PCV regiment and P-gp inhibitors

Inspired by Ben Williams who used Verapamil on BCNU and later on PCV regiment I was planning to use P-glycoprotein (P-gp) inhibitor like Verapamil during PCV chemotherapy.

Problem is that I can't find any research characterizing alkylating agents such as Carmustine, Procarbazine or Lomustine as P-gp substrates. Am I missing something?

Thank you.

Drugs to Combine with CCNU

My husband will soon begin CCNU for recurrence. In reviewing Ben Williams' document, I see that Verapamil and Calcium Channel Blockers like nimodipine have some evidence for augmentation benefit; however, the articles I found (both from his references and my own search) are quite old. Verapamil has more drug interactions than nimodipine. Is there any research about these drugs or other potential augmenters which I might share with his NO? (His NO has generally been supportive of repurposed drugs when I can share relevant studies. His NO does not want to combine CCNU with TMZ despite CeGaT study due to increased toxicity.)

Much gratitude and well wishes to all--
S.