As posted on VIP board:

Didrex (Benzphetamine) and Bontril (phendimetrazine) are Schedule III under federal law, unlike phentermine which is Schedule IV. Cosidering the similarity in effect, one wonders why, but nobody ever said the law had to be logical or based on sound science. I think the didrex "shortage" is just the result of physicians working for "soft" (questionarre only) OP's trying to stay out of trouble by sticking with the lower scheduled drugs (e.g, phentermine; tenuate). Assuming you have medical records to document obesity, I would expect you would have no trouble finding an OP to prescribe the meds following phone consultation and submission of records--same procedure as hydrocodone or other Shedule III drugs. Hope this helps.