If you want to nod off then use opiates
is not heroin
If you want the kratom to hit stronger then take more, or use really strong enhanced kratom like UEI.
But why would you want to abuse it so badly?
Kratom has a lot to offer a lot of people. If it is killing your pain then its doing its job. Abusing it will only add to the increasing likelihood that it will end up banned like so many other valuable substances have been.
Kratom is illegal in country's all over the world now, for various reasons, but one thing that is guaranteed to make law makers reconsider its status is how much potential for abuse it has.
Posts like this worry me and many others who don't want to see people who need it legitimately lose it because someone wants to nod off on it.
There are threads on how to potentiate kratom, try using the search engine.