@mantis,
There is no safe or proven drug that will lead to getting twins as Kodak has put it.
As a matter of fact,getting of twins is much more of genetical (genes) than those backstreet drugs.
The genetical lineage flows from one generation to another and you cannot influence this.
Influence to get twins through drugs can lead to malformation of your child (s)........to some extent where drugs are used and can lead to twins,the danger would be to give birth to foetuses with non formed or incomplete limbs.......and several deformities.
Please stay safe and dont try this (drugs).
Disclaimer : This is my opinion and not a recommendation.
"You're not supposed to be so blind with patriotism that you can't face reality. Wrong is wrong, no matter who says it". Malcolm X