Relationship of the 1846G > A Polymorphism of the CYP2D6 Gene to the Equilibrium Concentration Levels of Haloperidol in Patients with Acute Alcoholic Hallucinosis

Abstract

Haloperidol is currently used in addictology for the treatment of acute psychotic disorders, including acute alcoholic hallucinosis. The use of haloperidol is often accompanied by the occurrence of adverse drug reactions (ADRs). There is evidence that CYP2D6 isoenzyme is involved in the biotransformation of haloperidol.

Aim

The study aimed to evaluate the relationship of 1846G > A polymorphism of the CYP2D6 gene to the equilibrium concentration levels of haloperidol in patients with acute alcoholic hallucinosis.

Material and Methods

The study was conducted on 100 male patients with acute alcoholic hallucinosis (mean age 41.4 ± 14.4 years). The efficacy profile was evaluated using the PANSS (Positive and Negative Syndrome Scale) scale. The safety of therapy was assessed using the UKU Side-Effect Rating Scale and the SAS (Simpson-Angus Scale for Extrapyramidal Symptoms) scale. Genotyping was performed using the real-time polymerase chain reaction (Real-time PCR). Equilibrium plasma concentration levels of haloperidol were investigated using the high-performance liquid chromatography with mass spectrometry (HPLC with MS/MS).

Results

No statistically significant results were obtained during the therapy efficacy assessment (dynamics of the PANSS score: GG genotype (−13.00 [−16.00; −16.00; −11.00]), GA genotype (−15.00 [−16.75; −13.00], p = 0.728). There was a statistically significant difference in safety assessment scores (dynamics of the UKU score: GG genotype (8.00 [7.00; 10.00]), GA genotype (15.00 [9.25; 18.00], p < 0.001); dynamics of the SAS score: GG genotype (11.00 [9.00; 14.00]), GA genotype (14.50 [12.00; 18.00], p < 0.001). The pharmacokinetic study results showed a statistically significant difference: GG (3.13 [2.32; 3.95]), GA (3.89 [2.92; 5.26], p = 0.010). Thus, a study conducted on a group of 100 patients with acute alcoholic hallucinosis demonstrated an association between the 1846G > A polymorphism of the CYP2D6 gene (rs3892097) and the safety profile of haloperidol therapy. We also revealed the presence of statistically significant difference in the equilibrium concentration levels of haloperidol in patients with the GG and AG genotypes.

Conclusion

It can be concluded that patients with the GA genotype have a higher risk of ADRs compared to patients carrying the GG genotype. It is shown that 1846G > A polymorphism of the CYP2D6 gene (rs3892097) has a statistically significant effect on the equilibrium concentration levels of haloperidol.

Introduction

Alcoholic hallucinosis is a mental disorder characterized by the acute onset, with predominating auditory hallucinations.¹ The incidence of this disorder ranges from 0.4% to 12%.² Alcoholic hallucinosis is treated in hospitals, typically with antipsychotic drugs. Haloperidol at a dose of 5–10 mg per day is usually prescribed.³ When using haloperidol, adverse drug reactions such as akathisia and dystonia often occur.⁴

Studies revealed that haloperidol metabolism occurs with the participation of cytochrome P450 (CYP) 2D6 isoenzyme.⁵ Polymorphism of the CYP2D6 gene (CYP2D6*4, CYP2D6 1846G > T, rs3892097) is the most studied genetic polymorphism leading to deactivation of CYP2D6 isoenzyme and the reduced metabolism of the substrate drugs.⁶

Studies conducted on patients with alcohol use disorders have shown a statistically significant correlation between the CYP2D6 genetic polymorphism, isoenzyme activity and the efficacy and safety rates of haloperidol.^7,8

Studies conducted on patients with alcohol use disorders who received haloperidol in injections demonstrated a relationship between the 1846G > A polymorphism of the CYP2D6 gene (rs3892097) and haloperidol equilibrium concentration levels in plasma (p = 0.037).⁹

The aim of this study was to evaluate the relationship of the 1846G > A polymorphism of the CYP2D6 gene to the equilibrium concentration levels of haloperidol in patients with acute alcoholic hallucinosis.

Material and Methods

The study enrolled 100 male patients (average age—41.4 ± 14.4 years) with acute alcoholic hallucinosis (alcohol-induced psychotic disorder with hallucinations (F10.52), according to ICD-10) who underwent inpatient treatment at Moscow Research and practical center on Addictions. Haloperidol in injections at a dose of 5–10 mg/day was administered to this cohort of patients for the treatment of acute hallucinatory symptoms. Haloperidol therapy was initiated from the moment of the patient’s admission to the emergency department and lasted for 5 days. Along with haloperidol, all patients received minimal standard therapy for 5 days, which included infusions, ion-containing solutions, and vitamins.

The inclusion criteria were the signed informed consent to participate in the study; the diagnosis of alcohol-induced psychotic disorder with hallucinations (F10.52, according to ICD-10); 5 days of haloperidol treatment.

The exclusion criteria were creatinine clearance values < 50 mL/min, creatinine plasma concentration > 1.5 mg/dL (133 mmol/L), body weight less than 60 kg or greater than 100 kg, age ≥ 75 years, presence of any other psychotropic medications in the treatment regimen other than haloperidol, presence of chronic psychotic disorders, and presence of any contraindications for haloperidol use.

Each patient signed an informed consent for voluntary participation in the study (Protocol No. 14 of October 27, 2020), which was approved by the local ethical committee of the Russian Medical Academy of Continuing Professional Education of the Ministry of Health of Russia.

For genotyping, venous blood samples were collected on the day 6 of haloperidol therapy using the VACUETTE® vacuum tubes (GreinerBio-One, Austria). The 1846G > A polymorphism of the CYP2D6 gene (rs3892097) was analyzed by real-time PCR using “Dtlite” DNA amplifiers (DNA Technology, Moscow, Russia) on a CFX96 Touch Real-Time System with CFX Manager software (Bio-Rad Laboratories Inc., Hercules, CA, USA) and the “SNP-screen” sets (Syntol, Moscow, Russia). In every set, two allele-specific hybridizations were used, which allowed simultaneous determination of both alleles of the respective SNP using two fluorescence channels.

Therapeutic drug monitoring of haloperidol was performed by evaluating the equilibrium plasma concentration levels of haloperidol using the high-performance liquid chromatography with mass spectrometry (HPLC with MS/MS). Calibration and control samples were prepared from working standard solutions by dissolving an accurate suspension of the standard sample in methanol followed by dilution to obtain the desired concentrations. To construct the calibration curve, calibration samples were prepared with haloperidol concentrations of 5, 10, 20, 50, 100, 200, 500, 1000, 2000 ng/mL, and control samples with diazepam concentrations of 5 (lower limit of quantification, LLOQ), 15 (low QC), 1000 (medium QC), 1500 ng/mL (high QC). Droperidol at a concentration of 250 ng/mL in acetonitrile was used as an internal standard (IS).

The efficacy of haloperidol therapy was assessed using the PANSS positive subscale.¹⁰ The safety profile of haloperidol therapy was assessed using the UKU Side Effect Rating Scale.¹¹ and the Simpson-Angus Extrapyramidal Side Effects Scale (SAS).¹² Scale scoring and biomaterial collection were performed on days 1 and 6 of haloperidol treatment.

Statistical analysis was performed in StatsoftStatistica v. 10.0 (Dell Statistica, Tulsa, OK, USA). Statistical analysis of the study results was performed using the methods of nonparametric statistics due to the absence of normal distribution of data, which was checked using the Shapiro-Wilk W-test. The Mann-Whitney U-test was used to compare two samples of continuous independent data, and the Wilcoxon test was used to compare two samples of dependent data. In the case of multiple comparisons, we calculated the adjusted p-values using the Benjamini-Hochberg procedure. Research data are presented in the form of the median and interquartile range (Me [Q1; Q3]).

Results

CYP2D6 genotyping by the polymorphic marker 1846G > A (rs3892097) performed in 100 male patients with acute alcoholic hallucinosis revealed the following data:

• 1) The number of patients who were homozygous carriers (genotype GG) of the 1846G > A polymorphism of the CYP2D6 gene was 70 (70%).

• 2) The number of patients who were heterozygous carriers (genotype GA) of the 1846G > A polymorphism of the CYP2D6 gene was 30 (30%).

The results of data analysis performed for psychometric assessments (PANSS) and side-effect rating scales (UKU and SAS) on days 1 and 6 in patients who received haloperidol are presented in Table 1.

Table 1. Data from the Psychometric Assessments and Side-Effect Rating Scales in Patients Who Received Haloperidol, on Days 1 and 6 of the Study.

Scale		GG (N = 70)		GA (N = 30)		P*
Day 1
PANSS		14.50 [13.00; 18.00]		16.00 [15.00; 18.00]		> 0.999
SAS		0 [0; 0]		0 [0; 0]		> 0.999
UKU		0 [0; 0]		0 [0; 0]		> 0.999
Day 6
PANSS		1.00 [1.00; 2.00]		2.00 [1.00; 2.75]		0.006
SAS		11.00 [9.00; 14.00]		14.50 [12.00; 18.00]		< 0.001
UKU		8.00 [7.00; 10.00]		15.00 [9.25; 18.00]		< 0.001

p* – p-value obtained in Benjamini-Hochberg multiple testing correction (based on the results of Mann-Whitney U test).

Then we compared the dynamics of changes in the PANSS positive subscale scores in patients with the GG and GA genotypes. Statistical analysis of the data on the clinical efficacy profile of haloperidol in patients with different genotypes showed no statistically significant differences: GG (−13.00 [−16.00; −11.00]), GA (−15.00 [−16.75; −13.00]), p = 0.078.

Table 2 presents the dynamics of changes in the SAS and UKU scores in patients with different genotypes. Statistical analysis of the data on the safety profile of haloperidol in patients with different genotypes by the 1846G > A polymorphic marker of the CYP2D6 gene showed statistically significant differences.

Table 2. Dynamics of Changes in the SAS and UKU Scores from Days 1 to 6 in Patients with Different Genotypes by the 1846G > A Polymorphic Marker of the CYP2D6 Gene.

Scale		GG		GA		P
SAS		11.00 [9.00; 14.00]		14.50 [12.00; 18.00]		p < 0.001
UKU		8.00 [7.00; 10.00]		8.00 [7.00; 10.00]		p < 0.001

Table 3 presents the results of pharmacokinetic study in patients carrying the GG and GA genotypes.

Table 3. Equilibrium Concentration Levels of Haloperidol in Patients with Different Genotypes by the 1846G > A Polymorphic Marker of the CYP2D6 Gene.

GG		GA		P
3.13 [2.32; 3.95]		3.89 [2.92; 5.26]		0.010

The 1846G > A polymorphism of the CYP2D6 gene (rs3892097) was shown to have a statistically significant effect on the equilibrium concentration levels of haloperidol when administered to patients with acute alcoholic hallucinosis (Figure 1).

Figure 1.

Effect of the 1846G > A Polymorphism of the CYP2D6 Gene (RS3892097) on the Equilibrium Concentration Levels of Haloperidol

Discussion

Thus, the results of the study showed no statistically significant differences in the efficacy rates of haloperidol therapy in patients with acute alcoholic hallucinosis carrying different genotypes by the polymorphic marker 1846G > A of the CYP2D6 gene. Meanwhile, a statistically significant difference in the safety parameters assessed by the UKU and SAS scales was revealed. The dynamics of changes was more pronounced in the group of patients with the GA genotype compared to those who were carriers of the GG genotype. The equilibrium concentration levels of haloperidol showed a statistically significant difference between the carriers of the GG and GA genotypes, which confirms the influence of the CYP2D6 genetic polymorphism on haloperidol concentrations in patients with acute alcoholic hallucinosis.

The results of our study coincide with the results of a study demonstrating an increased incidence of ADRs in patients with alcohol addction treated with haloperidol.⁹ Also, there is evidence from a study that the CYP2D6 genetic polymorphism (1846G > A) may affect the concentration levels of haloperidol in patients with alcohol use disorders.⁹

Patients with the GA genotype should have the starting dose of haloperidol reduced by 25%, and homozygous GG carriers are recommended to be prescribed haloperidol at the standard therapeutic dose. According to the DPWG guidelines, a 50% reduction in the starting dose of haloperidol is recommended for mutant homozygotes.¹³ According to our study, a worsening of the safety profile was observed in heterozygous carriers; therefore, it is necessary to adjust the starting dose of haloperidol for this group.

Conclusion

Thus, an association between the 1846G > A polymorphism of the CYP2D6 gene (rs3892097) and the safety profile of haloperidol was demonstrated in a study conducted on 100 patients with acute alcoholic hallucinosis. A statistically significant difference in the equilibrium concentration levels of haloperidol was found between the carriers of the GG and GA genotypes, confirming the influence of the CYP2D6 genetic polymorphism on haloperidol concentration levels in patients with acute alcoholic hallucinosis.