Hi: severe burning and itching with scabs and dandruff on scalp: clinic prescribed Bactrim Sulfameth/Tmp oral for infection but anything OTC for head?

Just a. thought but you should consider seeing a Dermatologist...what you have sounds like it may be more "serious" than Dandruff..eg PSORIASIS,,,suggest you try an anti-Psoriasis SHAMPOO ..ask your Pharmacist for recommendation....

Hope this is helpful
Dr Z.