Table 1.

Demographic characteristics of the participants randomized to placebo, memantine 30mg, and memantine 60mg (N=81)^*

Characteristic	Placebo (n=27)	Memantine 30mg (n=27)	Memantine 60mg (n=27)	p-value
	mean (SD) or n (%)
Age (years)	40.5 (9.6)	41.5 (9.4)	42.0 (10.3)	0.86
Male (n)	20 (74.1)	24 (88.9)	22 (81.5)	0.37
Race/Ethnicity
Hispanic	6 (22.2)	10 (37.0)	8 (29.6)	0.41
Black	5 (18.5)	4 (14.8)	10 (37.0)
White	14 (51.9)	11 (40.7)	8 (29.6)
Other	2 (7.4)	2 (7.4)	1 (3.7)
Education (n)
Less than or equal to high school	12 (44.4)	10 (40.0)	14 (63.6)	0.53
Some college	9 (33.3)	8 (32.0)	5 (22.7)
College or more	6 (22.2)	7 (28.0)	3 (13.6)
Employment status
Full-time	8 (29.6)	9 (33.3)	5 (19.2)	0.15
Part-time	0 (0)	2 (7.4)	5 (19.2)
Unemployed/others	19 (70.4)	16 (59.3)	16 (61.5)
Currently married	4 (14.8)	2 (8.0)	4 (18.2)	0.63
Pattern of Opiate Use at baseline
Duration of use (yrs)	14.7 (10.5)	14.5 (11.2)	14.9 (11.5)	0.99
Amount of daily use (bags)**	8.3 (6.4)	6.4 (3.5)	7.2 (3.9)	0.46
Intravenous route	5 (18.5)	8 (29.6)	8 (29.6)	0.63
Prescription opiate users	2 (7.4)	4 (14.8)	2 (7.4)	0.57
Baseline Drug and Alcohol Use
Alcohol
Days used in last 30 days	1.0 (0–3.0)	1.0 (0–12.0)	1.0 (0–7.0)	0.59
Amount spent per day in last 30 days ($)	2.5 (1.8–3.5)	2.0 (1.0–3.3)	3.0 (1.8–4.0)	0.75
Marijuana
Days used in last 30 days	0.0 (0–1.25)	0.0 (0–0)	0.0 (0–2.0)	0.28
Amount/day in last 30 days (#joints)	1.0 (1.0–1.8)	1.0 (0)	1.0 (1.0–3.0)	0.43
Cocaine
Days used in last 30 days	1.0 (0–10.0)	0.0 (0–2.0)	0.0 (0–1.0)	0.24
Amount/day in last 30 days ($)	20 (10–21.3)	45 (18.8–50)	20 (10–43.8)	0.06

^*Frequencies may not sum to N=81 due to missing values. Percentages may not add up to 100 due to rounding.

^**One bag of heroin contains 50–100 mg of powder, which contains 50–70% of pure heroin.