Hold on your on clozapine 400mg if i was you id strongly not take dxm. Sorry im not trying to be a bummer but i believe clozapine at that dose is a last line for people with schizophrenia because it may be slightly more potent but may have slightly more side effects.
Idk if you have schizophrenia or not and im not trying to judge. I have to get my blood monitored due to needing multiple mood stabilizers.
But, im just trying to stress this im not antidrugs, i even just took my nicotine, amphetamine, and caffeine as soon as i got up and took dxm almost every day years (didnt end well dont recommend) if i was in your shoes or you where my brother asking me i would strongly suggest you not take dxm period due to:
Clozapine having a relately high side effect profile some of which can be life threatening. So mixing drugs with it can be super dangerous.
Given the dose your on i assume you might have schizophrenia
Given your on a drug typically used when others dont work i am guessing you have (like me no judgement just concerned) a serious mental illness
Lastly, due to the state of the world the last thing id want is to have a psychotic episode or whatever and be hospitalized during covid 19 not even just getting ill but idk it might be chaos i could guess it might take forever to process you ect.
(Sorry for the length too much coffee) please be safe.