Exploring the molecular interaction of pheniramine with Enterococcus faecalis homoserine kinase: In-silico studies.

Infections caused by the bacteria Enterococcus faecalis (also known as E. faecalis) are common in hospitals. This bacterium is resistant to a wide range of medicines and causes a variety of nosocomial infections. An increase in the number of infections caused by multidrug-resistant (MDR) bacteria is causing substantial economic and health issues around the world. Consequently, new therapeutic techniques to tackle the growing threat of E. faecalis infections must be developed as soon as possible. In this regard, we have targeted a protein that is regarded to be critical for the survival of bacteria in this experiment. Homoserine kinase (HSK) is a threonine metabolism enzyme that belongs to the GHMP kinase superfamily. It is a crucial enzyme in threonine metabolism. This enzyme is responsible for a critical step in the threonine biosynthesis pathway. Given the important function that E. faecalis Homoserine Kinase (ESK) plays in bacterial metabolism, we report here cloning, expression, purification and structural studies of E. faecalis HSK using homology modelling. In addition, we have reported on the model's molecular docking and Molecular Dynamic Stimulation (MD Stimulation) investigations to validate the results of the docking experiments. The results were promising. In silico investigations came up with the conclusion: pheniramine has good binding affinity for the E. faecalis HSK.

Enantioselective analysis of pheniramine in urine by charged CD-mediated CZE provided with a fiber-based DAD and an on-line sample pretreatment by capillary ITP.

Application potentialities of CZE on-line coupled with capillary ITP and DAD to the identification and determination of trace concentration levels (microg/L) of pheniramine (PHM) enantiomers and their metabolites present in complex ionic matrices of biological origin (urine) are shown. An enhanced (enantio)selectivity of the CZE separation system obtained by the addition of carboxyethyl-beta-CD (CE-beta-CD) to the carrier electrolyte provided CZE conditions for a reliable identification of similar/identical DAD spectra of structurally related compounds (PHM enantiomers and their metabolites) in clinical urine samples differing in qualitative and quantitative composition of sample matrix constituents. A high sample loadability (a 30 microL sample injection volume), partial sample clean-up (removing macroconstituents from the sample), and preconcentration of the analytes in ITP stage resulted in the decrease of concentration LOD for PHM enantiomers in urine to 5.2 and 6.8 microg/L (2.2 x 10(-8) and 2.8 x 10(-8) mol/L), without using any sample pretreatment technique. The background correction and smoothing procedure applied to the raw DAD spectra provided analytically relevant DAD spectra of PHM enantiomers and their metabolites also when they were present in urine sample (30 microL injection volumes of ten-times diluted urine sample) at a 9 x 10(-) (8) mol/L concentration. DAD spectra of PHM enantiomers present in urine samples matched their reference spectra with reasonable certainties. DAD spectra of PHM metabolites were compared with the reference spectra of PHM enantiomers and a good match was found which indicates the similarities in the structures of enantiomers and their metabolites detected in the urine samples. This fact allows performing the quantitative analyses of PHM metabolites in the urine samples by applying the calibration parameters of PHM enantiomers also for PHM metabolites and the results show the possibilities of using the ITP-CZE-DAD combination for the direct analysis of PHM enantiomers and/or their metabolites in urine without any sample pretreatment. ITP-CZE-DAD method with oppositely charged selector is suggested to use in clinical research as it provides favorable performance parameters including sensitivity, linearity, precision, recovery, and robustness with minimal demands on sample preparation.

Fungal transformations of antihistamines: metabolism of brompheniramine, chlorpheniramine, and pheniramine to N-oxide and N-demethylated metabolites by the fungus Cunninghamella elegans.

1. Two strains of the filamentous fungus Cunninghamella elegans (ATCC 9245 and ATCC 36112) were screened for their ability to metabolize three alkylamine-type antihistamines; brompheniramine, chlorpheniramine and pheniramine. 2. Based on the amount of parent drug recovered after 168 h of incubation, C. elegans ATCC 9245 metabolized 60, 45 and 29% of brompheniramine, chlorpheniramine and pheniramine added respectively. The results from strain ATCC 36112 were essentially identical to those of strain ATCC 9245. 3. The metabolic products of N-oxidation and N-demethylation were isolated by reversed-phase hplc and identified by analysing their mass and proton nmr spectra. For all three antihistamines, the mono-N-demethylated metabolite was produced in the greatest amounts. The chloro- and bromo-substituents appeared not to affect the route of metabolism but did influence the relative amounts of metabolites produced. 4. Circular dichroism spectra of the metabolites and the unmetabolized parent antihistamines showed each to be a racemic mixture of the (+) and (-) optical isomers. In addition, comparison of the metabolism of racemic chlorpheniramine to that of optically pure (+) chlorpheniramine showed no significant differences in the ratios of metabolites produced. There was therefore no metabolic stereoselectivity observed by the fungal enzymes.

Pharmacokinetics of pheniramine (Avil) and metabolites in healthy subjects after oral and intravenous administration.

The pharmacokinetics of pheniramine and its two metabolites (N-desmethyl pheniramine and N-didesmethyl pheniramine) were determined in six healthy male subjects after intravenous (n = 3) or oral (n = 3) administration (30.5 mg of pheniramine - free base). Serum and urine levels were measured by HPLC. After i.v. administration, serum concentrations of pheniramine between 231 and 894 ng/ml were reached and after oral administration peak serum concentrations between 173 and 274 ng/ml were reached after 1-2.5 h. AUC values up to 72 h were 3035-4662 (i.v.) and 3507-5768 (ng/ml X h) (oral). The terminal half-lives were estimated to range between 8 and 17 h (i.v.) and 16 and 19 h (oral). Serum levels of the N-desmethyl derivative remained very low (up to 21 ng/ml), but were still detectable after 72 h. Serum levels of the N-didesmethyl derivative were below the detection limit. The amount of pheniramine excreted in the urine for up to 120 h varied between 5.7 and 11.6 mg and 10.2 and 13.2 mg after i.v. and oral administration respectively. Unlike the serum, considerable fractions of the drug occurred as metabolites in urine. Values were 8.1-16.4 mg (i.v.) and 7.4-13.3 mg (oral) for N-desmethyl pheniramine, 0.4-2.9 mg (i.v.) and 0.2-0.8 mg (oral) for N-didesmethyl pheniramine.

Effects of antidepressant drugs on histamine-H1 receptors in the brain.

The histamine-H1 receptor blocking properties of a number of structurally different antidepressant drugs have been evaluated using a 3H-mepyramine binding assay and a guinea-pig ileum preparation. The tricyclic antidepressants all inhibited the histamine-H1 receptor. Some newer antidepressant drugs, such as zimelidine and nomifensine were devoid of activity while others, such as iprindole and mianserin were very potent. It is concluded that antagonistic effects on the histamine-H1 receptor is not associated with the therapeutic efficacy in depression, but may contribute to the sedative effects of the antidepressant drugs.

Reduction of pheniramine toxicity using activated charcoal.

Pheniramine is efficiently adsorbed by Norit Medicinal Activated Charcoal in vitro. Administration of activated charcoal after pheniramine ingestion in dogs resulted in significantly lower blood levels. Norit or another proven effective activated charcoal would be of value in first-aid treatment of pheniramine poisoning.