Final answer:
Thalidomide is a drug that may cause malformations of the male external genitalia.
Step-by-step explanation:
Thalidomide is a drug that may cause malformations of the male external genitalia. It is classified as a teratogen, which are substances or conditions that cause deformities during embryogenesis and fetal development. Thalidomide's effects are based on its enantiomeric (chiral) structure, which can lead to severe side effects including testicular atrophy and prostate enlargement. Other drugs such as heroin, cocaine, and methamphetamine, as well as certain prescription medications, can also be considered teratogens.