Effects of levodopa-carbidopa-entacapone and smoked cocaine on facial affect recognition in cocaine smokers

Abstract

In addition to difficulties in daily social functioning, regular cocaine users have decrements in social processing (the cognitive and affective processes underlying social behavior) relative to non-users. Little is known, however, about the effects of clinically-relevant pharmacological agents, such as cocaine and potential treatment medications, on social processing in cocaine users. Such drug effects could potentially alleviate or compound baseline social processing decrements in cocaine abusers. Here, we assessed the individual and combined effects of smoked cocaine and a potential treatment medication, levodopa-carbidopa-entacapone (LCE), on facial emotion recognition in cocaine smokers. Healthy non-treatment-seeking cocaine smokers (N = 14; two female) completed this 11-day inpatient within-subjects study. Participants received LCE (titrated to 400mg/100mg/200mg b.i.d.) for five days with the remaining time on placebo. The order of medication administration was counterbalanced. Facial emotion recognition was measured twice during target LCE dosing and twice on placebo: once without cocaine and once after repeated cocaine doses. LCE increased the response threshold for identification of facial fear, biasing responses away from fear identification. Cocaine had no effect on facial emotion recognition. Results highlight the possibility for candidate pharmacotherapies to have unintended impacts on social processing in cocaine users, potentially exacerbating already existing difficulties in this population.

Keywords: Facial emotion recognition; cocaine; dopamine; levodopa; social processing.

Figure 1

Top Panel. Effects of LCE (Levodopa/Carbidopa/Entacapone 400 mg/100 mg/200 mg BID) and cocaine (6, 12, 25, 50, 50 mg before testing) on response bias, assessed with β. Data are means (±SEM). There was a main effect of LCE on β values for facial fear recognition, such that values on LCE were higher than those on placebo. Higher β values indicate an increased threshold for identifying faces as fearful (i.e. more ‘no’ responses). LCE = Levodopa/Carbidopa/Entacapone; PBO = placebo LCE treatment; Baseline = Testing without cocaine administration; Post Cocaine = Testing after acute cocaine administration; asterisk denotes significant difference from placebo (p < 0.05). Bottom Panel. Effects of LCE and cocaine on sensitivity to emotional faces, assessed with d’. Sensitivity varied between emotion types, with d’ higher for happy than all other emotional categories, higher for fear and angry than neutral and sad faces, and higher for sad than neutral faces. There were no effects of LCE or cocaine on sensitivity to facial emotions.

Figure 2

Ratings of “Good Drug Effect” during cocaine administration sessions as a function of time (collapsed across placebo and LCE cocaine administration sessions). Placebo cocaine was administered at 0 minutes. Active cocaine doses (6, 12, 25, 50, 50 mg in ascending order) were administered at 14, 28, 42, 56, and 70 minutes. The facial emotion recognition task was started at 80 minutes. BL = baseline. Data are means (±SEM). Asterisks denote significant difference from baseline (p < 0.05).