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George Hill

Publications and source records attributed to George Hill.

9 recordsLinked to original sources
PubMed2003

Pharmacokinetics of anti-influenza prodrug oseltamivir in children aged 1-5 years.

OBJECTIVE: The prodrug oseltamivir has been shown to be efficacious and safe for the treatment of influenza for patients 1 year of age or older; however, pharmacokinetic information was lacking for children below 5 years of age. This study was conducted to assess the metabolic and excretory capacity of oseltamivir and its active carboxylate metabolite in young children. METHODS: Twelve healthy children aged 1-5 years received a single oral suspension dose of oseltamivir (45 mg for 3-5 years, 30 mg for 1-2 years). Plasma and urine concentrations of oseltamivir and the carboxylate were determined by means of liquid chromatography/tandem mass spectrometry. RESULTS: Mean peak plasma concentration and area under the plasma concentration-time curve values normalized to milligram per kilogram oseltamivir dose in the 1- to 2-year group are lower than those in the 3- to 5-year group. Mean body weight normalized oral clearance of oseltamivir and its carboxylate in younger subjects aged 1-2 years (259 ml/min/kg and 12.2 ml/min/kg) were, respectively, 52% and 30% higher than those in older subjects aged 3-5 years (170 ml/min/kg and 9.4 ml/min/kg). CONCLUSION: The results demonstrate that infants as young as 1 year old can metabolize and excrete oseltamivir efficiently. The data derived from this study provide the starting dose of oseltamivir for further investigation in an efficacy study among influenza-infected infants less than 1 year of age.

Acetamides↗
PubMed2003

Preparation and characterisation of novel thick sol-gel titania film photocatalysts.

The preparation and characterization of thick (9 microns), clear, mechanically robust and photocatalytically active films of nanocrystalline anatase titania are described. XRD and SEM analysis show the films comprise 13 nm particles of anatase TiO2. Thin (54 nm) films of the 'paste' TiO2, along with sol-gel titania films made by a more traditional route are also prepared and characterised. All titania films mediate the photocatalytic destruction of stearic acid with a quantum yield of 0.0016 +/- 0.0003, using either 365 nm (i.e. BLB) or 254 nm (germicidal) light. P25 TiO2 films also appear to mediate the same process with a similar formal quantum efficiency. Of all the films tested, the thick paste TiO2 films are the most ideally suited for use with near UV light, for reasons which are discussed. All the titania films tested exhibit photoinduced superhydrophilicity.

Journal Article↗
PubMed2002

The anti-influenza drug oseltamivir exhibits low potential to induce pharmacokinetic drug interactions via renal secretion-correlation of in vivo and in vitro studies.

Oseltamivir is an ester prodrug of the active metabolite [3R,4R,5S]-4-acetamido-5-amino-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylate phosphate (Ro 64-0802), a potent and selective inhibitor of neuraminidase enzyme of influenza virus. Oseltamivir is rapidly hydrolyzed by hepatic carboxylesterases to Ro 64-0802, which is then exclusively excreted by glomerular filtration and active tubular secretion without further metabolism. In vivo and in vitro studies were conducted to evaluate the renal drug-drug interaction potential of oseltamivir. Crossover studies were conducted in healthy subjects in which oral oseltamivir was administered alone and coadministered with probenecid, cimetidine, or amoxicillin. Probenecid completely blocked the renal secretion of Ro 64-0802, increasing systemic exposure (area under the curve) by 2.5-fold, but no interaction was observed with cimetidine or amoxicillin. These in vivo data show that Ro 64-0802 is secreted via an organic anion pathway, but Ro 64-0802 does not inhibit amoxicillin renal secretion. In vitro effects of Ro 64-0802 on the human renal organic anionic transporter 1 (hOAT1) were investigated using novel Chinese hamster ovary cells stably transfected with hOAT1. Ro 64-0802 was found to be a low-efficiency substrate for hOAT1 and a very weak inhibitor of hOAT1-mediated transport of p-aminohippuric acid (PAH). Ro 64-0802 did not inhibit the hOAT1-mediated transport of amoxicillin. In contrast, probenecid effectively inhibited the transport of PAH, Ro 64-0802, and amoxicillin via hOAT1. These in vitro observations are consistent with the in vivo data, validating the usefulness of the in vitro system for evaluating such drug-drug interaction. The study results demonstrate that oseltamivir has a low drug-drug interaction potential at the renal tubular level due to inhibition of hOAT1.

Acetamides↗