Methadone dose in heroin-dependent patients: role of clinical factors, comedications, genetic polymorphisms and enzyme activity

Relationship between ABCB1 polymorphisms and serum methadone concentration in patients undergoing methadone maintenance therapy (MMT)

BACKGROUND

Methadone is a substrate of the permeability glycoprotein (P-gp) efflux transporter, which is encoded by the ABCB1 (MDR1) gene. Large interindividual variability in serum methadone levels for therapeutic response has been reported. Genetic variations in ABCB1 gene may be responsible for the variability in observed methadone concentrations.

OBJECTIVE

This study investigated the associations of ABCB1 polymorphisms and serum methadone concentration over the 24-hour dosing interval in opioid-dependent patients on methadone maintenance therapy (MMT).

METHODS

One hundred and forty-eight male opioid-dependent patients receiving MMT were recruited. Genomic deoxyribonucleic acid (DNA) was extracted from whole blood and genotyped for ABCB1 polymorphisms [i.e. 1236C>T (dbSNP rs1128503), 2677G>T/A (dbSNP rs2032582), and 3435C>T (dbSNP rs1045642)] using the allelic discrimination real-time polymerase chain reaction (PCR). Blood samples were collected at 0, 0.5, 1, 2, 4, 8, 12, and 24 hours after the dose. Serum methadone concentrations were measured using the Methadone ELISA Kit.

RESULTS

Our results revealed an association of CGC/TTT diplotype (1236C>T, 2677G>T/A, and 3435C>T) with dose-adjusted serum methadone concentration over the 24-hour dosing interval. Patients with CGC/TTT diplotype had 32.9% higher dose-adjusted serum methadone concentration over the 24-hour dosing interval when compared with those without the diplotype [mean (SD) = 8.12 (0.84) and 6.11 (0.41) ng ml^-1 mg^-1, respectively; p = 0.033].

CONCLUSION

There was an association between the CGC/TTT diplotype of ABCB1 polymorphisms and serum methadone concentration over the 24-hour dosing interval among patients on MMT. Genotyping of ABCB1 among opioid-dependent patients on MMT may help individualize and optimize methadone substitution treatment.

Risk factors for weight gain during methadone maintenance treatment

BACKGROUND

Weight gain was reported during methadone maintenance treatment (MMT). However, its relation to eating habits and specific risk factors, including methadone dose or serum level, was limited. The aims of this study were to characterize risk factors for weight gain and to study current eating habits, food preferences, and nutrition knowledge.

METHODS

Patients with available measures of weight and height (body mass index [BMI]) at admission to MMT and at follow-up, when methadone serum levels were determined (after 1 year or when stabilized) (N = 114), were studied (using the Addiction Severity Index [ASI], drugs in urine, methadone doses, and serum levels). In addition, 109 current patients with available earlier (5.8 ± 2.6 years earlier) BMI completed eating behavior rating and nutrition knowledge questionnaires, and their current and earlier BMI were compared.

RESULTS

The BMI of 114 newly admitted patients increased from 22.5 ± 3.8 to 24.4 ± 4.3 (P < .0005). Once stabilized on methadone, BMI increased further (24.3 ± 4.5 to 25.6 ± 5.0; P < .0005; n = 74), with no change in methadone doses (125.6 ± 32.5 to 128.0 ± 34.1; F = 1.4, P = .2) or serum levels (495.6 ± 263.7 to 539.8 ± 306.2; F = 1.3, P = .2). Repeated-measures analyses revealed that BMI elevation was higher among 45 hepatitis C virus seronegative and 46 non-benzodiazepine-abusing on-admission patients. Those who scored lower on knowledge about healthy diet and showed a higher sweet-foods preference had a higher BMI.

CONCLUSION

BMI increased over time, but independent of methadone dosage and blood levels. As expected, worse diet habits and a desire for sweet foods are related to higher BMI. Paradoxically, healthier status (i.e., hepatitis C seronegative, no benzodiazepine abuse) at admission is predictive of greater weight gain during MMT. Education about nutrition habits is recommended.

Variability of response to methadone: genome-wide DNA methylation analysis in two independent cohorts

Aim: Methadone maintenance treatment is characterized by large interindividual dose variability. The aim of this study was to evaluate whether DNA methylations are associated with daily dose of methadone. Materials & methods: Subjects stabilized at high (n = 12) or low (n = 12) methadone doses were selected from two independent cohorts (French and Swiss). DNA methylation patterns were analyzed using HumanMethylation450 BeadChips. Results: In total, 584 differentially methylated sites were identified in the French cohort corresponding to 352 genes. Of these, 26 were replicated in the Swiss cohort. The methylation status of 13 genes varied similarly in both cohorts and calcium signaling pathway was significantly enriched. Conclusion: Our results indicate that differentially methylated sites are associated with methadone daily dose and give insights into the molecular pathways underlying this interindividual dose variability.

La méthadone à l’heure de la médecine personnalisée : prédiction de la dose efficace ? Prédiction des effets secondaires ?

Rationnel

La méthadone est prescrite comme traitement de substitution de la dépendance aux opiaces depuis les années 1960 . Néanmoins, l’expérience des cliniciens montre que la réponse thérapeutique est obtenue à des doses extrêmement variables d’un patient à l’autre et qu’il est également difficile de prédire les effets secondaires.

Méthode

En collaboration avec plusieurs centres de soins d’Île-de-France (CSAPA Espace Murger, AP–HP, hôpital Fernand-Widal, Dr Gaël Dupuy ; clinique Liberté, hôpital Paul-Guiraud, Dr Didier Touzeau ; CSAPA Moreau de Tours, centre hospitalier Sainte-Anne, Dr Xavier Laqueille ; CSAPA Monte Cristo, AP–HP, HEGP, Dr Cyrille Orizet ; CSAPA EGO, association Aurore, Dr Philippe Coeuru ; ECIMUD, AP–HP, hôpital Louis-Mourier, Dr Anne-Marie Simonpoli ; CSAPA 110 Les Halles, PSA 75, Dr Pierrre Polomeni ; Bus Méthadone Gaia, Dr Elisabeth Avril) nous avons conduit une étude recueillant des données cliniques et génétiques chez des patients héroïnomanes stabilisés sous traitement par méthadone.

Résultats

Deux cent seize patients ont été inclus entre 2008 et 2013. Nous présenterons ici des résultats concernant la prédiction des doses nécessaires à l’équilibre thérapeutique chez 80 patients ayant complété une hospitalisation de jour comprenant une exploration fonctionnelle du métabolisme hépatique . Nous présenterons également des résultats sur 161 patients ayant bénéficié d’une mesure de l’espace Qt par un cardiologue et du recueil de facteurs de risque cliniques et génétiques de Torsades de pointes, complétant des données préliminaires que nous avons publié . Ces résultats permettront de discuter les données à recueillir pour une prescription optimisée de méthadone à l’heure de la médecine personnalisée.