@merpreb
Hi Merry,
For example linear drugs, if you increase your dose by 100mg the amount of medication in your blood (therapeutic level) will increase proportionately to your regular and/or increased dose.

In a non-linear drug like Neurontin, Dilantin, Tegratol all seizure meds since that’s what I’m most familiar with. If you increase the dose amount of medication in your blood (therapeutic level) can actually increase or decrease. For example, when I was taking Dilantin the therapeutic level is 10-20 yet regardless of my dose my therapeutic level would either be toxic (usually above 30) or below 10. I had to switch my medication because the doctor regardless what he did could not get the Dilantin to stabilize between 10-20. Non linear meds need watched closely.
That is a simplistic overview but it’s much more involved than that. Many more factors are involved.
Jake