Interaction between antidepressants and alpha 1-adrenergic receptor antagonists on the binding to alpha 1-acid glycoprotein

Precision Medicine in Antidepressants Treatment

Precision medicine uses innovative approaches to improve disease prevention and treatment outcomes by taking into account people's genetic backgrounds, environments, and lifestyles. Treatment of depression is particularly challenging, given that 30-50% of patients do not respond adequately to antidepressants, while those who respond may experience unpleasant adverse drug reactions (ADRs) that decrease their quality of life and compliance. This chapter aims to present the available scientific data that focus on the impact of genetic variants on the efficacy and toxicity of antidepressants. We compiled data from candidate gene and genome-wide association studies that investigated associations between pharmacodynamic and pharmacokinetic genes and response to antidepressants regarding symptom improvement and ADRs. We also summarized the existing pharmacogenetic-based treatment guidelines for antidepressants, used to guide the selection of the right antidepressant and its dose based on the patient's genetic profile, aiming to achieve maximum efficacy and minimum toxicity. Finally, we reviewed the clinical implementation of pharmacogenomics studies focusing on patients on antidepressants. The available data demonstrate that precision medicine can increase the efficacy of antidepressants and reduce the occurrence of ADRs and ultimately improve patients' quality of life.

Toxicokinetic evaluation during intoxication of psychotropic drugs using brain microdialysis in mice

In the event of an overdose, the pharmacokinetics of the drug may be altered, resulting in an unexpectedly rapid increase in blood and tissue drug concentrations. Because central nervous system (CNS)-acting drugs are the major cause of hospitalization for overdose, brain concentrations, which are closely related to the development of acute psychotropic symptoms, would be important. However, due to the lack of an appropriate model for overdose, it is difficult to predict the CNS symptoms of patients with acute poisoning. To clarify the toxicokinetics during intoxication with CNS-acting drugs, we investigated the relationship between the dose and concentrations in the blood and brain in mice. Therapeutic or toxic doses of phenobarbital, flunitrazepam, imipramine, and amoxapine were administered intraperitoneally to mice. Serum and extracellular fluid of the brain were collected up to 24 hr after administration and analyzed using LC-MS/MS to determine the pharmacokinetic parameters in the serum and brain. A comparison of the four psychotropic drugs showed that the toxicokinetics of amoxapine in the blood and brain are clearly different from others, with the brain concentrations being specifically highly susceptible to increase during dose escalation. These results are consistent with the CNS-related symptoms observed in amoxapine overdose. Therefore, the methodology of the current study could be useful for predicting CNS toxicity during psychotropic drug poisoning.

Exploring the interaction between Salvia miltiorrhiza and human serum albumin: Insights from herb-drug interaction reports, computational analysis and experimental studies

Human serum albumin (HSA) binding is one of important pharmacokinetic properties of drug, which is closely related to in vivo distribution and may ultimately influence its clinical efficacy. Compared to conventional drug, limited information on this transportation process is available for medicinal herbs, which significantly hampers our understanding on their pharmacological effects, particularly when herbs and drug are co-administrated as polytherapy to the ailment. Several lines of evidence suggest the existence of Salvia miltiorrhiza-Warfarin interaction. Since Warfarin is highly HSA bound in the plasma with selectivity to site I, it is critical to evaluate the possibility of HSA-related herb-drug interaction. Herein an integrated approach was employed to analyze the binding of chemicals identified in S. miltiorrhiza to HSA. Molecular docking simulations revealed filtering criteria for HSA site I compounds that include docking score and key molecular determinants for binding. For eight representative ingredients from the herb, their affinity and specificity to HSA site I was measured and confirmed fluorometrically, which helps to improve the knowledge of interaction mechanisms between this herb and HSA. Our results indicated that several compounds in S. miltiorrhiza were capable of decreasing the binding constant of Warfarin to HSA site I significantly, which may increase free drug concentration in vivo, contributing to the herb-drug interaction observed clinically. Furthermore, the significance of HSA mediated herb-drug interactions was further implied by manual mining on the published literatures on S. miltiorrhiza.

In vitro enantioselective displacement of propranolol from protein binding sites by acetyl salicylic acid and salicylic acid

The influences of acetyl salicylic acid (ASA) and salicylic acid (SA) on the enantioselective binding of propranolol (PL) and its enantiomers to plasma proteins and human serum albumin (HSA) were investigated. The equilibrium dialysis was employed for protein binding studies. We observed statistically significant displacement of racemic-PL, (+)-(R)-PL, and (-)-(S)-PL (0.1-10 microM) from their protein binding sites by ASA (200 microg/ml) and SA (100 microg/ml). ASA and SA displaced PL stereoselectivly from its binding sites. We concluded that ASA and its metabolite SA could change R/S ratio of PL unbound fractions and they might affect pharmacokinetic properties of PL.

The drug binding site of human α1-acid glycoprotein: Insight from induced circular dichroism and electronic absorption spectra

Human alpha(1)-acid glycoprotein (AGP) is an important drug binding plasma protein which affects pharmacokinetical properties of various therapeutic agents. For the first time, interpretation of the induced circular dichroism (ICD) spectra of drug-AGP complexes is presented yielding valuable information on the protein binding environment. ICD spectra were obtained by novel ligands of which AGP induced optical activity have never been reported (primaquine, mefloquine, propranolol, terazosin, carbamazepine, rhodamine B) and by re-investigation of ICD spectra of protein-bound drugs published earlier (chlorpromazine, dipyridamole, prazosin). Spectroscopic features of the ICD and absorption bands of drugs combined with native AGP indicated chiral non-degenerate exciton coupling between the guest chromophore and the indole ring of an adjacent tryptophan (Trp) residue. Results of additional CD experiments performed by using recombinant AGP mutants showed no changes in the ligand binding ability of W122A in sharp contrast with the W25A which was unable to induce extrinsic CD signal with either ligand. Thus, these findings unequivocally prove that, likely via pi-pi stacking mechanism, Trp25 is essentially involved in the AGP binding of drugs studied here as well as of related compounds. Survey of the AGP binding data published in the literature support this conclusion. Our results provide a fast and efficient spectroscopic tool to determine the inclusion of ligand molecules into the beta-barrel cavity of AGP where the conserved Trp25 is located and might be useful in ligand-binding studies of other lipocalin proteins.

A study of the interaction between ropranolol and NSAIDs in protein binding by gel filtration method

Drug protein binding phenomena can lead to some interesting drug-drug interactions when one drug displaces another in the binding site. Studies of protein binding are conducted by several methods including equilibrium dialysis, ultra-filtration and chromatographic methods. Gel filtration is a simple chromatographic method in protein binding studies. Propranolol binds to plasma proteins by 90%-95% in circulation system and other drugs with high protein binding may displace it. In this study protein binding of propranolol has been studied using gel filtration to Bovine Serum Albumin (BSA) alone and in the presence of Acetyl salicylic acid (ASA), Indomethacin and mefenamic acid has been studied using gel filtration method. The results indicated that ASA decreased protein binding of propranolol by 20% to BSA and other drugs did not displace propranolol from the binding site. Therefore, ASA may alter pharmacological effects of propranolol.

Development of a solid phase extraction for 13 'new' generation antidepressants and their active metabolites for gas chromatographic-mass spectrometric analysis

A solid phase extraction procedure (SPE) for 13 'new' antidepressants (venlafaxine, fluoxetine, viloxazine, fluvoxamine, mianserin, mirtazapine, melitracen, reboxetine, citalopram, maprotiline, sertraline, paroxetine and trazodone) together with eight of their metabolites (O-desmethylvenlafaxine, norfluoxetine, desmethylmianserine, desmethylmirtazapine, desmethylcitalopram, didesmethylcitalopram, desmethylsertraline and m-chlorophenylpiperazine) from plasma is optimized using HPLC-DAD as monitoring system. Special attention has been paid to the choice of washing and eluting solvent, resulting in a highly concentrated, clean and moisture free extract, also suitable for GC-MS. A total number of 10 sorbents (apolar, polymeric, ion-exchange and mixed mode) was evaluated. Based on recovery, reproducibility and absence of interfering substances the strong cation exchanger gave the best results. Recoveries were determined at low and high therapeutic and toxic levels and ranged between 70 and 109% for all compounds, except for trazodone (39%).

Human alpha-1-glycoprotein and its interactions with drugs

For about half a century, the binding of drugs to plasma albumin, the "silent receptor," has been recognized as one of the major determinants of drug action, distribution, and disposition. In the last decade, the binding of drugs, especially but not exclusively basic entities, to another plasma protein, alpha 1-acid glycoprotein (AAG), has increasingly become important in this regard. The present review points out that hundreds of drugs with diverse structures bind to this glycoprotein. Although plasma concentration of AAG is much lower than that of albumin, AAG can become the major drug binding macromolecule in plasma with significant clinical implications. Also, briefly reviewed are the physiological, pathological, and genetic factors that influence binding, the role of AAG in drug-drug interactions, especially the displacement of drugs and endogenous substances from AAG binding sites, and pharmacokinetic and clinical consequences of such interactions. It can be predicted that in the future, rapid automatic methods to measure binding to albumin and/or AAG will routinely be used in drug development and in clinical practice to predict and/or guide therapy.

The effect of the plasticizers TBEP (tris-(2-butoxyethyl)-phosphate) and DEHP (di-(2-ethylhexyl)-phthalate) on beta-adrenergic ligand binding to alpha 1-acid glycoprotein and mononuclear leukocytes

The plasticizers tris-(2-butoxyethyl)-phosphate (TBEP) and di-(2-ethylhexyl)-phthalate (DEHP) and the beta-adrenergic receptor-blockers [3H]-(-)-dihydroalprenolol ([3H]-(-)-DHA) and [3H]-(-)-CGP 12177 were tested for their ability to interact with beta-adrenergic binding to alpha 1-acid glycoprotein (AAG) and mononuclear leukocytes (MNL). The IC50-values, obtained by displacement of [3H]-(-)-DHA bound to AAG, were 3.5 nM, 2 microM and 4 microM for TBEP, (-)-alprenolol and DEHP, respectively. (+/-)-CGP 12177 had virtually no effect on radioligand binding to AAG. The [3H]-(-)-CGP 12177 binding to MNL consisted of beta-adrenergic receptor binding (Kd = 210 pM) and non-saturable binding. [3H]-(-)-DHA was bound to two different classes of binding sites on MNL, the beta-adrenergic receptors (Kd = 440 pM) and a secondary class of binding sites (Kd = 64 nM). (+/-)-CGP 12177 displaced about 30% of [3H]-(-)-DHA from MNL with an IC50-value of 190 pm. (-)-ALP displaced about 85% of total bound radioligand and gave a biphasic displacement curve with IC50-values of 320 pM and 690 mM, respectively. TBEP displaced a considerable fraction of [3H]-(-)-CGP 12177 and [3H]-(-)-DHA bound to MNL beta-adrenergic receptors, whereas DEHP had no effect. In contrast, DEHP caused displacement of [3H]-(-)-DHA from the MNL low affinity sites, but was a markedly less potent displacer compared to TBEP. The present study shows that TBEP and DEHP interact with beta-adrenergic transport proteins, non-specific tissue binding sites and beta-adrenergic receptors coupled to adenylate cyclase. Plasticizers may thus affect the biology and pharmacology of the beta-adrenergic signal system.

Binding of prazosin to alpha 1-acid glycoprotein and albumin: effect of protein purity and concentrations

Prazosin is extensively bound in human serum/plasma. In the present study a bound fraction of 93-95% was observed at 37 degrees for therapeutic drug concentrations. Both alpha 1-acid glycoprotein (AAG) and albumin (HSA) are established as transport proteins for prazosin, but their individual contribution to the extent and variability of protein binding in serum/plasma is unclear. The present study showed that AAG possesses one binding site per molecule with high affinity (Kd approximately 0.8 microM) for prazosin. HSA, essentially globulin-free, bound prazosin with lower affinity (Kd approximately 30 microM) with an average of 0.3 binding sites per molecule. However, less purified HSA, containing globulins, exhibited apparently higher affinity (Kd approximately 8 microM), but lower binding capacity (0.07 sites per molecule) for prazosin. In mixtures of highly purified proteins, the concentrations of AAG, and not HSA, determined the extent and variability of prazosin binding.

Binding of prazosin and propranolol at variable alpha 1-acid glycoprotein and albumin concentrations

1. The effect of variable alpha 1-acid glycoprotein (AAG) and albumin (HSA) concentrations on the binding of prazosin and propranolol was assessed in plasma after surgery and in mixtures of AAG/HSA with concentrations mimicking those found in vivo. 2. On the pre-operative day the binding of prazosin and propranolol was 94.8% and 89.0%, respectively and 97.3% and 93.2%, respectively, 5 days after surgery. 3. In solutions containing mixtures of highly purified AAG and HSA representing the pre-operative state, 88.6% and 83.9% binding of prazosin and propranolol was observed, whereas for solutions mimicking post-operative plasma, the equivalent values were 94.6% and 91.4%, respectively. 4. The ratios between bound and unbound concentrations of both drugs were closely correlated to the concentrations of AAG, but not to the concentrations of HSA. 5. The present study demonstrates that AAG is responsible for the binding variability of prazosin and propranolol in plasma from post-operative patients.

Selectivity in the binding of psychotropic drugs to the variants of alpha-1 acid glycoprotein

The S- and F-forms of alpha-1 acid glycoprotein (AAG) variants have been isolated by isoelectric focusing with immobilines from commercially available AAG. In equilibrium dialysis experiments using a multicompartmental system, a higher affinity for various basic drugs has been found with S- in comparison with F-AAG: Amitriptyline, nortriptyline, imipramine, desipramine, trimipramine, methadone, thioridazine, clomipramine, desmethylclomipramine, and maprotiline. The selectivity (binding to S- vs. F-AAG) is the most pronounced for methadone and the lowest for thioridazine, while it is absent for the acidic drug mephenytoin.