A semiphysiological population pharmacokinetic model of agomelatine and its metabolites in Chinese healthy volunteers

Agomelatine's antiglycoxidative action-In vitro and in silico research and systematic literature review

Introduction

Agomelatine is an atypical antidepressant drug enhancing norepinephrine and dopamine liberation; nevertheless, additional mechanisms are considered for the drug's pharmacological action. Since protein glycoxidation plays a crucial role in depression pathogenesis, agomelatine's impact on carbonyl/oxidative stress was the research purpose.

Methods

Reactive oxygen species scavenging (hydroxyl radical, hydrogen peroxide, and nitrogen oxide) and antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl radical and ferrous ion chelating assays) of agomelatine were marked. Agomelatine's antiglycoxidation properties were assayed in sugars (glucose, fructose, and galactose) and aldehydes- (glyoxal and methylglyoxal) glycated bovine serum albumin (BSA). Aminoguanidine and α-lipoic acid were used as standard glycation/oxidation inhibitors.

Results

Agomelatine did not show meaningful scavenging/antioxidant capacity vs. standards. Sugars/aldehydes increased glycation (↑kynurenine, ↑N-formylkynurenine, ↑dityrosine, ↑advanced glycation end products, and ↑β-amyloid) and oxidation (↑protein carbonyls and ↑advanced oxidation protein products) parameters in addition to BSA. Standards restored BSA baselines of glycation and oxidation markers, unlike agomelatine which sometimes even intensifies glycation above BSA + glycators levels. Molecular docking analysis of agomelatine in BSA demonstrated its very weak binding affinity.

Discussion

Agomelatine's very low affinity to the BSA could proclaim non-specific bonding and simplify attachment of glycation factors. Thereby, the drug may stimulate brain adaptation to carbonyl/oxidative stress as the systematic review indicates. Moreover, the drug's active metabolites could exert an antiglycoxidative effect.

CYP1A2 polymorphism may contribute to agomelatine-induced acute liver injury: Case report and review of the literature

RATIONALE

Liver function monitoring is recommended when agomelatine is prescribed, although liver enzymes are not considered predictive biomarkers. Most patients present with acute liver injury, with only a few presenting with levels of liver enzymes that are over 30 times the upper limit of normal. The patient-specific risk factors that are associated with liver injury remain unclear. Thus, this report provides new insights into the mechanism of agomelatine-induced acute hepatocellular injury based on cytochrome P450 family 1 subfamily A member 2 (CYP1A2) polymorphism.

PATIENT CONCERNS

We present a case of acute hepatocellular injury in a 75-year-old man who was taking agomelatine at a dose of 50 mg/qn. All hepatitis virus test results were negative. No history of liver disease was observed. As CYP1A2 is the main metabolic enzyme of agomelatine, CYP1A2 AA (rs762551) genetic polymorphism was analyzed.

DIAGNOSIS

The patient's transaminases level exceeded the critical value on day 72 after starting oral agomelatine.

INTERVENTIONS

The patient received intravenous magnesium isoglycyrrhizinate, a liver cell-protecting agent, followed by the withdrawal of agomelatine.

OUTCOMES

There was an improvement in the levels of the liver enzymes and no subsequent organ dysfunction was observed.

LESSONS

Here, we report a case of acute hepatocellular injury characterized by a very high aspartate aminotransferase level. Periodic liver function testing throughout the treatment period can help in the rapid and appropriate diagnosis of acute liver injury, particularly in the absence of typical clinical manifestations. Agomelatine hepatic toxicity might be related to an idiosyncratic metabolic reaction that depends on individual patient differences. As it is the main metabolic enzyme of agomelatine, CYP1A2 genetic polymorphism may contribute to liver injury by affecting its metabolites.

A semiphysiological population pharmacokinetic model of agomelatine and its metabolites in Chinese healthy volunteers

AIMS

Agomelatine is an antidepressant for major depressive disorders. It undergoes extensive first-pass hepatic metabolism and displays irregular absorption profiles and large interindividual variability (IIV) and interoccasion variability of pharmacokinetics. The objective of this study was to characterize the complex pharmacokinetics of agomelatine and its metabolites in healthy subjects.

METHODS

Plasma concentration-time data of agomelatine and its metabolites were collected from a 4-period, cross-over bioequivalence study, in which 44 healthy subjects received 25 mg agomelatine tablets orally. Nonlinear mixed effects modelling was used to characterize the pharmacokinetics and variability of agomelatine and its metabolites. Deterministic simulations were carried out to investigate the influence of pathological changes due to liver disease on agomelatine pharmacokinetics.

RESULTS

A semiphysiological pharmacokinetic model with parallel first-order absorption and a well-stirred liver compartment adequately described the data. The estimated IIV and interoccasion variability of the intrinsic clearance of agomelatine were 130.8% and 28.5%, respectively. The IIV of the intrinsic clearance turned out to be the main cause of the variability of area under the curve-based agomelatine exposure. Simulations demonstrated that a reduction in intrinsic clearance or liver blood flow, and an increase in free drug fraction had a rather modest influence on agomelatine exposures (range: -50 to 200%). Portosystemic shunting, however, substantially elevated agomelatine exposure by 12.6-109.1-fold.

CONCLUSIONS

A semiphysiological pharmacokinetic model incorporating first-pass hepatic extraction was developed for agomelatine and its main metabolites. The portosystemic shunting associated with liver disease might lead to significant alterations of agomelatine pharmacokinetics, and lead to substantially increased exposure.