Association of the OPRM1 variant rs1799971 (A118G) and clinical manifestations in tramadol poisoned patients: a cross-sectional study

Abstract

Introduction

The opioid receptor mu1 is a protein coding gene that can have different codes for a protein and may have variations (polymorphisms) affecting how opioids work. The aim of this study was to investigate the prevalence of the most common opioid receptor mu1 polymorphism (A118G) and any relationship between this polymorphism and features following tramadol overdose.

Materials and methods

This was a cross-sectional study of patients admitted with tramadol poisoning to an Iranian hospital. These patients were not taking any other drugs or medications and had no history of seizures.

Results

The results showed that among the 83 patients included in the study, 57 (69 per cent) had the AA genotype, 25 (30 per cent) had the AG genotype, and one (1 per cent) had the GG genotype for the opioid receptor mu1 A118G polymorphism. Nausea and/or vomiting occurred in nine (11 per cent) patients and dizziness in 38 (46 per cent) patients. Serious adverse events included seizures in 51 (60 per cent) patients and respiratory failure requiring mechanical ventilation in 21 (25 per cent) patients. However, there was no significant association between the opioid receptor mu1 A118G polymorphism and these adverse events.

Discussion

In our study, the frequency of the A allele was greater than the G allele, and the AA genotype was more prevalent than AG. The GG genotype was the least common among the polymorphisms of opioid receptor mu1 rs1799971. There was no significant association between the opioid receptor mu1 A118G polymorphism and symptoms in tramadol-poisoned patients. Although these allele proportions are similar to the results reported in other Caucasian populations, they are dissimilar to the findings in Chinese and Singaporean populations. In these Asian studies, the predominant allele was the G allele. It has been suggested that a mutated G allele will decrease the production of opioid receptor mu1-related messenger ribonucleic acid and related proteins, leading to fewer mu-opioid receptors in the brain.

Conclusions

This study found no significant association between the opioid receptor mu1 A118G polymorphism and adverse outcomes in tramadol-poisoned patients. However, more research is needed to draw more definitive conclusions due to the limited evidence and variability of opioid receptor mu1 polymorphisms in different populations.

Keywords:

• mu opioid receptors
• opioid poisoning
• opioid receptor mu1 polymorphism
• overdose
• seizure
• tramadol

Contributors

AE, and HHM contributed to the conception and design of the study. SSD and ME organized the database. AE and AAK performed the statistical analysis. NZ wrote the first draft of the manuscript. SKH, AE and HHM wrote sections of the manuscript. AM made substantial revisions. All authors contributed to the manuscript revision and approved the submitted version.

Disclosure statement

No potential conflicts of interest were reported by the authors.