Characteristics of the study population at baseline

6A.1 Intention-to-treat population

6A.1.1 Baseline characteristics

As described in the previous chapter, the intention-to-treat population in the injectable heroin trial consisted of 174 subjects. The demographic background and other relevant baseline characteristics of these patients are displayed in Table 7.

Table 7. Characteristics intention-to-treat population at baseline (n = 174)

Sociodemographic background
The subjects in the intention-to-treat population (see Table 7) were predominantly male and from a Dutch/western background, with only few patients coming from a Surinamese (1.2%), Dutch Antillian (0.6%) or Moroccan (0.6%) background, no participants with a Turkish background, and 2.3% other(1) . The mean age in the sample amounted to 38.5 years (range: 27-52 years). The participants had typically received lower level education only, and were living alone.

Physical health
On the MAP-HSS, 65.5% had a score of 8 or higher, the inclusion-threshold used in the study for the area of physical health. The mean MAP-HSS score amounted to 11.5 (range: 0-31). Based on self-report, 13.3% had a positive HIV-status, and more than one-fifth currently received prescribed medication for a physical health problem. Subjectively, more than one-third of the participants reported to experience a (moderate, considerable or extreme) need for additional treatment in this domain.

Psychiatric status
SCL-90 total scores in the sample ranged from 2-331, with a mean of 74.3. Among the males and females, 58.7% and 64.5% reached the inclusion threshold score of 41 and 60, respectively. In the sample, 18.5% of the patients had at least once in their lives received inpatient treatment for a psychiatric problem. In addition, more than one-third had ever committed a suicide attempt, and one-third currently received prescribed medication for a psychiatric problem. DSM-IV mood and anxiety disorders were common on both lifetime and recent (i.e. past six months) basis. Lastly, almost one-third of the sample subjectively reported a (moderate, considerable or extreme) need for additional treatment for psychiatric problems.

Social functioning
Most subjects had been unemployed during the (three) years prior to the baseline interview, and currently received income primarily from public assistance or from illegal activities. Among those with financial debts (63.9%), the median debts amounted to EURO 2,950. In the month prior to the interview, 13.8% of the subjects had usually slept outside, in a public place or in a homeless shelter.
Among those who had ever (at least once) been charged for a crime against property, the number of charges ranged from 1 to more than 100, with a median of 15 charges (not in table). For those ever incarcerated, the years in detention ranged from 1 to more than 8 years, with a median of nearly 2 years (23 months). In the month prior to the interview, 58.1% had engaged in illegal activities to obtain money for 6 or more days, one of the inclusion thresholds in the social area. Lastly, almost half of the participants had had personal contact (of at least half an hour duration) less than 6 days in the previous month with a non-drug-using person (excluding treatment staff), the other inclusion threshold in the social area.

Substance use
In addition to heroin and methadone (both 100%), most participants had ever in their lives used cocaine (93.7%), large quantities of alcohol (i.e. at least five standard glasses a day) (74.0%), benzodiazepines (70.1%), and amphetamines (47.7%) on a regular (i.e. three or more days a week) basis. The mean number of years of regular heroin use amounted to 15.9 years. In addition, among those with "lifetime" regular cocaine use, cocaine had been used on a regular basis for 10.5 years. All participants were poly drug users. On the average, they had used more than one substance a day on a regular basis for 17.3 years.
All subjects had at least once in their lives been in outpatient substitution treatment (including the present methadone maintenance program they were recruited from), and had done so with a median of 2 times (i.e. two uninterrupted series of methadone maintenance treatment). On average, participants had used methadone on a regular basis for 12.1 years. In addition, more than half had ever participated in a detoxification program, and one-third in an inpatient drug-free program. Approximately one in twelve subjects had ever received treatment specifically for alcohol problems.
In the month preceding the baseline interview, all participants had used methadone, 98.9% heroin, and 90.2% cocaine. Among the cocaine users, both injecting (56.5%) and smoking (chasing/basing) (43.5%) were common routes of cocaine administration. Heroin and methadone had been used on a daily or nearly daily basis, and cocaine on slightly more than half the days (mean: 18.7 days). Subjects who had used illicit drugs in the previous month had spent an average of EURO 995 on drugs. Among the patients with considerable alcohol use, the money spent on alcohol amounted to an average of EURO 56. Lastly, almost two-thirds of the sample subjectively reported a (moderate, considerable or extreme) need for additional treatment for drug problems.

(1) To determine ethnicity, the definition of the Central Bureau of Statistics of the Netherlands (CBS, 1999) was used.