To describe smoking over the course of the study period, the adjusted number of CPD was determined in weekly intervals. The adjusted selleck chemical Wortmannin CPD was derived by taking the number of days smoked in the past 30 days and multiplying it by the number of cigarettes per day; this product was then divided by 30 to arrive at the adjusted CPD. Statistical Analyses The sample of participants with follow-up ASIs for whom longitudinal smoking data were available (n = 124) was used to characterize the prevalence and severity of smoking in this population of opioid-dependent pregnant women seeking treatment, as well as for comparisons of the smoking profiles between the two treatment conditions. Data were analyzed using independent samples t tests for continuous data and chi-square tests for categorical variables.

A longitudinal linear mixed effects model with a random intercept (Dupont & Plummer, 1990; Henderson, Diggle, & Dobson, 2000), which controlled for study site, was used to examine changes in number of CPD by treatment condition. The model that was fit as follows: y ij= �� 0 + �� 0i + (�� 1) time + �� 2 treatment + �� 3 time * treatment + e ij, where y ij is the adjusted CPD for the ith person at the jth timepoint. This model does not require that all individuals start at the same point in their pregnancy and does not model the change from baseline explicitly. In the context of this study, relying on change from baseline would be inappropriate as participants entered the study at different points in their pregnancies, resulting in CPD being measured at different points in their pregnancies.

Instead, the model uses all available data to estimate an ��average�� rate of change per week in adjusted CPD for each treatment condition (buprenorphine and methadone). This model, thus, enables calculation of a difference in expected rate of change between the two treatment groups, which is the coefficient for the interaction between time and treatment (�� 3). Figure 1 shows the fitted trajectories (estimated slopes or changes over time) for each treatment condition. Figure 1. Cigarette smoking by treatment condition during study period. Based on the formulae of Dupont and Plummer (1990), 67 methadone participants and 57 buprenorphine participants would yield 80% power to detect a (moderate) effect size of 0.

51 or greater, where effect size is calculated as the difference in means of the two groups divided by the pooled standard error. All analyses were performed in STATA v. 11.0. RESULTS Participant Characteristics The overall sample characteristics are shown in Table 1. The sample Entinostat was mostly White, unemployed, and unmarried with a mean (SD) age of 26.4 (5.4) years old. Participants entered the study shortly after the start of the second trimester on average. The characteristics of those randomized to methadone (n = 67) and buprenorphine (n = 57) are also shown in Table 1.