Sixty men were recruited from an inpatient psychiatric ward of Fatemieh hospital in Semnan after reviewing medical records. Subjects 18 to 60 years old were eligible if they met DSM-IV TR criteria according to the American Psychiatric Association guideline for current substance dependence as well as based on psychiatrist diagnosis. All patients had the history of regular Iranian crack usage at least within the last year. Patients with major psychological disorders, acute physical disorders, or brain organic disease were excluded from the study. Blood tests to rule out electrolytes and metabolic abnormalities included sodium (Na), potassium (K), blood sugar (BS), thyroid stimulating hormone (TSH), renal function tests (BUN and Cr), and liver function tests (AST, ALT, AlkPh, Bil) were done. All electrolytes were measured using biochemistry kit (Zistchimi, Iran), thyroid parameters were measured using Diaplus Kit (Diaplus, USA), serum bilirubin levels were measured using Parsazmoon biochemical kits (Iran), and other biomarkers were measured using Man kit (Man, Iran).
The study protocol and recruitment procedures were approved by the Review Board of the Semnan University of Medical Sciences. Written informed consent for the full protocol was obtained.
All subjects qualified by taking similar doses of clonidine (Tolidaroo, Iran; 0.2 mg/q8h at the first day, 0.3mg/q8h at the second day, 0.4 mg/q8h at the other days), Amitriptyline (Daroopakhsh, Iran; 75 mg on the first day, 100 mg on the second day, 150 mg on the third day, 200 mg on the fourth day and 300 mg on the other days), Ibuprofen (Tehranshimi, Iran; 800 mg/q6h), Hydroxyzine (Poorsina, Iran; 100 mg/q6h), Chlorpromazine (Tehranshimi, Iran; 100 mg/q6h), Hyoscine (Tehranshimi, Iran; 20 mg/q6h), and Lorazepam (Abidi, Iran; 2 mg/q6h).
The subjects were systematically randomized (EpiInfo program, WHO and CDC, Version 6.4) to receive either placebo (n = 30) or gabapentin (n = 30) for 7 days. Study investigators, raters, and subjects were also blinded to treatment assignment until all study visits were completed and the data set was cleared. Subjects were assessed at baseline, and on days 1, 2, 3, 4, 6, and 7.
During the double-blind phase, study medication was titrated to thirty capsules of either gabapentin (Irandaroo, Iran) or placebo orally 45 min prior to bedtime over a 7-day period. Each capsule received by the active medication group contained 300 mg of gabapentin (one capsule) for the first day and then 300 mg/q12h for the second day, 300 mg/q8h for the third day, and 600 mg/q8h for the other days. Each subject received one capsule at bedtime for three nights, then two capsules at bedtime for four nights. On day 7, subjects were reassessed by the study physician.
Subjective Opioid Withdrawal Scale (SOWS) was measured as a self-administered scale for grading opioid withdrawal symptoms. This scale assesses the intensity of 16 symptoms which is rated by patients on a scale of 0 (not at all) to 4 (extremely). Among all components, we used the item of body pain for assessing the severity of pain in both the gabapentin and placebo groups (11
Data are expressed as mean ± standard deviation (SD) for quantitative variables and were summarized by absolute frequencies and percentages for categorical variables. Continuous variables were compared using t-test or non-parametric Mann-Whitney U-test whenever the data did not appear to have normal distribution or when the assumption of equal variances was violated across the groups. Categorical variables across the two groups were compared using the chi-square test or Fisher>s exact test if required. We considered 2-tailed p-values of ≤ 0.05 as statistically significant. Analyses were performed using SPSS statistical software (version 16.0) for windows.