Finasteride and Dutasteride are inhibitors of 5-alpha-reductase that is used for the treatment of benign prostatic hypertrophy in men and some forms of alopecia. A pregnant woman exposed to dutasteride or finasteride may absorb enough to cause a male fetus to develop abnormal external genitalia.


Mechanism of teratogenic effect: The drug suppresses dihydrotestosterone levels in the fetus. This can cause improper development in the external genitalia of a male fetus. The effect would depend on the dose, duration of exposure and the gestational age of the fetus.


Types of exposure:

(1) dermal, from handling capsules, especially if broken

(2) oral ingestion

(3) blood transfusion (from a blood donor who has taken the drug within the past 6 months)


Possible effects on a newborn infant:

(1) abnormal external genitalia in a male fetus, with feminization

(2) reduction in adrenal gland weight

(3) reduction in prostate weight

(4) increase in ovarian weight in females or testis weight in males


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