Are you sure about that? I thought that certain drugs can cause gene mutations or permanently modify certain dna markers which can be passed on to offspring.
I tried the following on Google:
"genetic mutations caused by drugs"
"drug associated genetic mutations"
"drug induced genetic mutations"
The only result was The Wall Street Journal's War on Cancer, and Google picks up professional articles. You might find this article interesting, but no mention of drug associated genetic mutations, or similar phenomena, was made.