Pharmacokinetic-Pharmacodynamic (PK-PD) Analysis of Second-Line Anti-Tubercular Drugs in Indian Children with Multi-Drug Resistance.

OBJECTIVES: To conduct a thorough pharmacokinetic (PK) - pharmacodynamic (PD) analysis of second-line anti-tubercular therapy (ATT) in children diagnosed with multi-drug resistant tuberculosis (MDR-TB). METHODS: Twenty-seven children undergoing second-line ATT, including kanamycin (KM, n = 13), fluoroquinolones (FQs, n = 26), ethionamide (ETH, n = 20), para amino salicylic acid (PASA, n = 4), and cycloserine (CS, n = 15), were sampled at 0 (pre-dose), 1, 2, 3, and 4 h post-drug administration. Plasma drug levels were determined using a mass spectrometer and the collected dataset underwent non-compartmental PK analysis using PK solver ver2.0. PK/PD assessments involved individual drug simulation studies on 1000 subjects using Modviz Pop ver 1.0 in R-software. RESULTS: A total of 22 and 5 children were considered as responders and non-responders, respectively. Non-compartmental PK analysis revealed mean plasma drug levels of this study cohort attained the targeted maximum drug plasma concentration (Cmax). The ratio of Cmax /minimum inhibitory concentration (MIC) or the area under the curve (AUC)/MIC of the studied drugs had not shown a significant difference between responders and non-responders. Non-responders of ETH and ofloxacin had shown deviation from the derived dose-response profile for the simulated population. CONCLUSIONS: The management of MDR-TB with second-line ATT following national guidelines had cured the majority of the children (> 80%) who participated in the study. Inter-individual variability in few children from the targeted Cmax range suggests the need for future investigations on pharmacogenomic aspects of drug metabolism.

Efficacy of a Novel Antibiotic Drug Combination Toward Multidrug-Resistant Ocular Pathogens.

PURPOSE: Antimicrobial resistance is a global health threat, compounded by the reduction in the discovery of new antibiotics. A repurposed drugs-based approach could provide a viable alternative for the treatment of multidrug-resistant (MDR) bacterial infections. In this study, we sought to evaluate the in vitro efficacy of a novel drug combination, polymyxin B/trimethoprim (PT) + rifampin on MDR isolates from patients with bacterial keratitis in India. METHODS: Forty-three isolates, which included 20 Staphylococcus aureus , 19 Pseudomonas aeruginosa , 3 Pseudomonas stutzeri , and 1 Acinetobacter baumannii , were evaluated for their antibiotic resistance by minimum inhibitory concentration (MIC). Fractional Inhibitory Concentration Index (FICI) testing was performed to measure the antimicrobial impact of PT + rifampin in combination. RESULTS: Among S. aureus isolates, 100% were resistant to at least 1 antibiotic class, 12 (60%) were MDR, and 14 (70%) were classified as methicillin-resistant. Among the gram-negative isolates, >90% were classified as MDR. Fractional Inhibitory Concentration (FIC) testing revealed that PT + rifampin was effective in completely inhibiting growth of all isolates while also displaying additive or synergistic activity in approximately 70% of the strains. Mean FICI values were 0.753 ± 0.311 and 0.791 ± 0.369 for S. aureus and gram-negative isolates, respectively, and a >2-fold reduction in MIC was measured for both PT and rifampin when tested in combination versus alone. CONCLUSIONS: Our data demonstrate the ability of PT + rifampin to eliminate all isolates tested, even those conferring MDR, highlighting the promise of this drug combination for the treatment of bacterial keratitis.

Untargeted metabolomics in the aqueous humor reveals the involvement of TAAR pathway in glaucoma.

Understanding the metabolic dysfunctions and underlying complex pathological mechanisms of neurodegeneration in glaucoma could help discover disease pathways, identify novel biomarkers, and rationalize newer therapeutics. Therefore, we aimed to investigate the local metabolomic alterations in the aqueous humor and plasma of primary glaucomatous patients. This study cohort comprised primary open-angle glaucoma (POAG), primary angle-closure glaucoma (PACG), and cataract control groups. Aqueous humor and plasma samples were collected from patients undergoing trabeculectomy or cataract surgery and subjected to high-resolution mass spectrometry (HRMS) analysis. Spectral information was processed, and the acquired data were subjected to uni-variate as well as multi-variate statistical analyses using MetaboAnalyst ver5.0. To further understand the localized metabolic abnormalities in glaucoma, metabolites affected in aqueous humor were distinguished from metabolites altered in plasma in this study. Nine and twelve metabolites were found to be significantly altered (p < 0.05, variable importance of projection >1 and log2 fold change ≥0.58/≤ -0.58) in the aqueous humor of PACG and POAG patients, respectively. The galactose and amino acid metabolic pathways were locally affected in the PACG and POAG groups, respectively. Based on the observation of the previous findings, gene expression profiles of trace amine-associated receptor-1 (TAAR-1) were studied in rat ocular tissues. The pharmacodynamics of TAAR-1 were explored in rabbits using topical administration of its agonist, ß-phenyl-ethylamine (ß-PEA). TAAR-1 was expressed in the rat's iris-ciliary body, optic nerve, lens, and cornea. ß-PEA elicited a mydriatic response in rabbit eyes, without altering intraocular pressure. Targeted analysis of ß-PEA levels in the aqueous humor of POAG patients showed an insignificant elevation. This study provides new insights regarding alterations in both localized and systemic metabolites in primary glaucomatous patients. This study also demonstrated the propensity of ß-PEA to cause an adrenergic response through the TAAR-1 pathway.

Analysis of the Systemic Exposure of Mitomycin C Used in Glaucoma Filtering Surgery Among Women in the Reproductive Age Group.

PURPOSE: Systemic absorbtion of topically applied mitomycin C (MMC) during trabeculectomy needs to be evaluated to look for any systemic toxicity, which might be a major concern in certain conditions like pregnancy. METHODS: After obtaining ethical committee clearance, female patients in the reproductive age group undergoing trabeculectomy with MMC were included. Pregnant/lactating patients, patients with any systemic illness were excluded. During trabeculectomy, 0.02% MMC was applied subconjunctivally for 2 min and then washed. Blood samples were withdrawn at 1, 2, 4, 8, 12, and 24 hrs after the surgery and analyzed of MMC levels using Liquid chromatography-tandem mass spectroscopy (LC-MS/MS). RESULTS: The mean age of the participants was 29 ± 12 years. MMC was not detected in any of the plasma samples analyzed as it was less than the detection limit (<1.56 ng/mL) of the employed LC-MS/MS assay. CONCLUSION: It can be deduced that the systemic absorption of MMC is negligible or the plasma concentration is less than 1.56 ng/ml (1000 times less than the concentration where systemic toxicity was not observed).

Hydrophilic interaction LC-MS/MS method to avoid endogenous interference in the analysis of 4-hydroxy isoleucine from dietary supplementation of fenugreek.

4-Hydroxy isoleucine is one of the potent hypoglycemic active constituents of fenugreek seeds. A method capable of reducing biological interferences is required for bioavailability studies. An isocratic separation of 4-hydroxy isoleucine from endogenous interferences was achieved in ZIC-cHILIC column using 0.1% formic acid in water and acetonitrile (20:80, % v/v) pumped at 0.5 ml/min. Quantification was performed in multiple reaction monitoring mode using the transitions of m/z 148.1→102.1 and m/z 276.1→142.2 for 4-hydroxy isoleucine and homatropine (as internal standard), respectively. After full method validation, 4-hydroxy isoleucine levels in human plasma and commercial fenugreek formulations were determined. This method showed good linearity in the range of 50-2000 ng/mL. Intra- and interday accuracies were in the range of 90.64-109.0% and precision was <4.82% CV. The mean (SD) plasma concentration of 4-hydroxy isoleucine in healthy individuals at 2 h after oral administration of fenugreek tablet was found to be 1590 (260) ng/mL. Half of marketed formulations were found to contain <0.05% of 4-hydroxy isoleucine content. We developed a rapid hydrophilic interaction liquid chromatography-tandem mass spectrometry method for analysis of 4-hydroxy isoleucine in human plasma. This method can be applied directly to conduct the clinical pharmacokinetics studies of 4-hydroxy isoleucine in human population.

Elevated histamine levels in aqueous humor of patients with glaucoma.

Purpose: Neurotransmitters (NTs) are the key mediators of essential ocular functions, such as processing the visual functions of the retina, maintaining homeostasis of aqueous humor, and regulating ocular blood flow. This study aims to determine variations in the levels of L-glutamate and γ-aminobutyric acid (GABA), histaminergic, adrenergic, cholinergic, and serotonergic NTs in patients with primary glaucoma versus patients with cataract. Methods: This case-control study involved three age-matched groups of patients with primary open angle glaucoma (POAG, n = 14), primary angle closure glaucoma (PACG, n = 21), and cataract (control, n = 19). Patients' aqueous humor and plasma were collected, snap frozen at -80 °C, and subjected to ultrasensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis for quantification of NTs. Results: Baseline intraocular pressure and the cup-to-disc ratio were found to be statistically significantly elevated in the POAG and PACG groups compared to the cataract control group. In aqueous humor, histamine was found to be statistically significantly elevated (5-fold, p<0.0001), whereas 1-methyl histamine was statistically significantly decreased (p<0.05) in POAG compared to the control group. A statistically significant increase in L-glutamate and GABA was observed among both patient groups with glaucoma compared to the cataract control group. Adrenaline was found to be elevated only in the PACG group (2.7-fold, p<0.05). No statistically significant difference was observed among the plasma NT levels between the groups. Conclusions: This study demonstrated the prominent role of the histaminergic system apart from autonomic mechanisms in the progression of glaucoma. Elevated L-glutamate and GABA could be due to retinal ganglionic cell death. Further studies are required to evaluate the effects of histamine on Müller cell dysfunction.

Therapeutic potential of valproic acid in advanced glaucoma: A pilot study.

Purpose: Oral valproic acid (VPA) used as an anticonvulsant has been shown to improve contrast threshold sensitivities in patients receiving it on long-term. This study aimed to evaluate the efficacy of oral VPA in improving visual function in eyes with advanced stage glaucoma. Methods: In this prospective randomized study, 31 patients (n = 31 eyes) with advanced stage glaucoma (with an intraocular pressure <16 mmHg) in at least one eye received oral VPA 500 mg once a day for 3 months and 33 patients (n = 33 eyes) continued on glaucoma therapy. Patients were followed up at 3 and 12 months (to evaluate the legacy effect of the drug). Blood VPA concentrations were measured at 3 months. Following parameters were assessed at baseline, 3 months and 12 months: log of the minimum angle of resolution (LogMAR) visual acuity, mean deviation on visual fields, and multifocal electroretinogram (ERG). Results: Median LogMar visual acuity in the VPA group improved from 0.3 at baseline to 0.18 and 0.18 at 3 and 12 months, respectively (P < 0.01). In comparison, the median visual acuity in control group at baseline was 0.18 and showed neither worsening nor improvement over 3 and 12 months (P = 0.56). The improvement in VPA group was significant compared to the control group (P < 0.01; Wilcoxon Signed-rank test). An improvement in one line was experienced in 11 out of 31 eyes in the VPA group compared to 1 out of 33 eyes among controls (P = 0.003). No significant improvement was noted in the mean deviation, and the multifocal ERG (Latency and amplitudes) in the VPA-treated patients. The average blood VPA concentration measured at 3 months of therapy was 26 ± 8.9 µg/ml (range 8-55 µg/ml) which is much lower than that achieved during anticonvulsant therapy. None of the patients complained of any adverse effects that required stopping VPA therapy. Conclusion: A 3 months oral VPA therapy results in some improvement in visual acuity in a subgroup of eyes with advanced glaucoma and the effect was seen to persist 9 months after the drug was stopped.