in 2003 (Avodart, generic).

Structure and properties

The 5α-reductase inhibitors are structurally related to testosterone.

Effects

5α-Reductase inhibitors (ATC G04CB) are effective against symptoms of prostate enlargement, reduce prostate size, and stabilize hair loss in androgenetic alopecia. The effects are based on inhibition of the intracellularly localized enzyme 5α-reductase, which is responsible for the synthesis of 5α-dihydrotestosterone (DHT) from testosterone. DHT plays a role in the development of both prostate enlargement and androgenetic hair loss.

Indications

  • Benign prostate enlargement in men
  • Hereditary hair loss in males (androgenetic alopecia).

There are other indications for which there is no official approval.

Dosage

According to the professional information. The drugs are taken once daily and always at the same time of day.

Active ingredients

Not commercially available in many countries:

Contraindications

  • Hypersensitivity
  • Use in women, children and adolescents
  • Pregnancy

During pregnancy, contact with the drugs must be avoided! The full precautions can be found in the drug leaflet.

Interactions

Finasteride and dutasteride are substrates of CYP3A4 and corresponding interactions are possible.

Adverse effects

The most common possible adverse effects include:

  • Decreased libido
  • Impotence, erectile dysfunction
  • Ejaculation disorders
  • Sensitivity to the touch of the breast, breast enlargement (gynecomastia).