Dr. Drew -- Still On Call for "Celebrity Rehab"

Dr. Drew Pinsky hasn't permanently checked out of "Celebrity Rehab" -- the show is currently on hold ... but TMZ has learned, VH1 is keeping Drew on deck for a possible reboot.

As we first reported -- VH1 is taking a break from "Celebrity Rehab" while producers ponder a new show centered around struggling celebrity couples. In the meantime, Dr. Drew is busy with two other TV shows -- a daytime program on CW and another show on HLN.

Howard Lapides -- Dr. Drew's longtime manager and producing partner -- tells us, Drew's exit from "Rehab" is merely a "timing issue."