Table 5.

Clinical characteristics of studies reviewed

Ref	Recruitment route	MAT Status	Abstinence duration prior to study	Duration of heroin use/dependence
Langleben et al. [46]	MMT clinic in USA	MMT	16 ± 13 months	n.r.
		54 ± 33 months
Mei et al. [52]	Inpatient DTX clinic in China	DTX (scanned prior to TX or >8 h after first BUP dose)	50 ± 24 h	4.5 ± 4.4 years
Li et al. [49]	Residential treatment in China	AB, no MAT	21.7 ± 16 days	78.6 ± 50.1 months
Lou et al. [51]	Forced DTX center in China	DTX	STA: 1.2 ± 0.1 months	STA: 7.0 ± 1.0years
			LTA: 13.6 ± 0.4 months	LTA: 8.2 ± 1.1 years
Li et al. [50]	Drug rehab center in China	AB (post-methadone-assisted DTX)	STA: 23.6 ± 17.6 days	STA: 80.5 ± 54.4 months
			LTA:193.3 ± 42.7 days	LTA: 96.3 ± 69.5 months
Langleben et al. [47]	Court mandated OUD TX (selected XRNTX) in USA	AB	97 ± 123 days	12.5 ± 8 years
Wang et al. [45]	MMT in China	MMT Group A: <1 year; 7.92 ± 2.89 months	n.r	Group A: 48.6 ± 4 9.9 months
		Group B: >2 years; 29.62 ± 3.53 months		Group B: 49.64 ± 42.5 months
Li et al. [48]	MMT clinic in China	MMT	n.r.	Relapsers: 69.2 ± 68.5 months
		Relapsers: 18.3 ± 11.5 months		Non-relapsers: 92.3 ± 70.5 months
		Non-relapsers: 25.5 ± 17.3 months
Walter et al. [43]	Centre of Substance Use Disorders in Switzerland	HMT	n/a	21.1 ± 5.7 years
		7.3 ± 4.4 years
Wang et al. [44]	Local ads in China	Active users prior to enrollment, DTX as part of study	n/a	n.r.
Gradin et al. [57]	NHS addiction service in UK	MMT > 6 weeks at stable dose	n.r.	3 year minimum
Yip et al. [58]	RCT of cocaine use disorder treatment in USA MMT clinic	MMT > 2 months at stable dose	n.r.	n.r.
Wang et al. [63]	Forced DTX program in China (2–5 months post-DTX)	AB	3.4 ± 0.9 months	6.9 ± 2.9 years
Schmidt et al. [64, 65]	Centre of Substance Use Disorders in Switzerland	HMT > 6 months (>3 months at stable dose)	n/a	21 ± 6.4 years
Fu et al. [69]	Inpatient abstinence treatment in China	AB, no MAT	7.64 ± 2.16 weeks	6.25 ± 3.53 years
Schmidt et al. [70]	Centre of Substance Use Disorders in Switzerland	HMT > 6 months (>3 months at stable dose)	n/a	20.54 ± 6. 56 years
Yucel et al. [71]	Community treatment providers in Australia	MMT & BMT	24 h minimum	107.44 ± 60.87 months
		31.54 ± 32.55 months
Wang et al. [74]	Individuals seeking DTX in China	Active users prior to enrollment	5.1 ± 0.29 h	19.9 ± 3.1 years
Jiang et al. [80]	Individuals seeking treatment in China	MMT	n.r.	10.83 ± 4.61 years
		6-7 days
Liu et al. [83]	MMT clinic in China	MMT	4.76 ± 0.7 months	85.3 ± 46.2 months
		Duration n.r.
Xie et al. [76]	Hospital in China	AB	8.05 ± 2.51 weeks	6.59 ± 3.72 years
Jiang et al. [79]	Hospital in China	MMTa	6–7 days	9.21 ± 5.28 years
		Duration n.r.
		2 participants not on MMTa
Wang et al. [75]	MMT clinic in China	AB	n.r.	81.5 ± 33.9 months
Xie et al. [77]	Hospital in China	AB	8.05 ± 2.51 weeks	6.59 ± 3.72 years
Li et al. [82]	MMT clinic in China	MMT > 3 months at stable dose	n.r.	n.r.
Schmidt et al. [85]	Centre of Substance Use Disorders in Switzerland	HMT > 6 months (>3 months at stable dose)	n/a	21.5 ± 6.10 years
Zhang et al. [78]	Forced DTX program in China	AB	8.05 ± 2.51 weeks	6.2 ± 3.53 years
Chang et al. [72]	MMT clinic in China	MMT > 3 months	n.r.	Non-relapsers: 275.7 ± 69.1 months
				Relapsers: 224 ± 64.5 months
Li et al. [81]	n.r.	AB	21.7 ± 16 days	78.6 ± 50.1 months
Qiu et al. [84]	Hospital in China	UROD + NMT	n.r.	4.96 ± 1.97 years
Wang et al. [73]	n.r.	MMT > 3 months	237 ± 424.35 days	7.66 ± 3.55 years

Ref. reference, MMT methadone maintenance treatment, USA United States of America, n.r. not reported, DTX detox, TX treatment, BUP buprenorphine, AB abstinent, MAT medication-assisted therapy, STA short-term heroin abstinence, LTA long-term heroin abstinence, OUD opioid use disorder, XRNTX extended release naltrexone, HMT heroin maintenance treatment, n/a not applicable, NHS National Health Service, UK United Kingdom, RCT randomized controlled trial, BMT buprenorphine maintenance treatment, UROD general anesthesia, NMT naltrexone maintenance treatment