Redefining the established understanding of excitation dynamics of photochromic oxazines.

Since the introduction of photochromic indolo-benzoxazines, difference absorption of these photoexcited compounds has been assigned to the ground state of the ring-opened isomer. This assignment relies on the alleged resemblance of the spectra of photo- and chemically induced forms. In this paper, we expose the issue of the discrepancy between the absorption spectra of photoproducts and the corresponding chemically opened forms. As a result, a substantial change in the current explanation of photodynamics of photochromic oxazines is proposed. The spectral features earlier ascribed to the photoproduct are suggested to arise due to the absorption of the triplet state. This hypothesis was tested and confirmed in acetonitrile by measuring the effect of oxygen quenching of photoproduct states. In view of this interpretation, light-induced ring opening does not occur in indolo-benzoxazines dissolved in acetonitrile, and, consequently these molecules should no longer be regarded as molecular switches. On the other hand, we show that methanol solution under UV light does produce small amounts of ring-opened form of the molecule.

Augmented renal clearance--an evolving risk factor to consider during the treatment with vancomycin.

WHAT IS KNOWN AND OBJECTIVE: Augmented renal clearance (ARC) is a new phenomenon in patients' pathophysiology without universally accepted aetiology and with various incidence rates most often described in critically ill patients in the Intensive Care Unit (ICU). The objective of this retrospective observational comparative study was to estimate the incidence rate of ARC in patients with different medical conditions employing steady state trough vancomycin serum concentrations (VSCss) for analysis. METHODS: All patients tested for VCSss during two years (2010-2011) in a tertiary level hospital were analysed and 77 VSCs were eligible for analysis: 38 (50%) and 39 cases were assigned to the ARC (eCrClCG (creatinine clearance, estimated by Cockcroft-Gault) > 130 mL/min) and the control groups (eCrClCG in the range 90-130 mL/min) respectively. RESULTS AND DISCUSSION: Patients' age, mechanical ventilation and haemodynamically unstable status had significant association with ARC occurrence (P < 0.05). Majority of ARC patients (11 patients (61 %)) were managed in non-ICU settings. ARC event showed statistically significant higher risk for under dosage (RR (relative risk for subtherapeutic VSCss), 1.84; 95% CI, 1.23\x962.74; P = 0.011), and the correlation between different thresholds (eCrClCG >130 mL/min, ≥140 mL/min and ≥150 mL/min) for ARC and VSCss allows to predict decrease of VSCss in case of eCrClCG ≥150 mL/min: every increase of eCrClCG by 40 mL/min predicts clinically relevant decrease of VSCss by 1 mmol/L (1.49 mg/mL). WHAT IS NEW AND CONCLUSION: ARC cases lead to the doubled risk of subtherapeutic VSC, and this phenomenon is a significant event in patients in any hospital department. Investigation of medical patients' status relevant to this phenomenon needs to be continued.