I can only agree to what's been posted already and strongly argument against doing high dose olanzapine, or any antipsychotic for that matter. You'll get symptoms of dopamine antagonist overdose like akathisia (inability to sit or lay still, like drug induced restless legs, it's horrible trust me on this), fainting, anhedonia, cardiovascular disturbances etc
and possibly even anticholinergic symptoms, 100mg olanzapine is a HUGE dose, never heard of so much being prescribed.
What's good to counter opioid withdrawals is pregabalin or gabapentin, benzos or NMDA antagonists like memantine or your favorite dissociative RC. NMDAr antagonists greatly helped me to avoid opioid withdrawal more than once.
Or, when you're dealing with tramadol, then a S/NRI like fluoxetine can be of use since tramadol is a SNRI on top if it's opioid activity and thus comes with its own withdrawal. I failed to quit venlafaxine for a long time because of opioid like withdrawal and only made it by switching to fluoxetine.