Does anyone know how long the drug companies have known their medicine are harmful to babies?

I do not have much information on this medicine recall, but I will be looking into it. My question at this point is how long have the companies known? I had a child that died in 1993 the day he took Dimetap. They tested the Dimetap at the time to make sure it wasn't tainted and such, mainly to find out why my baby died. It was determined SIDS. I am just wondering if this could something to look into?