Influence of EPHX1 c.337 T>C and UGT2B7*2 genetic polymorphisms on the requirement of carbamazepine maintenance dose in person with epilepsy (PWE) of Southern part of India: a cross-sectional genetic association study

OBJECTIVES

Carbamazepine (CBZ) is a first-line antiseizure drug used for focal onset seizures. It exhibits inter-individual variability in plasma carbamazepine levels and there are both genetic and non-genetic factors having a role in the requirement of CBZ maintenance dose. The aim was to study the influence of EPHX1 c.337 T>C and UGT2B7*2 genetic polymorphisms on CBZ maintenance dose requirement in persons with epilepsy.

METHODS

Persons with epilepsy (PWE) of both gender of age 15-65 years on carbamazepine monotherapy who had been taking same maintenance dose for one year were eligible. Five milliliter of venous blood was collected in 10% EDTA under aseptic precautions. After centrifugation, the cellular component was used for DNA extraction and genotyping. For three genotypes of EPHX1 c.337 T>C and UGT2B7*2, the differences in mean carbamazepine dose were analyzed using Analysis of Variance (ANOVA). An unpaired t-test was used to draw a comparison between the genotypes and CBZ maintenance dose requirement for dominant and recessive models of EPHX1 c.337 T>C and UGT2B7*2. A value of p<0.05 was considered to be statistically significant.

RESULTS

For UGT2B7*2 (rs 7439366), CT required a higher dose (CT 626 mg/day and TT 523 mg/day) but not found to be significant (p-value 0.167). PWE carrying CT genotype of EPHX1 c.337 T>C had 62 mg higher dose when compared to homozygous mutant CC (590 mg/day for CT and 528 mg/day for CC) but p-value was not found to be significant (p-value 0.835).

CONCLUSIONS

The results of our study done in 115 PWE showed there was a lack of association between SNPs of EPHX1 c.337 T>C, UGT2B7*2 and CBZ maintenance dose requirement in Southern part of India and this finding has to be confirmed in a larger sample size.

Efficacy and safety of food allergy oral immunotherapy in adults

BACKGROUND

Oral immunotherapy (OIT) is an emerging method for treating food allergy in children. However, data regarding adults undergoing this process are lacking.

METHODS

We retrospectively analyzed the medical records of patients with food allergy aged ≥17 years who completed OIT treatment between April 2010 and December 2020 at Shamir Medical Center. Data were compared with that of children aged 4 to <11 years and adolescents aged ≥11 to 17 treated during the same time period.

RESULTS

A total of 96 adults at a median age of 22.3 years who underwent OIT for milk (n = 53), peanut (n = 18), sesame (n = 7), egg (n = 5), and tree nuts (n = 13) were analyzed and compared with 1299 children and 309 adolescents. Adults experienced more adverse reactions requiring injectable epinephrine, both during in-clinic up-dosing (49% vs. 15.9% and 26.5% for children and adolescents, respectively, p < 0.0001) and during home treatment (22.9% vs. 12.4%, p = 0.007 for children, and 17.5%, p = 0.23 for adolescents). Most adults (61.5%) were fully desensitized, but the rates of full desensitization were significantly lower than children (73.4%, p = 0.013). Significantly more adults (28.3%) undergoing milk OIT failed treatment than children (14.3%, p = 0.015) and adolescents (14.1%, p = 0.022), while failure rates in adults undergoing OIT for other foods were low (9.3%) and comparable with children and adolescents.

CONCLUSIONS

OIT is successful in desensitizing most adults with IgE-mediated food allergy. Adults undergoing milk OIT are at increased risk for severe reactions and for OIT failure while failure rates in adults undergoing OIT for other foods are low.

Maintenance Dose in Long-Term Antipsychotic Treatment: 2022

The act of discontinuing the antipsychotic medication may be directly associated with relapse. This relationship might be due to adaptations that continue to exist after treatment is stopped, such as dopaminergic hypersensitivity. Therefore, more progressive weaning off antipsychotic medication may help reduce the likelihood of relapse when the medication is stopped. As there is a need to gradually reduce or stop using antipsychotic medication, our team tried to conduct a more in-depth search to give further answers to the suggested recommendations. Around 192 articles were gathered for our research, but we could only narrow our search to 36, which were further filtered, and eight were used. We went through all of the pertinent information available until May 2022 and reviewed it to determine the risks associated with prolonged antipsychotic usage and abrupt cessation in the psychotic spectrum of diseases. PubMed, Google Scholar, and Psychiatry Online were the databases used, and the keywords that were looked for and utilized were antipsychotics, tapering, relapse, maintenance dosage, schizophrenia, and psychosis. The recurrence incidence was high in patients in whom antipsychotics were stopped and in whom the dosage was quickly lowered. Patients who were gradually weaned off their antipsychotic medication and kept on the lowest effective dose had a much lower risk of experiencing a relapse. We suggest more studies, including randomized clinical trials and monitoring, considering the enhancement of guidelines for the total cessation of antipsychotic medication use.

Impact of VKORC1, CYP2C9, CYP1A2, UGT1A1, and GGCX polymorphisms on warfarin maintenance dose: Exploring a new algorithm in South Chinese patients accept mechanical heart valve replacement

BACKGROUND

Warfarin is the most recommended oral anticoagulant after artificial mechanical valve replacement therapy. However, the narrow therapeutic window and varying safety and efficacy in individuals make dose determination difficult. It may cause adverse events such as hemorrhage or thromboembolism. Therefore, advanced algorithms are urgently required for the use of warfarin.

OBJECTIVE

To establish a warfarin dose model for patients after prosthetic mechanical valve replacement in southern China in combination with clinical and genetic variables, and to improve the accuracy and ideal prediction percentage of the model.

METHODS

Clinical data of 476 patients were tracked and recorded in detail. The gene polymorphisms of VKORC1 (rs9923231, rs9934438, rs7196161, and rs7294), CYP2C9 (rs1057910), CYP1A2 (rs2069514), GGCX (rs699664), and UGT1A1 (rs887829) were determined using Sanger sequencing. Multiple linear regressions were used to analyze the gene polymorphisms and the contribution of clinical data variables; the variables that caused multicollinearity were screened stepwise and excluded to establish an algorithm model for predicting the daily maintenance dose of warfarin. The ideal predicted percentage was used to test clinical effectiveness.

RESULTS

A total of 395 patients were included. Univariate linear regression analysis suggested that CYP1A2 (rs2069514) and UGT1A1 (rs887829) were not associated with the daily maintenance dose of warfarin. The new algorithm model established based on multiple linear regression was as follows: Y = 1.081 - 0.011 (age) + 1.532 (body surface area)-0.807 (rs9923231 AA) + 1.788 (rs9923231 GG) + 0.530 (rs1057910 AA)-1.061 (rs1057910 AG)-0.321 (rs699664 AA). The model accounted for 61.7% of individualized medication differences, with an ideal prediction percentage of 69%.

CONCLUSION

GGCX (rs699664) may be a potential predictor of warfarin dose, and our newly established model is expected to guide the individualized use of warfarin in clinical practice in southern China.

Phase 2, randomized multi oral immunotherapy with omalizumab 'real life' study

BACKGROUND

Oral immunotherapy (OIT) is frequently discontinued due to adverse events (AEs) and current data suggests that lowering OIT doses can minimize severity and frequency of AEs. However, the minimum daily dose that can enable desensitization and induce immune responses in multi-food OIT (mOIT) is unknown.

METHODS

Participants aged 2-25 years with multi-food allergies were pretreated with fixed-dose omalizumab (150 mg, 3 doses, every 4 weeks), and randomized 1:1 to receive mOIT to a total maintenance dose of either 300 or 1200 mg total protein, (total dose includes at least two and up to a max of five allergens) and then transitioned to real-food protein equivalents after 18 weeks of treatment. The primary endpoint was the proportion of subjects with increases in IgG4/IgE ratio of at least 2 allergens by ≥25% from baseline after 18 weeks of therapy. The primary efficacy and safety analyses were done in the intention-to-treat population.

RESULTS

Sixty participants were enrolled across two sites. Seventy percent of participants in both arms showed changes in sIgG4/sIgE ratio in at least 2 allergens with no difference between the treatment groups (OR [95% CI] = 1.00 [0.29, 3.49]). Overall, there were no differences in AEs between the 300 and 1200 mg groups (19% vs. 17%, p = .69), respectively.

CONCLUSIONS

Our data suggest that plasma marker changes are induced early, even at a total protein dose of 300 mg inclusive of multiple allergens when mOIT is combined with fixed-dose omalizumab. Identification of optimal mOIT dosing with adjunct omalizumab is needed for the long-term success of OIT.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT03181009).

Impact of the CYP2D6 Genotype on Metoprolol Tolerance and Adverse Events in Elderly Chinese Patients With Cardiovascular Diseases

The latest consensus has changed CYP2D6 genotyping among Chinese population, while its impact on metoprolol tolerance and adverse events in elderly Chinese patients with cardiovascular diseases remains unclear. In this study, we prospectively included elderly patients who started metoprolol treatment for cardiovascular indications. According to the latest consensus on CYP2D6 genotype-to-phenotype translation, the patients were categorized as normal, intermediate, or poor metabolizers (NMs, IMs, or PMs, respectively) by detecting the presence of the CYP2D6*1, *2, *5, *10, and *14. Logistic regression model was used to analyze the correlation between the CYP2D6 phenotype and incidence of adverse events, which were assessed over a 12-week period. In this study, there were 651 (62.7%) NMs, 385 (37.1%) IMs, and 3 (0.3%) PMs. After 12 weeks of follow-up, compared with NMs, IMs had the lower maintenance dose [50.0 (25.0–50.0) mg/day vs. 25.0 (25.0–50.0) mg/day, p < 0.001] and lower weight-adjusted maintenance doses (0.52 ± 0.25 mg/day/kg vs. 0.42 ± 0.22 mg/day/kg, p < 0.001), and had higher incidence of postural hypotension (6.0% vs. 10.9%, p = 0.006), bradycardia (21.5% vs. 28.6%, p = 0.011), asystole (0.8% vs. 3.1%, p = 0.009) and syncope (2.0% vs. 6.2%, p = 0.001). In logistic regression model, the overall incidence of adverse events was 1.37-fold larger in IMs than in NMs (odds ratio = 1.37, 95% confidence interval = 1.05–1.79, p = 0.021). We conclude that IMs have lower tolerance and higher incidence of metoprolol-related adverse events than NMs in elderly Chinese patients with cardiovascular diseases. CYP2D6 genotyping is justifiable in elderly patients to minimize the risk of adverse events and ensure the benefits of metoprolol.

Factors Affecting Voriconazole Trough Concentration and Optimal Maintenance Voriconazole Dose in Chinese Children

Voriconazole is a triazole antifungal agent commonly used for the treatment and prevention of invasive aspergillosis (IA). However, the study of voriconazole's use in children is limited. The present study was performed to explore maintenance dose to optimize voriconazole dosage in children and the factors affecting voriconazole trough concentration. This is a non-interventional retrospective clinical study conducted from 1 January 2016 to 31 December 2020. The study finally included 94 children with 145 voriconazole trough concentrations. The probability of achieving a targeted concentration of 1.0–5.5 µg/mL with empiric dosing increased from 43 (45.3%) to 78 (53.8%) after the TDM-guided adjustment. To achieve targeted concentration, the overall target maintenance dose for the age group of less than 2, 2 to 6, 6 to 12, and 12 to 18 years old was approximately 5.71, 6.67, 5.08 and 3.31 mg·kg−1/12 h, respectively (p < 0.001). Final multivariate analysis found that weight (p = 0.019), dose before sampling (p < 0.001), direct bilirubin (p < 0.001), urea nitrogen (p = 0.038) and phenotypes of CYP2C19 were influencing factors of voriconazole trough concentration. These factors can explain 36.2% of the variability in voriconazole trough concentration. Conclusion: In pediatric patients, voriconazole maintenance doses under the target concentration tend to be lower than the drug label recommended, but this still needs to be further studied. Age, body weight, dose, direct bilirubin, urea nitrogen and phenotypes of CYP2C19 were found to be influencing factors of voriconazole concentration in Chinese children. The influence of these factors should be taken into consideration during voriconazole use.

Experience of perampanel monotherapy beyond initial titration to achieve seizure freedom in patients with focal-onset seizures with newly diagnosed or currently untreated recurrent epilepsy: A post hoc analysis of the open-label Study 342 (FREEDOM)

Objective

This post hoc analysis evaluated whether continued treatment with perampanel monotherapy beyond initial titration may be appropriate for patients with focal‐onset seizures (FOS) with currently untreated epilepsy to achieve seizure freedom with an effective dose.

Methods

Study 342 (NCT03201900; FREEDOM) is a single‐arm, open‐label, Phase III study of perampanel monotherapy. Patients aged ≥12 years with untreated FOS received perampanel 4 mg/d in a 32‐week Treatment Phase (6‐week Titration and 26‐week Maintenance Periods); in case of seizure(s) during Maintenance Period, patients could enter a 30‐week Treatment Phase (4‐week Titration and 26‐week Maintenance Periods) to be up‐titrated to perampanel 8 mg/d. The primary endpoint was seizure‐freedom rate during Maintenance Period in the modified Intent‐to‐Treat (mITT) Analysis Set (patients who had ≥1 post‐dose efficacy measurement during Maintenance Period); safety was monitored. This analysis of 4‐mg/d efficacy data assessed the proportion of patients achieving seizure freedom during the Maintenance Period (responders) relative to patients with an early/later response (depending on seizure status during the Titration Period).

Results

In the mITT population (n = 73), 46 patients were 4‐mg/d responders; of whom, 37 (80.4%) were early responders and nine (19.6%) were later responders. The mean (standard deviation) percent reductions in FOS frequency from baseline at the end of the 4‐mg/d Titration Period were 100.0% (0.0%; early responders) and 46.3% (97.3%; later responders). Among the 27 4‐mg/d nonresponders, nine (33.3%) patients who had an early response experienced seizure(s) during the subsequent 4‐mg/d Maintenance Period. Safety outcomes were similar, regardless of responder status, without new safety concerns.

Significance

Some patients with untreated FOS may benefit from continued treatment beyond initial titration of perampanel monotherapy to achieve seizure freedom, suggesting that it may not be appropriate to make treatment decisions to discontinue or switch from perampanel monotherapy solely based on seizure response before an effective dose has been reached.

Additional baricitinib loading dose improves clinical outcome in COVID-19

Pneumonia associated with coronavirus disease 2019 (COVID-19) has been accounted for high mortality rate in severe COVID-19 worldwide, and additional serious scarcity of standard and effective anti-inflammatory drug in COVID-19 pneumonia management is a big challenge. Baricitinib, a Janus kinase (JAK) inhibitor, is a promising drug in COVID-19 pneumonia. This study aims to compare the clinical outcome of moderate-to-severe COVID-19 pneumonia treated with baricitinib with or without a loading dose. This prospective case-control study enrolled 37 adult patients where 17 patients (control) received baricitinib at 4 mg oral daily dose and 20 patients (case) received an additional single 8 mg oral loading dose. The median day to gain blood oxygen saturation level ≥95% (in room air) and return in normal breathing function were lower in case group than the control group. The requirement of intensive care unit and mechanical ventilation support was higher in the control group than in the case group [29.4% (N = 17)/10% (N = 20), P < 0.05; 11.8% (N = 17)/5% (N = 20), P > 0.05), respectively]. Thus, an additional loading dose of baricitinib revealed better clinical outcome of patients with COVID-19 pneumonia.

Quality of life of children aged 8-12 years undergoing food allergy oral immunotherapy: Child and parent perspective

BACKGROUND

Oral immunotherapy (OIT) for food allergy improves the quality of life (QOL) of children from parental perspective but little is known about the child perception.

METHODS

The Food Allergy Quality of Life Questionnaire-Child Form (FAQLQ-CF) was administered to children aged 8-12 years, and the FAQLQ-Parent Form (FAQLQ-PF) was administered to their parents at the start of OIT for milk, egg, peanut, sesame, or tree nuts, at the end of up-dosing, and after 6 months of follow-up. Food-allergic children not undergoing OIT served as controls. Children QOL scores were compared to their parents.

RESULTS

The total FAQLQ-CF score of 103 children undergoing OIT improved significantly from start of OIT (median (IQR); 4.8, 3.8-5.7) to end of up-dosing (3.9, 3-5.2) (P < .001). A greater improvement was noted in the 56 children who reached a follow-up visit, from 5.0 (3.7-5.8) at OIT start to 3.1 (1.8-5.0) on follow-up, (P < .001). In contrast, FAQLQ-CF scores of control patients improved mildly and nonsignificantly between the two time points from 5.3 (4.3-5.7) to 4.8 (3.6-6.0), (P = .13). The improvement in the total FAQLQ-CF scores from OIT start to follow-up was significantly greater compared to the change in control patients during observation (P = .015). Parents reported better QOL scores compared to their children at all stages of OIT (start 4.0, 3.2-5, P = .004; end of up-dosing 2.9, 1.9-4.7, P = .04; follow-up 2.2, 1.6-3.6, P = .003).

CONCLUSIONS

QOL of food-allergic children undergoing OIT improves significantly compared to controls. Parents perceive QOL to be better than the perception of the children.

In Vivo Efficacy of VT-1129 against Experimental Cryptococcal Meningitis with the Use of a Loading Dose-Maintenance Dose Administration Strategy

VT-1129 is a novel fungal enzyme-specific Cyp51 inhibitor with potent cryptococcal activity. Because of its long half-life (>6 days in mice) and our desire to quickly reach potent efficacy, we evaluated a VT-1129 loading dose-maintenance dose strategy against cryptococcal meningitis. VT-1129 plasma and brain pharmacokinetics were first studied in healthy mice, and these data were used to model loading dose-maintenance dose regimens to generate different steady-state concentrations. Mice were inoculated intracranially with Cryptococcus neoformans, and oral treatment began 1 day later. Treatment consisted of placebo or one of three VT-1129 loading dose-maintenance dose regimens, i.e., loading dose of 1, 3, or 30 mg/kg on day 1, followed by once-daily maintenance doses of 0.15, 0.5, or 5 mg/kg, respectively. In the fungal burden arm, therapy continued for 14 days and brains were collected on day 15 for fungal burden assessments. In the survival arm, treatment continued for 10 days, after which mice were monitored without therapy until day 30. VT-1129 plasma and brain concentrations were also measured. All VT-1129 doses significantly improved survival and reduced fungal burdens, compared to placebo. VT-1129 plasma and brain levels correlated with fungal burden reductions (R ² = 0.72 and R ² = 0.67, respectively), with a plasma concentration of 1 μg/ml yielding a reduction of ∼5 log₁₀ CFU/g. With the highest loading dose-maintenance dose regimen, fungal burdens were undetectable in one-half of the mice in the fungal burden arm and in one-fourth of the mice in the survival arm, 20 days after the final dose. These data support a loading dose-maintenance dose strategy for quickly reaching highly efficacious VT-1129 concentrations for treating cryptococcal meningitis.

Long-term outcome of peanut oral immunotherapy-Real-life experience

BACKGROUND

Oral immunotherapy (OIT) is currently recommended as a treatment option for peanut-allergic patients. Data regarding its long-term compliance and efficacy in real life are required.

METHODS

Peanut-allergic patients aged ≥4 years were enrolled in a single-center clinical OIT program. Buildup to 3000 mg peanut protein was performed. Patients reaching this dose before or after 12/2014 were instructed to consume 3000 or 1200 mg daily, respectively. Patients were followed ≥6 months after reaching maintenance and rechallenged to 3000 mg.

RESULTS

Of the 145 patients studied, 113 (77.9%) were fully desensitized to 3000 mg and 133 (91.7%) were desensitized to ≥300 mg. 21/145 patients (14.5%) required adrenaline for home-dose reactions during buildup. Non-anaphylactic gastrointestinal symptoms, experienced by 9 patients (6.2%), reversed with dose reduction. Of the 111 patients available for analysis 6 months after reaching 3000 mg, 97 (87.4%) continued regular peanut consumption. Only 2/111 patients (1.8%) required adrenaline over the long-term (median, range; 18, 6-75 months) follow-up. Adherence to treatment was significantly higher in patients consuming 1200 mg (73/76, 96.1%) vs those consuming 3000 mg (24/35, 72.2%), (P = .001). A higher maintenance dosage and home adrenaline requirement during buildup predicted adherence cessation (OR 12.5, P = .001; and OR 7.8, P = .02, respectively). 63/64 patients (98.4%) consuming 1200 mg maintenance dose were successfully rechallenged to 3000 mg.

CONCLUSIONS

This real-life experience demonstrates the efficacy of peanut OIT long-term. A lower maintenance dose minimized treatment cessation while maintaining desensitization. OIT should be performed in qualified centers given the prevalence of adverse reactions, particularly during buildup.

Caffeine Citrate Dosing Adjustments to Assure Stable Caffeine Concentrations in Preterm Neonates

OBJECTIVE

To identify dosing strategies that will assure stable caffeine concentrations in preterm neonates despite changing caffeine clearance during the first 8 weeks of life.

METHODS

A 3-step simulation approach was used to compute caffeine doses that would achieve stable caffeine concentrations in the first 8 weeks after birth: (1) a mathematical weight change model was developed based on published weight distribution data; (2) a pharmacokinetic model was developed based on published models that accounts for individual body weight, postnatal, and gestational age on caffeine clearance and volume of distribution; and (3) caffeine concentrations were simulated for different dosing regimens.

RESULTS

A standard dosing regimen of caffeine citrate (using a 20 mg/kg loading dose and 5 mg/kg/day maintenance dose) is associated with a maximal trough caffeine concentration of 15 mg/L after 1 week of treatment. However, trough concentrations subsequently exhibit a clinically relevant decrease because of increasing clearance. Model-based simulations indicate that an adjusted maintenance dose of 6 mg/kg/day in the second week, 7 mg/kg/day in the third to fourth week and 8 mg/kg/day in the fifth to eighth week assures stable caffeine concentrations with a target trough concentration of 15 mg/L.

CONCLUSIONS

To assure stable caffeine concentrations during the first 8 weeks of life, the caffeine citrate maintenance dose needs to be increased by 1 mg/kg every 1-2 weeks. These simple adjustments are expected to maintain exposure to stable caffeine concentrations throughout this important developmental period and might enhance both the short- and long-term beneficial effects of caffeine treatment.

Association Between the Lower Extremity Deep Venous Thrombosis, the Warfarin Maintenance Dose, and CYP2C9*3, CYP2D6*10, and CYP3A5*3 Genetic Polymorphisms: A Case-Control Study

OBJECTIVE

This study explored the association between the CYP2C9*3/CYP2D6*10/CYP3A5*3 genetic polymorphisms with lower extremity deep venous thrombosis (LEDVT) and the warfarin maintenance dose.

METHODS

Five hundred thirty-six patients who were pathologically diagnosed with LEDVT after surgery were included in the LEDVT group. At the same time, 540 patients without LEDVT who underwent surgery were recruited as the control group. Patients were given warfarin at an initial dose of 2.5-3.0 mg. Blood samples were collected to detect the initial and stable international normalized ratio (INR) values. The warfarin maintenance dose was obtained if the INR remained within a range of 2.0-3.0 for 3 consecutive days. The genotype distribution and haplotype analysis of the CYP2C9*3/CYP2D6*10/CYP3A5*3 alleles were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) testing and SHEsis software, respectively. Logistic regression analysis was used to analyze the risk and protective factors for LEDVT.

RESULTS

The A/G genotypes, G/G genotypes, and G allele of CYP3A5*3 in the LEDVT group were observed with increased frequency compared with the control group. The LEDVT group displayed a higher ACG haplotype frequency, and lower ACA and ATA haplotype frequencies than the control group. Age, diabetes, low-density lipoprotein, CYP3A5*3 and the ACG haplotype were independent risk factors for LEDVT. High-density lipoprotein and the ACA haplotype were independent protective factors for LEDVT. The genotype distributions of the CYP2C9*3, CYP2D6*10, and CYP3A5*3 genetic polymorphisms were associated with the warfarin maintenance dose.

CONCLUSION

The CYP3A5*3 genetic polymorphism may be an important risk factor for LEDVT. Moreover, CYP2C9*3, CYP2D6*10, and CYP3A5*3 are associated with the warfarin maintenance dose.

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

AIMS

Methadone is characterized by wide intersubject variability regarding the dose needed to obtain full therapeutic response. We assessed the influence of sociodemographic, ethnic, clinical, metabolic and genotypic variables on methadone maintenance dose requirement in opioid-dependent responder patients.

METHODS

Eighty-one stable patients (60 men and 21 women, 43.7 ± 8.1 years old, 63.1 ± 50.9 mg day(-1) methadone), divided into quartiles with respect to the median daily dose, were enrolled and underwent clinical examination, treatment history and determination of liver/intestinal cytochrome P450 (CYP) 3A4 activity measured by the midazolam test, R,S-methadone trough concentration and clinically significant polymorphisms of the OPRM1, DRD2, COMT, ABCB1, CYP2B6, CYP3A5, CYP2C19 and CYP2D6 genes.

RESULTS

Methadone maintenance dose was correlated to the highest dose ever used (r(2) = 0.57, P < 0.0001). Fractioned methadone intake (odds ratio 4.87, 95% confidence interval 1.27-18.6, P = 0.02), bodyweight (odds ratio 1.57, 95% confidence interval 1.01-2.44, P = 0.04), history of cocaine dependence (80 vs. 44 mg day(-1) in never-addict patients, P = 0.005) and ethnicity (Asian > Caucasian > African, P = 0.04) were independently associated with high-dose methadone in multiple regression analysis. A modest correlation was observed between liver/intestinal CYP3A4 activity and methadone dose at steady state (Spearman rank correlation coefficient [rs ] = 0.21, P = 0.06) but not with highest dose ever used (rs = 0.15, P = 0.18) or dose-normalized R,S-methadone trough concentrations (rs = -0.05, P = 0.64). Concomitant CYP3A4 inhibitors only affected the relationship between methadone dose and R,S-methadone trough concentration. None of the genetic polymorphisms explored was predictive of the methadone maintenance dose.

CONCLUSIONS

Methadone maintenance dose was predicted by sociodemographic and clinical variables rather than genetic polymorphisms or liver/intestinal CYP3A4 activity in stable patients.

Drug-gene interactions: inherent variability in drug maintenance dose requirements

The influence of genetics on pharmacokinetics can introduce variability among individual patients that may cause treatment failure, toxicity, or both. Such variability, specifically in clearance rates, can influence drug maintenance dosing regimens.

Effect of Methadone Dose on Maintenance Treatment and Health Consequences Among Heroin Addicts in South China

A retrospective cross-sectional study was conducted with a convenience sample of 197 adults receiving methadone maintenance treatment in Kunming city, South China, in 2010. The aim of the study was to determine the association of methadone maintenance dose on a variety of treatment outcomes. Treatment modalities, the adverse reactions to methadone treatment, the physical and mental outcomes of the treatment, and risk behavior changes were assessed. Multilevel negative and logistic binomial regression analyses were carried out, which demonstrated that methadone maintenance dose in this sample was not associated with improved treatment adherence or with quality of life. We concluded that dose had a small, if negligible, influence on the changes in adverse effects of methadone. Further research in dose differences between the genders should be conducted.