Heroin addiction is a chronic complex disease with a substantial genetic contribution. This study was designed to identify genetic variants that are associated with susceptibility to develop heroin addiction by analyzing 1350 variants in 130 candidate genes. All subjects had Caucasian ancestry. The sample consisted of 412 former severe heroin addicts in methadone treatment, and 184 healthy controls with no history of drug abuse. Nine variants, in six genes, showed the lowest nominal P values in the association tests (P < 0.01). These variants were in noncoding regions of the genes encoding the mu (OPRM1; rs510769 and rs3778151), kappa (OPRK1; rs6473797) and delta (OPRD1; rs2236861, rs2236857 and rs3766951) opioid receptors; the neuropeptide galanin (GAL; rs694066); the serotonin receptor subtype 3B (HTR3B; rs3758987) and the casein kinase 1 isoform epsilon (CSNK1E; rs1534891). Several haplotypes and multilocus genotype patterns showed nominally significant associations (e.g. OPRM1; P 5 0.0006 and CSNK1E; P 5 0.0007). Analysis of a combined effect of OPRM1 and OPRD1 showed that rs510769 and rs2236861 increase the risk of heroin addiction (P 5 0.0005). None of these associations remained significant after adjustment for multiple testing. This study suggests the involvement of several genes and variants in heroin addiction, which is worthy of future study. Heroin addiction is a chronic relapsing disease characterized by compulsive drug seeking, drug abuse, tolerance and physical dependence. It is treated by methadone, buprenorphine and behavioral therapy. Heroin addiction is part of group of addictions (e.g. cocaine, alcohol and nicotine) that constitute a worldwide public health crisis. The genetic contribution to vulnerability to develop heroin addiction is 40-60%, suggesting a complex inheritance mode in which multiple genes exert a small effect, along with the environment (Kendler et al. 2003;Tsuang et al. 1996Tsuang et al. , 1998. ). These include variants in the genes encoding the mu and kappa opioid receptors, dopamine receptors D2 and D4, serotonin receptor 1B, gamma-aminobutryic acid (GABA) receptor subunit gamma 2, catechol-O-methyltransferase, period circadian protein (PER3), proenkephalin, proopiomelanocortin, tryptophan hydroxylase 2 and brain-derived neurotrophic factor.To identify genetic variants that underlie heroin addiction, we performed a candidate gene case-control association study using a single nucleotide polymorphism (SNP) array that was designed by the group of D. Goldman at the National Institute of Alcohol Abuse and Alcoholism (NIAAA). This approach is based on physiological hypotheses and the genes were selected based on their function (e.g. drug receptors, neurotransmitters, transporters and drug metabolism enzymes) and related pathways (e.g. reward modulation, behavioral control, cognitive function, signal transduction and stress response). In order to maximize the power of the study, the cases were selected from the extreme margin of the specific phenotype range (e.g. severe heroin a...

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Methadone is a mu-opioid receptor agonist used for treating opiate dependence. The range of effective methadone doses is broad. Part of the large inter-individual variability in efficacy may be accounted for by genetic factors. Methadone is a substrate of the transporter P-glycoprotein (P-gp) 170 that is encoded by the ABCB1 (MDR1) gene. Thus, P-gp variants may play a role in methadone absorption and distribution. We assessed the association between ABCB1 polymorphisms and methadone dose requirements in 98 methadone-maintained patients. The stabilizing methadone doses were normally distributed with a mean and median dose of 160 mg/day (range 30-280 mg/day). Statistical analysis showed significant difference in genotype frequencies between the 'higher' (>150 mg/day) and 'lower' (< or =150 mg/day) methadone dose groups for single nucleotide polymorphism (SNP) 1236C>T (rs1128503) (experiment-wise P = 0.0325). Furthermore, individuals bearing the 3-locus genotype pattern TT-TT-TT (rs1045642, rs2032582 and rs1128503) have an approximately 5-fold chance of requiring the 'higher' methadone dose, while individuals heterozygous for these three SNPs have an approximately 3-fold chance of stabilizing at the 'lower' methadone dose (point-wise P-value = 0.026). These data suggest that specific ABCB1 variants may have clinical relevance by influencing the methadone dose required to prevent withdrawal symptoms and relapse in this population.

Heroin addiction is a chronic complex disease with a substantial genetic contribution. This study was designed to identify gene variants associated with heroin addiction in African Americans. The emphasis was on genes involved in reward modulation, behavioral control, cognitive function, signal transduction and stress response. We have performed a case-control association analysis by screening with 1350 variants of 130 genes. The sample consisted of 202 former severe heroin addicts in methadone treatment and 167 healthy controls with no history of drug abuse. Single nucleotide polymorphism (SNP), haplotype and multi-SNP genotype pattern analyses were performed. Seventeen SNPs showed point-wise significant association with heroin addiction (nominal P < 0.01). These SNPs are from genes encoding several receptors: adrenergic (ADRA1A), arginine vasopressin (AVPR1A), cholinergic (CHRM2), dopamine (DRD1), GABA-A (GABRB3), glutamate (GRIN2A) and serotonin (HTR3A) as well as alcohol dehydrogenase (ADH7), glutamic acid decarboxylase (GAD1 and GAD2), the nucleoside transporter (SLC29A1) and diazepambinding inhibitor (DBI). The most significant result of the analyses was obtained for the GRIN2A haplotype G-A-T (rs4587976-rs1071502-rs1366076) with protective effect (P uncorrected = 9.6E-05, P corrected = 0.058). This study corroborates several reported associations with alcohol and drug addiction as well as other related disorders and extends the list of variants that may affect the development of heroin addiction. Further studies will be necessary to replicate these associations and to elucidate the roles of these variants in drug addiction vulnerability.

The aim of this study is to characterize patients with chronic pain in methadone maintenance treatment (MMT). Between September and December, 2003, 170 consecutive patients from an MMT clinic participated in a questionnaire survey on pain (duration and severity). Chronic pain was defined as current pain lasting for >or=6 months. The patients' maintenance methadone dosage and urine tests for drug abuse during the month before and of the survey were recorded. Of the 170 patients, 94 (55.3%) experienced chronic pain. They had a significantly higher proportion of chronic illness (74.5%) compared to non-pain patients (44.7%) (Fisher's Exact Test P<0.0005). Twelve (12.8%) of the chronic pain patients scored their pain as mild, 38 (40.4%) as moderate, 22 (23.4%) as severe and 22 (23.4%) as very severe. Pain duration significantly correlated with pain severity (Pearson R=0.3, P>0.0005) and was significantly associated with methadone daily dosage: patients with pain duration of >or=10 years (n=26) were receiving the highest methadone dosage (182.1+/-59.2 mg/day), those with pain duration from 1 to 10 years (n=59) 160.9+/-56.2 mg/day, and those with pain duration of <1 year (n=9) 134.2+/-73.2 mg/day. Patients in the non-pain group (n=76) were receiving 147.1+/-52.8 mg/day of methadone (ANOVA, F=3.1, P=0.03). We conclude that pain duration and severity significantly correlated. Although methadone was not prescribed for the treatment of pain but rather for opiate addiction, the patients in the MMT clinic with prolonged pain were prescribed a significantly higher methadone dosage compared to patients with short pain duration, and non-pain patients.