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The catechol-O-methyltransferase (COMT) enzyme catabolizes dopamine. The val(158)met single nucleotide polymorphism (rs4680) in the COMT gene has received considerable attention as a candidate gene for schizophrenia as well as for frontally mediated cognitive functions. Antisaccade performance is a good measure of frontal lobe integrity. Deficits on the task are considered a trait marker for schizophrenia. The aim of this study was to investigate the association of COMT val(158)met polymorphism with antisaccade eye movements in schizophrenia patients and healthy controls. Schizophrenia patients (N = 105) and healthy controls (N = 95) underwent infrared oculographic assessment of antisaccades. Subjects were genotyped for COMT val(158)met and divided into 3 groups according to genotype (val/val, val/met, and met/met). Patients displayed significantly more reflexive errors, longer and more variable latency, and lower amplitude gain than controls (all P < 0.02). A greater number of val(158) alleles was associated with shorter (P = 0.045) and less variable (P = 0.028) antisaccade latency and, nonsignificantly, with lower reflexive error rate (P = 0.056). None of these variables showed a group-by-genotype interaction (P > 0.1). There were no significant associations of genotype with measures of amplitude gain or spatial error (P > 0.2). The results suggest that COMT val(158) carrier status is associated with better performance on the antisaccade task. Possible explanations of this finding are discussed.

Objectives:Prescription rates of methylphenidate (MPH) are sharply rising in most Western countries. Although it has been reported that MPH has abuse potential, little is known about the prevalence of intravenous (IV) abuse of MPH. The aim of the study was to investigate the prevalence of IV MPH abuse among treatment-seeking IV substance abusers in Iceland.Methods:This is a descriptive population-based study using a semistructured interview assessing sociodemographics, substance abuse history, and the method of administration of 108 IV substance abusers. During 1 year, consecutively admitted adult inpatients with substance use disorder at any detoxification center in Iceland that reported any IV substance abuse in the past 30 days were invited to participate. Abuse was defined as nontherapeutic use of a substance to gain psychological or physiological effect.Results:Prevalence of any IV MPH abuse among participants was 88% in the last 30 days (95% confidence interval [CI], 0.82-0.94) and MPH was the most commonly abused substance (65%) and the preferred substance (63%). Around one third (30%) reported MPH as the first IV substance ever abused. However, among those reporting a shorter history than 10 years of IV abuse, 42% reported MPH as the first IV substance ever abused.Conclusions:This first nationwide study on IV abuse of MPH shows that it is common among treatment-seeking IV abusers in Iceland and suggests that MPH has high abuse potential. Therefore, both the use and possible abuse of MPH in those with high abuse potential should be monitored, especially in countries where MPH prescriptions rates are on the rise.

P e r f o r m a n c e o f P r o t h r o m b i n -P r o c o n v e r t i n T i m e a s a M o n i t o r i n g T e s t o f O r a l A n t i c o a g u l a t i o nT h e r a p y Oral anticoagulation therapy (OAT) with vitamin K antagonists (VKA) is most commonly monitored with the prothrombin clotting time (PT), which is sensitive to decreases in activity of any of the v i t a m i n K-dependent coagulation factors (F), II, VII, or X, as well as to decreases in fibrinogen or coagulation factor V (FV). 1 In the past, the PT was usually reported as a ratio of patient to control plasma clotting times (PT-ratio), but a system of international standardization was developed because of variability in clotting times obtained with different thromboplastins and variability in the methods of reporting the results. Accordingly, for the purpose of OAT control, PT results are now generally reported as international normalized ratios (INRs), 2 ' 3 ie, PT ratios are transformed to the ratio that would have been obtained if a standard reference thromboplastin preparation with an assigned international sensitivity index (ISI) of 1.0 had been used. 2,3When the PT is not done on fresh samples, a prolongation of the clotting time may occur from ex vivo factor V degradation (if plasma is stored at room temperature for more than 6 hours), whereas artifactual shortening may occur because of cold activation of FVII if plasma is stored at 4°C. 4 One way to circumvent these problems is to apply the prothrombin-proconvertin time (PP or P&P) on plasma kept at room temperature. The PP is a modified PT that is only sensitive to changes in FTJ, FVII, and FX because addition of adsorbed bovine plasma to the thromboplastin supplies the test mixture with optimal amounts of fibrinogen and FV for clot formation.5 When the PP is done on dilute patient plasma, it is also insensitive to direct anticoagulants, such as the lupus anticoagulant or heparin.6 ' 7 The PP results traditionally have been reported as the percentage of total coagulant activity of HI, FVII, and FX based on a dilution curve of normal plasma and not as clotting time ratios (or INR). This complicates the interpretation of anticoagulation intensity in relation to PT-based results and may be one reason for the decreasing use of the PP as a monitoring device. Also, although the PP is derived from the PT, clinical studies using the INR calculated directly from the PP are lacking. In clinical studies using the PP, conversions to INR have 672 Downloaded from https://academic.oup.