Felicione 2019.

Study characteristics
Methods	Design: Double‐blind RCT Recruitment: People who smoke were recruited from an outpatient opioid‐maintenance clinic in West Virginia, USA Setting: Outpatient opioid‐maintenance clinic in West Virginia, USA Study start date/Study end date: Not reported
Participants	Total N: 25; N per arm: Placebo (non‐nicotine): 11; Active (18 mg/ml nicotine): 14 Inclusion criteria: ≥18 years of age Report smoking ≥10 cpd for ≥ one year Report a current interest in quitting smoking Exclusion criteria: Reported regular use of any nicotine/tobacco product other than cigarettes, including EC, or were already engaged in attempts to quit smoking Inclusion based on specific population characteristic: People who smoke who were currently receiving a buprenorphine/naloxone combination in sublingual form, and had maintained sobriety from opioids and all other illicit substances for at least 90 consecutive days as verified via urinalysis 73.0% women; mean age 32.5; mean cpd 22; mean FTND 5.8 Motivated to quit: Quit ladder Score (range 1 ‐ 10): 5.6 average
Interventions	EC: Refillable Compared nicotine (18 mg/ml) to non‐nicotine EC. Second‐generation EC consisted of the eGo‐T battery (900mAh, 3.3 V constant output) (Joyetech; Irvine, CA) and the Kanger mini Protank‐II, 1.5 ml Pyrex glass tank with a drip tip and atomizer head coils (KangerTech; China), choice between tobacco (n = 15) and menthol (n = 10) flavored liquid (2‐week supply). Participants were then trained in EC device operation, including assembly, liquid filling, manual battery operation, and cleaning/storage. Practised puffing on EC in the presence of a team member, and asked questions if needed. Participants instructed to use their ECIG ad libitum every day for 2 weeks
Outcomes	Baseline (day 1), 14 days, 28 days for clinic measures. Data also collected via text‐messages over 2‐week intervention period Withdrawal/side effects: Every evening during the 2‐week intervention period, participants rated a variety of effects possibly experienced as a result of nicotine/tobacco withdrawal and/or use of the ECIG: nausea, dizziness, throat irritation/soreness, cough, dry mouth, headache, shortness of breath, irritability/frustration/anger, craving/urge to smoke, and other. Each item was rated on a continuous scale that ranged from 0 (not at all) to 100 (extremely) Expired air CO Other outcomes: Self‐reported cigarette and EC use; readiness to quit at day 1, 14 and 28
Study funding	Not reported
Author declarations	Not reported
Notes	New for 2020 update
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “Using a mixed factorial, simple randomization, double‐blind study design, participants were assigned to one of two ECIG conditions…” (No further details given)
Allocation concealment (selection bias)	Unclear risk	No details on allocation given.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: “double‐blind study design”, no further detail given
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: “double‐blind study design”, no further details given.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: “…80.6% completed the two‐week intervention (n=14 active; n=11 placebo), and 70.9% also completed the follow‐up session (n=13 active; n=9 placebo).” Active follow‐up completion rate: 13/14 = 93%; Placebo follow‐up completion rate: 9/11= 82% N.B. 6 participants were disqualified post‐randomization: Quote: “Of those individuals who were screened for the study, 93.9% were enrolled (n = 18 active; n = 13 placebo); two individuals who were ineligible provided an expired air CO level < 10 ppm. Six of the enrolled participants (n = 4 active and n = 2 placebo; n = 5 tobacco flavor and n = 1 menthol flavor) were disqualified for responding to 7 or fewer days of text messages.”
Selective reporting (reporting bias)	Unclear risk	All measures listed were reported: Self‐reported cigarette use, text message‐based cigarette use, e‐cig use, expired air CO, readiness to quit ladder, withdrawal/side effect; No study protocol or clinical trial record available to confirm all intended outcome measures were reported