The following table is a compilation of every drug/substance that has at one time been controlled under the U.S. Federal Controlled Substances Act (CSA) and was then subsequently removed from control. Some of these, like naloxone, were scheduled on the basis of their chemistry alone (it's a derivative of Schedule II thebaine) and were decontrolled after HHS analysis showed they had no abuse potential. Others did not move from temporary to permanent scheduling because an HHS scientific evaluation failed to show abuse potential, leading to expiration of the temporary scheduling action. Oor, with MDMA, the drug was rescheduled after initial decontrol, despite a complex administrative law process.

A few were removed from control and then later controlled again, such as Fenfluramine, MDMA, and Butorphanol. This table is derived from the DEA's Chronology of Scheduling Actions: http://www.deadiversion.usdoj.gov/schedules/orangebook/b_sched_chron.pdf

Substance	Published	FR Citation	Effective	CSA Schedule
NALOXONE HCl	09-29-71	36 FR 19116	9-29-71	II -> 0
NALOXONE	12-24-74	39 FR 44392	12-24-74	II -> 0
NALTREXONE	03-06-75	40 FR 10455	3-6-75	II -> 0
APOMORPHINE	06-28-76	41 FR 26568	6-28-76	I -> 0
DEXTRORPHAN	10-01-76	41 FR 43401	10-1-76	II -> 0
NALBUPHINE	10-01-76	41 FR 43401	10-1-76	II -> 0
LOPERAMIDE	11-03-82	47 FR 49840	11-3-82	V -> 0
NALMEFENE	11-04-85	50 FR 45815	11-4-85	II -> 0
MDMA	01-27-88	53 FR 2225	1-27-88	I -> 0
But later...	02-22-88	53 FR 5156	3-23-88	back to I
PROPYLHEXEDRINE	12-03-91	56 FR 61372	12-3-91	V -> 0
FENFLURAMINE	05-06-97	--	--	IV -> 0
But later...	05-15-03	68FR26247	5-15-03	back to IV, withdrew the 1997 proposed rule
BUTORPHANOL (thebaine derived)	07-14-92	57FR31126	7-14-92	II -> 0
But later...	10-01-97	62FR51370	10-31-97	placed in IV
TFMPP	03-18-04	69 FR 12794	03-19-04	I --> 0
THENYLFENTANYL*	10-29-85	50FR43698	11-29-85 (expired 11-29-86)	I -> 0
BENZYLFENTANYL*	10-29-85	50FR43698	11-29-85 (expired 11-29-86)	I -> 0
BETA-HYDROXY-3-METHYL-FENTANYL**	11-26-86	51FR42834	11-29-86 (expired 5-29-87)	I -> 0
* : Temporarily Scheduled under 21 USC 811(h)
** : Extension of temporary control