Table 1.

Characteristics of Included Studies

Author	Country	Study Design	Condition	N	Gender	Age	Criteria
Younger 200917	USA	Placebo-controlled, single-blind, crossover, pilot study	Fibromyalgia	10	Female	22–55	ACR 1990
Ramanathan 201218	USA	Case report	Fibromyalgia	1	Male	37	ACR 1990
Younger 201319	USA	Randomized placebo-controlled crossover double-blind study	Fibromyalgia	31	Female	23–65	ACR 1990
Parkitny 201720	USA	Single-blind, crossover study	Fibromyalgia	8	Female	31–63	ACR 2010
Metyas 201821	USA	Two small prospective pilot open label studies	Fibromyalgia	25	24 Female +1male	30–75	ACR 1990
Oaks 201822	USA	Case series	Opioid-Induced Hyperalgesia and Fibromyalgia	254(217 OIH & 37 FM)	152 Female & 102 Male	14–89	ACR 1990
Bruun-Plesner 202023	Denmark	Prospective dose–response study	Fibromyalgia	25	Female	27–59	ACR 1990 and ACR 2011
Jackson 202124	USA	Case series	Opioid Induced Hyperalgesia and Fibromyalgia	76(55 OIH, and 21 FM)	19 Female +2 Male	37–50	ACR 1990
Siembida 202216	USA	Case report	Depression in Fibromyalgia	1	Male	60	ACR 1990

Note: ACR, American College of Rheumatology; OIH, opioid-induced hyperalgesia; FM, fibromyalgia.