Richard Prankerd | Monash University (original) (raw)

Papers by Richard Prankerd

International Journal of Pharmaceutics, 1994

The members of a series of 1-alkyloxycarbonyl-5-fluorouracil (5-FU) derivatives have been synthes... more The members of a series of 1-alkyloxycarbonyl-5-fluorouracil (5-FU) derivatives have been synthesized, characterized, and evaluated for their abilities to deliver total 5-FU species into and through skin. The most effective member of the series at delivering 5-FU through skin (flux) was the ethyl derivative, 3 (25 times as effective as 5-FU), which was also the most water soluble member of the series. There was a good correlation between flux and water solubility for the entire series but none between flux and lipid solubility. 3 was also the most effective (4.9 times as effective as 5-FU) member of the series at delivering 5-FU into the skin (Cs), and there was a good correlation between C s and flux except for the hexyl derivative, 6. Although the partition coefficients of the first four members of the 1-alkyloxycarbonyl series were less than those of the corresponding members of the 1-alkylaminocarbonyl series, which were previously studied, their water solubilities were 5-30 times greater and they were 3-10 times more effective at delivering total 5-FU species through hairless mouse skin. However, the 1-alkyloxycarbonyl derivatives delivered mostly intact prodrug (42-90%) through skin while the 1-alkylaminocarbonyl derivatives delivered mostly (> 90%) 5-FU. In spite of this difference, there was a good correlation between permeability coefficients for total 5-FU species delivered and calculated solubility parameters for both series.

Pharmaceutical research, 1993

Single-crystal X-ray diffraction data show that the 3-acetyl group in 1,3-diacetyl-5-FU (FU = flu... more Single-crystal X-ray diffraction data show that the 3-acetyl group in 1,3-diacetyl-5-FU (FU = fluorouracil) is perpendicular to the plane of the 5-FU ring, while the 1-acetyl group is coplanar with the ring. Analyses of 1H NMR and IR spectra provide evidence that the 1- and 3-acyl groups are in different electronic environments, which is consistent with the X-ray diffraction structure. 3-Acetyl-5-FU is thermally unstable, giving mainly 1-acetyl-5-FU (80%) and 5-FU (20%) upon heating. The hydrolysis of 3-acyl derivatives of 5-FU showed a biexponential relationship between in concentration and time which had not been previously observed. The behavior of 3-acetyl-5-FU during hydrolysis can be explained by postulating its initial rapid equilibrium with an intermediate, 2-acetyl-5-FU, which subsequently hydrolyzes to 5-FU or rearranges to 1-acetyl-5-FU, which hydrolyzes to 5-FU. The 2-acetyl intermediate was trapped by its reaction with formaldehyde. The formaldehyde adducts of the symme...

Anaesthesia and intensive care, 2000

Thirty women presenting for major gynaecological oncology surgery under a standardized, combined ... more Thirty women presenting for major gynaecological oncology surgery under a standardized, combined epidural/general anaesthetic technique received either placebo or tenoxicam 20 mg intravenously, in a randomized double-blinded manner prior to surgery. Plasma and urinary electrolytes, creatinine, prostaglandins PgE2 and PgF1 alpha, and thromboxane (TxB2) were collected 12 hours preoperatively and then for four days postoperatively. There were no significant differences in any of the measured parameters between the groups, at any of the measurement times. Mean (SD) creatinine clearance at baseline, 24 h and 48 h was 100.4 (29.7) and 86.9 (27.5), 128.1 (45.9) and 115.0 (40.3), 137.5 (50.7) and 121.6 (38.6) in the placebo and tenoxicam groups respectively (P = 0.28). Both groups required similar amounts of intraoperative ephedrine and intravenous fluids to maintain blood pressure. The minimal changes in plasma and renal parameters reflect predictable responses to major surgery and rehydra...

Anaesthesia and intensive care, 1999

This study examined some pharmacodynamic characteristics of two admixtures of propofol and thiope... more This study examined some pharmacodynamic characteristics of two admixtures of propofol and thiopentone. Ninety unpremedicated ASA 1 or 2 patients were group-randomized to receive, in a double-blinded manner, one of the following mixtures for induction of anaesthesia: Group P50: propofol 1% 10 ml/thiopentone 2.5% 10 ml; Group P75: propofol 1% 15 ml/thiopentone 2.5% 5 ml; Group P100: propofol 1% 20 ml/lignocaine 1% 4 ml. An additional 30 randomized but unblinded patients from the same patient cohort received thiopentone 2.5% to provide predictive dose data for groups P50 and P75. Haemodynamic data were collected pre- and post-induction. The required induction dose of both mixtures of propofol and thiopentone found an additive rather than a synergistic interaction with no significant difference between predicted and observed dose. Thiopentone resulted in significantly more rapid induction of anaesthesia than propofol/lignocaine or propofol/thiopentone. The addition of thiopentone to pr...

American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 1996

The physicochemical compatibility of propofol and thiopental sodium when mixed together in variou... more The physicochemical compatibility of propofol and thiopental sodium when mixed together in various ratios and stored was studied. Mixtures of propofol and thiopental sodium in five volume ratios from 1:3 to 3:1 were refrigerated (4 degrees C) for up to seven days and then centrifuged at 2000g for two hours. Droplet sizes were determined at intervals by optical microscopy and laser diffraction, and chemical stability of the 1:1 mixture was evaluated by high-performance liquid chromatography (HPLC). Optical microscopy and laser diffraction indicated negligible changes in droplet size within 48 hours of mixing. A small increase in the width of the frequency distribution of droplet sizes occurred 24-48 hours after mixing for the two mixtures with the lowest propofol concentration. Some coalescence of droplets occurred on centrifugation. These results indicated negligible formation of droplets that might cause embolism after i.v. injection of fresh mixtures (not more than six hours old)....

We have determined the structure of the reduced form of the DsbA oxidoreductase from Vibrio chole... more We have determined the structure of the reduced form of the DsbA oxidoreductase from Vibrio cholerae. The reduced structure shows a high level of similarity to the crystal structure of the oxidized form and is typical of this class of enzyme containing a thioredoxin domain with an inserted αhelical domain. Proteolytic and thermal stability measurements show that the reduced form of DsbA is considerably more stable than the oxidized form. NMR relaxation data have been collected and analyzed using a model-free approach to probe the dynamics of the reduced and oxidized states of DsbA. Akaike's information criteria have been applied both in the selection of the model-free models and the diffusion tensors that describe the global motions of each redox form. Analysis of the dynamics reveals that the oxidized protein shows increased disorder on the pico-to nanosecond and micro-to millisecond timescale. Many significant changes in dynamics are located either close to the active site or at the insertion points between the domains. In addition, analysis of the diffusion data shows there is a clear difference in the degree of interdomain movement between oxidized and reduced DsbA with the oxidized form being the more rigid. Principal components analysis has been employed to indicate possible concerted movements in the DsbA structure, which suggests that the modeled interdomain motions affect the catalytic cleft of the enzyme. Taken together, these data provide compelling evidence of a role for dynamics in the catalytic cycle of DsbA.

Pharmaceutical research, 2003

Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic aci... more Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic acid, to a (relatively) nonpolar xenobiotic. Although it might be expected that such conjugates may exhibit amphiphilic character (e.g., surface activity and potential to form micelles), no detailed study of the micellization characteristics of any drug-glucuronide conjugates has yet been reported. Therefore, the aim of this study was to investigate the solution behavior and amphiphilic characteristics of gemfibrozil 1-O-beta glucuronide (GG), a model drug-glucuronide conjugate. Crude GG was extracted from the urine of volunteers dosed with 600 mg of gemfibrozil, and this material was then purified by reversed-phase high-performance liquid chromatography to yield a white solid. The amphiphilic properties of GG within the bulk aqueous phase were studied by isothermal titration microcalorimetry and 1H-NMR spectrometry, whereas those at the aqueous/air interface were studied by surface tensiom...

Drug Design and Discovery

N-acetyl-(2), N-caproyl-(3), N-capryl-(4) and N-palmitoyl-pyrazinamide (5) were synthesized by re... more N-acetyl-(2), N-caproyl-(3), N-capryl-(4) and N-palmitoyl-pyrazinamide (5) were synthesized by reacting pyrazinamide (1) with acetic anhydride to prepare (2), or by reacting (1) in chloroform with the corresponding acid chlorides to prepare (3-5). Products were identified by high resolution mass spectroscopy, elemental analysis, and 1H NMR. Melting points, enthalpies of fusion, solubility and octanol-water partition coefficients were determined. Hydrolysis of (2) indicated a pseudo first-order, pH-dependent degradation reaction. Apparent half life times of degradation ranged from 74.2 hours at pH 3 to 5.4 hours at pH 7.34. Derivative (5) was incorporated in liposomes consisting of soy phosphatidylcholine and dipalmitoylphosphatidylglycerol (7:3 molar ratio). The in vitro susceptibility of Mycobacterium avium-intracellulare (MAI) to the liposomal compound containing (5) was tested. MAI was susceptible to (5) at concentrations of 12.5-25 micrograms/ml, although MAI is not susceptible ...

Anaesthesia and intensive care

We have investigated, in a prospective double-blind study, recovery from anaesthesia induced by t... more We have investigated, in a prospective double-blind study, recovery from anaesthesia induced by two admixtures of propofol and thiopentone and compared it with a third group of patients who received propofol and lignocaine. Ninety unpremedicated ASA 1 or 2 patients scheduled for elective gynaecological laparoscopy as a daycase procedure were randomly allocated to receive one of three different mixtures for induction of anaesthesia as part of a standardized anaesthetic: Group P50: propofol 1% 10 ml/thiopentone 2.5% 10 ml, Group P75: propofol 1% 15 ml/thiopentone 2.5% 5 ml, Group P100: propofol 1% 20 ml/lignocaine 1% 4 ml. Recovery from anaesthesia was assessed for up to four hours post-induction by critical flicker fusion threshold and best post-box toy completion time. Comparison was made with preoperative baseline performance. There was no significant difference in postoperative recovery between the three groups with either assessment but no group returned to their mean preoperativ...

Anaesthesia and intensive care

This study compared postoperative analgesic dispensation and measures relating to haemostasis fol... more This study compared postoperative analgesic dispensation and measures relating to haemostasis following intravenous administration, in a randomized double-blinded manner, of either placebo or tenoxicam 20 mg to 30 women presenting for major gynaecological oncology surgery under a standardized, combined epidural/general anaesthetic technique. Pharmacokinetic disposition of tenoxicam in this patient cohort was also described. There was no objective or subjective alteration in haemostatic function or increase in blood loss, nor any deviation from the normal range of values. Postoperative analgesia during the first 48 hours was delivered to achieve a VAS endpoint of less than five on leg-raising, by a combination of a nurse-controlled low-dose background epidural infusion and patient-administered epidural bolus. Greater VAS variability was observed during the first four postoperative hours (P = 0.08). The tenoxicam group self-administered significantly fewer epidural bolus doses to main...

Pharmaceutical Research, 2003

Purpose. Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucu... more Purpose. Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic acid, to a (relatively) nonpolar xenobiotic. Although it might be expected that such conjugates may exhibit amphiphilic character (e.g., surface activity and potential to form micelles), no detailed study of the micellization characteristics of any drug-glucuronide conjugates has yet been reported. Therefore, the aim

Journal of Pharmaceutical Sciences, 2015

The utility of cyclodextrin (CD) complexation in improving apparent solubility of drugs in parent... more The utility of cyclodextrin (CD) complexation in improving apparent solubility of drugs in parenteral formulations is well established. Administration of these formulations delivers CD directly into the systemic circulation, and it may be necessary to demonstrate unaltered in vivo disposition of a drug coadministered with a CD. Crucial to the undertaking of such a study is the need for bioanalytical assays in which CD presence does not impact drug quantitation. This is of particular importance when assessing the potential impact of in vivo CD complexation on the urinary excretion of a drug, as CDs are predominantly eliminated via glomerular filtration, and hence are present in urine at significantly higher concentration than would be present in blood and plasma. Of 23 publications (in the past 30 years) describing preclinical and clinical assessment of drug pharmacokinetics after i.v. administration of CD-enabled formulations, only two reports clearly stated that the presence of CD had no impact on assay performance. In this work, we describe the simple process involved in (1) predicting the maximum concentrations of a modified CD, sulfobutylether7 -β-CD (SBE7 -β-CD), in plasma and urine samples from preclinical studies, and (2) evaluating the impact of SBE7 -β-CD on the quantitative liquid chromatography-mass spectrometry analysis of rimantadine. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1561-1562, 2015.

Journal of pharmaceutical sciences, Jan 8, 2015

Intravenously administered (i.v.) drug-cyclodextrin (CD) inclusion complexes are generally expect... more Intravenously administered (i.v.) drug-cyclodextrin (CD) inclusion complexes are generally expected to dissociate rapidly and completely, such that the i.v. pharmacokinetic profile of a drug is unchanged in the presence of CD. The altered pharmacokinetics of a synthetic ozonide in rats has been attributed to an unusually high-binding affinity (2.3 × 10(6) M(-1) ) between the drug and sulfobutylether7 -β-cyclodextrin (SBE7 -β-CD) with further studies suggesting a significant binding contribution from the adamantane ring. This work investigated the binding affinity of three adamantane derivatives [amantadine (AMA), memantine (MEM) and rimantadine (RIM)] to SBE7 -β-CD and the impact of complexation on their i.v. pharmacokinetics. In vitro studies defined the plasma protein binding, as well as the impact of SBE7 -β-CD on erythrocyte partitioning of each compound. SBE7 -β-CD binding constants for the compounds were within the typical range for drug-like molecules (10(2) -10(4) M(-1) ). T...

The Journal of Physical Chemistry B, 2010

Colistin is an amphiphilic antibiotic that has re-emerged into clinical use due to the increasing... more Colistin is an amphiphilic antibiotic that has re-emerged into clinical use due to the increasing prevalence of difficult-to-treat Gram-negative infections. The existence of self-assembling colloids in solutions of colistin and its derivative prodrug, colistin methanesulfonate (CMS) was investigated. Colistin and CMS reduced the air-water interfacial tension, and dynamic light scattering (DLS) studies showed the existence of 2.07 ± 0.3 nm aggregates above 1.5 mM for colistin, and of 1.98 ± 0.36 nm aggregates for CMS above 3.5 mM (mean ± SD). Above the respective critical micelle concentrations (CMC) the solubility of azithromycin, a hydrophobic antibiotic, increased approximately linearly with increasing surfactant concentration (5:1 mol ratio colistin:azithromycin), suggestive of hydrophobic domains within the micellar cores. Rapid conversion of CMS to colistin occurred below the CMC (60 % over 48 hr), while conversion above the CMC was less than 1 %. The formation of colistin and CMS micelles demonstrated in this study is the proposed mechanism for solubilization of azithromycin and the concentration-dependent stability of CMS.

Protein Expression and Purification, 2005

Rat liver fatty acid binding protein (L-FABP) was eYciently expressed in Escherichia coli and pur... more Rat liver fatty acid binding protein (L-FABP) was eYciently expressed in Escherichia coli and puriWed to homogeneity. The cDNA encoding L-FABP was ligated into the pTrc99A expression vector and expressed by induction with isopropyl--D-thiogalactopyranoside under the control of the P trc promoter. Following an 18 h induction period, L-FABP constituted approximately 3% of the cytosolic protein. The protein could be puriWed to electrophoretic homogeneity (silver-stained polyacrylamide gel detection) by ammonium sulfate fractionation (65% saturation) of the soluble bacterial lysate followed by the chromatographic sequence of anionexchange ! hydrophobic interaction ! anion-exchange chromatography. The recombinant protein displayed an isoelectric point of 7.0 and cross-reactivity with rabbit anti-(human L-FABP) polyclonal antibody. The ligand binding properties of the delipidated L-FABP were examined by titration with the Xuorescent probe 1-anilino-8-naphthalene sulfonic acid and isothermal titration calorimetric analysis of oleic acid binding. The puriWed rat L-FABP displayed a binding stoichiometry of 2:1 (ANS:L-FABP) with dissociation constants (K d ) of 1.7 and 15.5 M for the high and low aYnity binding sites, respectively. The K d values determined by ITC for oleic acid binding were 0.155 and 4.04 M with a binding stoichiometry of approximately 2 mol of fatty acid/mol of protein. These physicochemical and binding properties are in agreement with those of L-FABP isolated from rat liver tissue. 

PLoS ONE, 2013

Oxytocin is recommended by the World Health Organisation as the most effective uterotonic for the... more Oxytocin is recommended by the World Health Organisation as the most effective uterotonic for the prevention and treatment of postpartum haemorrhage. The requirement for parenteral administration by trained healthcare providers and the need for the drug solution to be maintained under cold-chain storage limit the use of oxytocin in the developing world. In this study, a spray-dried ultrafine formulation of oxytocin was developed with an optimal particle size diameter (1-5 µm) to facilitate aerosolised delivery via the lungs. A powder formulation of oxytocin, using mannitol, glycine and leucine as carriers, was prepared with a volume-based median particle diameter of 1.9 µm. Oxytocin content in the formulation was assayed using high-performance liquid chromatography-mass spectroscopy and was found to be unchanged after spray-drying. Ex vivo contractility studies utilising human and ovine uterine tissue indicated no difference in the bioactivity of oxytocin before and after spray-drying. Uterine electromyographic (EMG) activity in postpartum ewes following pulmonary (in vivo) administration of oxytocin closely mimicked that observed immediately postpartum (0-12 h following normal vaginal delivery of the lamb). In comparison to the intramuscular injection, pulmonary administration of an oxytocin dry powder formulation to postpartum ewes resulted in generally similar EMG responses, however a more rapid onset of uterine EMG activity was observed following pulmonary administration (129 ± 18 s) than intramuscular injection (275 ± 22 s). This is the first study to demonstrate the potential for oxytocin to elicit uterine activity after systemic absorption as an aerosolised powder from the lungs. Aerosolised oxytocin has the potential to provide a stable and easy to administer delivery system for effective prevention and treatment of postpartum haemorrhage in resource-poor settings in the developing world.

International Journal of Pharmaceutics, 1994

The members of a series of 1-alkyloxycarbonyl-5-fluorouracil (5-FU) derivatives have been synthes... more The members of a series of 1-alkyloxycarbonyl-5-fluorouracil (5-FU) derivatives have been synthesized, characterized, and evaluated for their abilities to deliver total 5-FU species into and through skin. The most effective member of the series at delivering 5-FU through skin (flux) was the ethyl derivative, 3 (25 times as effective as 5-FU), which was also the most water soluble member of the series. There was a good correlation between flux and water solubility for the entire series but none between flux and lipid solubility. 3 was also the most effective (4.9 times as effective as 5-FU) member of the series at delivering 5-FU into the skin (Cs), and there was a good correlation between C s and flux except for the hexyl derivative, 6. Although the partition coefficients of the first four members of the 1-alkyloxycarbonyl series were less than those of the corresponding members of the 1-alkylaminocarbonyl series, which were previously studied, their water solubilities were 5-30 times greater and they were 3-10 times more effective at delivering total 5-FU species through hairless mouse skin. However, the 1-alkyloxycarbonyl derivatives delivered mostly intact prodrug (42-90%) through skin while the 1-alkylaminocarbonyl derivatives delivered mostly (> 90%) 5-FU. In spite of this difference, there was a good correlation between permeability coefficients for total 5-FU species delivered and calculated solubility parameters for both series.

Pharmaceutical research, 1993

Single-crystal X-ray diffraction data show that the 3-acetyl group in 1,3-diacetyl-5-FU (FU = flu... more Single-crystal X-ray diffraction data show that the 3-acetyl group in 1,3-diacetyl-5-FU (FU = fluorouracil) is perpendicular to the plane of the 5-FU ring, while the 1-acetyl group is coplanar with the ring. Analyses of 1H NMR and IR spectra provide evidence that the 1- and 3-acyl groups are in different electronic environments, which is consistent with the X-ray diffraction structure. 3-Acetyl-5-FU is thermally unstable, giving mainly 1-acetyl-5-FU (80%) and 5-FU (20%) upon heating. The hydrolysis of 3-acyl derivatives of 5-FU showed a biexponential relationship between in concentration and time which had not been previously observed. The behavior of 3-acetyl-5-FU during hydrolysis can be explained by postulating its initial rapid equilibrium with an intermediate, 2-acetyl-5-FU, which subsequently hydrolyzes to 5-FU or rearranges to 1-acetyl-5-FU, which hydrolyzes to 5-FU. The 2-acetyl intermediate was trapped by its reaction with formaldehyde. The formaldehyde adducts of the symme...

Anaesthesia and intensive care, 2000

Thirty women presenting for major gynaecological oncology surgery under a standardized, combined ... more Thirty women presenting for major gynaecological oncology surgery under a standardized, combined epidural/general anaesthetic technique received either placebo or tenoxicam 20 mg intravenously, in a randomized double-blinded manner prior to surgery. Plasma and urinary electrolytes, creatinine, prostaglandins PgE2 and PgF1 alpha, and thromboxane (TxB2) were collected 12 hours preoperatively and then for four days postoperatively. There were no significant differences in any of the measured parameters between the groups, at any of the measurement times. Mean (SD) creatinine clearance at baseline, 24 h and 48 h was 100.4 (29.7) and 86.9 (27.5), 128.1 (45.9) and 115.0 (40.3), 137.5 (50.7) and 121.6 (38.6) in the placebo and tenoxicam groups respectively (P = 0.28). Both groups required similar amounts of intraoperative ephedrine and intravenous fluids to maintain blood pressure. The minimal changes in plasma and renal parameters reflect predictable responses to major surgery and rehydra...

Anaesthesia and intensive care, 1999

This study examined some pharmacodynamic characteristics of two admixtures of propofol and thiope... more This study examined some pharmacodynamic characteristics of two admixtures of propofol and thiopentone. Ninety unpremedicated ASA 1 or 2 patients were group-randomized to receive, in a double-blinded manner, one of the following mixtures for induction of anaesthesia: Group P50: propofol 1% 10 ml/thiopentone 2.5% 10 ml; Group P75: propofol 1% 15 ml/thiopentone 2.5% 5 ml; Group P100: propofol 1% 20 ml/lignocaine 1% 4 ml. An additional 30 randomized but unblinded patients from the same patient cohort received thiopentone 2.5% to provide predictive dose data for groups P50 and P75. Haemodynamic data were collected pre- and post-induction. The required induction dose of both mixtures of propofol and thiopentone found an additive rather than a synergistic interaction with no significant difference between predicted and observed dose. Thiopentone resulted in significantly more rapid induction of anaesthesia than propofol/lignocaine or propofol/thiopentone. The addition of thiopentone to pr...

American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 1996

The physicochemical compatibility of propofol and thiopental sodium when mixed together in variou... more The physicochemical compatibility of propofol and thiopental sodium when mixed together in various ratios and stored was studied. Mixtures of propofol and thiopental sodium in five volume ratios from 1:3 to 3:1 were refrigerated (4 degrees C) for up to seven days and then centrifuged at 2000g for two hours. Droplet sizes were determined at intervals by optical microscopy and laser diffraction, and chemical stability of the 1:1 mixture was evaluated by high-performance liquid chromatography (HPLC). Optical microscopy and laser diffraction indicated negligible changes in droplet size within 48 hours of mixing. A small increase in the width of the frequency distribution of droplet sizes occurred 24-48 hours after mixing for the two mixtures with the lowest propofol concentration. Some coalescence of droplets occurred on centrifugation. These results indicated negligible formation of droplets that might cause embolism after i.v. injection of fresh mixtures (not more than six hours old)....

We have determined the structure of the reduced form of the DsbA oxidoreductase from Vibrio chole... more We have determined the structure of the reduced form of the DsbA oxidoreductase from Vibrio cholerae. The reduced structure shows a high level of similarity to the crystal structure of the oxidized form and is typical of this class of enzyme containing a thioredoxin domain with an inserted αhelical domain. Proteolytic and thermal stability measurements show that the reduced form of DsbA is considerably more stable than the oxidized form. NMR relaxation data have been collected and analyzed using a model-free approach to probe the dynamics of the reduced and oxidized states of DsbA. Akaike's information criteria have been applied both in the selection of the model-free models and the diffusion tensors that describe the global motions of each redox form. Analysis of the dynamics reveals that the oxidized protein shows increased disorder on the pico-to nanosecond and micro-to millisecond timescale. Many significant changes in dynamics are located either close to the active site or at the insertion points between the domains. In addition, analysis of the diffusion data shows there is a clear difference in the degree of interdomain movement between oxidized and reduced DsbA with the oxidized form being the more rigid. Principal components analysis has been employed to indicate possible concerted movements in the DsbA structure, which suggests that the modeled interdomain motions affect the catalytic cleft of the enzyme. Taken together, these data provide compelling evidence of a role for dynamics in the catalytic cycle of DsbA.

Pharmaceutical research, 2003

Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic aci... more Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic acid, to a (relatively) nonpolar xenobiotic. Although it might be expected that such conjugates may exhibit amphiphilic character (e.g., surface activity and potential to form micelles), no detailed study of the micellization characteristics of any drug-glucuronide conjugates has yet been reported. Therefore, the aim of this study was to investigate the solution behavior and amphiphilic characteristics of gemfibrozil 1-O-beta glucuronide (GG), a model drug-glucuronide conjugate. Crude GG was extracted from the urine of volunteers dosed with 600 mg of gemfibrozil, and this material was then purified by reversed-phase high-performance liquid chromatography to yield a white solid. The amphiphilic properties of GG within the bulk aqueous phase were studied by isothermal titration microcalorimetry and 1H-NMR spectrometry, whereas those at the aqueous/air interface were studied by surface tensiom...

Drug Design and Discovery

N-acetyl-(2), N-caproyl-(3), N-capryl-(4) and N-palmitoyl-pyrazinamide (5) were synthesized by re... more N-acetyl-(2), N-caproyl-(3), N-capryl-(4) and N-palmitoyl-pyrazinamide (5) were synthesized by reacting pyrazinamide (1) with acetic anhydride to prepare (2), or by reacting (1) in chloroform with the corresponding acid chlorides to prepare (3-5). Products were identified by high resolution mass spectroscopy, elemental analysis, and 1H NMR. Melting points, enthalpies of fusion, solubility and octanol-water partition coefficients were determined. Hydrolysis of (2) indicated a pseudo first-order, pH-dependent degradation reaction. Apparent half life times of degradation ranged from 74.2 hours at pH 3 to 5.4 hours at pH 7.34. Derivative (5) was incorporated in liposomes consisting of soy phosphatidylcholine and dipalmitoylphosphatidylglycerol (7:3 molar ratio). The in vitro susceptibility of Mycobacterium avium-intracellulare (MAI) to the liposomal compound containing (5) was tested. MAI was susceptible to (5) at concentrations of 12.5-25 micrograms/ml, although MAI is not susceptible ...

Anaesthesia and intensive care

We have investigated, in a prospective double-blind study, recovery from anaesthesia induced by t... more We have investigated, in a prospective double-blind study, recovery from anaesthesia induced by two admixtures of propofol and thiopentone and compared it with a third group of patients who received propofol and lignocaine. Ninety unpremedicated ASA 1 or 2 patients scheduled for elective gynaecological laparoscopy as a daycase procedure were randomly allocated to receive one of three different mixtures for induction of anaesthesia as part of a standardized anaesthetic: Group P50: propofol 1% 10 ml/thiopentone 2.5% 10 ml, Group P75: propofol 1% 15 ml/thiopentone 2.5% 5 ml, Group P100: propofol 1% 20 ml/lignocaine 1% 4 ml. Recovery from anaesthesia was assessed for up to four hours post-induction by critical flicker fusion threshold and best post-box toy completion time. Comparison was made with preoperative baseline performance. There was no significant difference in postoperative recovery between the three groups with either assessment but no group returned to their mean preoperativ...

Anaesthesia and intensive care

This study compared postoperative analgesic dispensation and measures relating to haemostasis fol... more This study compared postoperative analgesic dispensation and measures relating to haemostasis following intravenous administration, in a randomized double-blinded manner, of either placebo or tenoxicam 20 mg to 30 women presenting for major gynaecological oncology surgery under a standardized, combined epidural/general anaesthetic technique. Pharmacokinetic disposition of tenoxicam in this patient cohort was also described. There was no objective or subjective alteration in haemostatic function or increase in blood loss, nor any deviation from the normal range of values. Postoperative analgesia during the first 48 hours was delivered to achieve a VAS endpoint of less than five on leg-raising, by a combination of a nurse-controlled low-dose background epidural infusion and patient-administered epidural bolus. Greater VAS variability was observed during the first four postoperative hours (P = 0.08). The tenoxicam group self-administered significantly fewer epidural bolus doses to main...

Pharmaceutical Research, 2003

Purpose. Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucu... more Purpose. Phase II metabolism involves the conjugation of a polar moiety, such as sulfate or glucuronic acid, to a (relatively) nonpolar xenobiotic. Although it might be expected that such conjugates may exhibit amphiphilic character (e.g., surface activity and potential to form micelles), no detailed study of the micellization characteristics of any drug-glucuronide conjugates has yet been reported. Therefore, the aim

Journal of Pharmaceutical Sciences, 2015

The utility of cyclodextrin (CD) complexation in improving apparent solubility of drugs in parent... more The utility of cyclodextrin (CD) complexation in improving apparent solubility of drugs in parenteral formulations is well established. Administration of these formulations delivers CD directly into the systemic circulation, and it may be necessary to demonstrate unaltered in vivo disposition of a drug coadministered with a CD. Crucial to the undertaking of such a study is the need for bioanalytical assays in which CD presence does not impact drug quantitation. This is of particular importance when assessing the potential impact of in vivo CD complexation on the urinary excretion of a drug, as CDs are predominantly eliminated via glomerular filtration, and hence are present in urine at significantly higher concentration than would be present in blood and plasma. Of 23 publications (in the past 30 years) describing preclinical and clinical assessment of drug pharmacokinetics after i.v. administration of CD-enabled formulations, only two reports clearly stated that the presence of CD had no impact on assay performance. In this work, we describe the simple process involved in (1) predicting the maximum concentrations of a modified CD, sulfobutylether7 -β-CD (SBE7 -β-CD), in plasma and urine samples from preclinical studies, and (2) evaluating the impact of SBE7 -β-CD on the quantitative liquid chromatography-mass spectrometry analysis of rimantadine. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:1561-1562, 2015.

Journal of pharmaceutical sciences, Jan 8, 2015

Intravenously administered (i.v.) drug-cyclodextrin (CD) inclusion complexes are generally expect... more Intravenously administered (i.v.) drug-cyclodextrin (CD) inclusion complexes are generally expected to dissociate rapidly and completely, such that the i.v. pharmacokinetic profile of a drug is unchanged in the presence of CD. The altered pharmacokinetics of a synthetic ozonide in rats has been attributed to an unusually high-binding affinity (2.3 × 10(6) M(-1) ) between the drug and sulfobutylether7 -β-cyclodextrin (SBE7 -β-CD) with further studies suggesting a significant binding contribution from the adamantane ring. This work investigated the binding affinity of three adamantane derivatives [amantadine (AMA), memantine (MEM) and rimantadine (RIM)] to SBE7 -β-CD and the impact of complexation on their i.v. pharmacokinetics. In vitro studies defined the plasma protein binding, as well as the impact of SBE7 -β-CD on erythrocyte partitioning of each compound. SBE7 -β-CD binding constants for the compounds were within the typical range for drug-like molecules (10(2) -10(4) M(-1) ). T...

The Journal of Physical Chemistry B, 2010

Colistin is an amphiphilic antibiotic that has re-emerged into clinical use due to the increasing... more Colistin is an amphiphilic antibiotic that has re-emerged into clinical use due to the increasing prevalence of difficult-to-treat Gram-negative infections. The existence of self-assembling colloids in solutions of colistin and its derivative prodrug, colistin methanesulfonate (CMS) was investigated. Colistin and CMS reduced the air-water interfacial tension, and dynamic light scattering (DLS) studies showed the existence of 2.07 ± 0.3 nm aggregates above 1.5 mM for colistin, and of 1.98 ± 0.36 nm aggregates for CMS above 3.5 mM (mean ± SD). Above the respective critical micelle concentrations (CMC) the solubility of azithromycin, a hydrophobic antibiotic, increased approximately linearly with increasing surfactant concentration (5:1 mol ratio colistin:azithromycin), suggestive of hydrophobic domains within the micellar cores. Rapid conversion of CMS to colistin occurred below the CMC (60 % over 48 hr), while conversion above the CMC was less than 1 %. The formation of colistin and CMS micelles demonstrated in this study is the proposed mechanism for solubilization of azithromycin and the concentration-dependent stability of CMS.

Protein Expression and Purification, 2005

Rat liver fatty acid binding protein (L-FABP) was eYciently expressed in Escherichia coli and pur... more Rat liver fatty acid binding protein (L-FABP) was eYciently expressed in Escherichia coli and puriWed to homogeneity. The cDNA encoding L-FABP was ligated into the pTrc99A expression vector and expressed by induction with isopropyl--D-thiogalactopyranoside under the control of the P trc promoter. Following an 18 h induction period, L-FABP constituted approximately 3% of the cytosolic protein. The protein could be puriWed to electrophoretic homogeneity (silver-stained polyacrylamide gel detection) by ammonium sulfate fractionation (65% saturation) of the soluble bacterial lysate followed by the chromatographic sequence of anionexchange ! hydrophobic interaction ! anion-exchange chromatography. The recombinant protein displayed an isoelectric point of 7.0 and cross-reactivity with rabbit anti-(human L-FABP) polyclonal antibody. The ligand binding properties of the delipidated L-FABP were examined by titration with the Xuorescent probe 1-anilino-8-naphthalene sulfonic acid and isothermal titration calorimetric analysis of oleic acid binding. The puriWed rat L-FABP displayed a binding stoichiometry of 2:1 (ANS:L-FABP) with dissociation constants (K d ) of 1.7 and 15.5 M for the high and low aYnity binding sites, respectively. The K d values determined by ITC for oleic acid binding were 0.155 and 4.04 M with a binding stoichiometry of approximately 2 mol of fatty acid/mol of protein. These physicochemical and binding properties are in agreement with those of L-FABP isolated from rat liver tissue. 

PLoS ONE, 2013

Oxytocin is recommended by the World Health Organisation as the most effective uterotonic for the... more Oxytocin is recommended by the World Health Organisation as the most effective uterotonic for the prevention and treatment of postpartum haemorrhage. The requirement for parenteral administration by trained healthcare providers and the need for the drug solution to be maintained under cold-chain storage limit the use of oxytocin in the developing world. In this study, a spray-dried ultrafine formulation of oxytocin was developed with an optimal particle size diameter (1-5 µm) to facilitate aerosolised delivery via the lungs. A powder formulation of oxytocin, using mannitol, glycine and leucine as carriers, was prepared with a volume-based median particle diameter of 1.9 µm. Oxytocin content in the formulation was assayed using high-performance liquid chromatography-mass spectroscopy and was found to be unchanged after spray-drying. Ex vivo contractility studies utilising human and ovine uterine tissue indicated no difference in the bioactivity of oxytocin before and after spray-drying. Uterine electromyographic (EMG) activity in postpartum ewes following pulmonary (in vivo) administration of oxytocin closely mimicked that observed immediately postpartum (0-12 h following normal vaginal delivery of the lamb). In comparison to the intramuscular injection, pulmonary administration of an oxytocin dry powder formulation to postpartum ewes resulted in generally similar EMG responses, however a more rapid onset of uterine EMG activity was observed following pulmonary administration (129 ± 18 s) than intramuscular injection (275 ± 22 s). This is the first study to demonstrate the potential for oxytocin to elicit uterine activity after systemic absorption as an aerosolised powder from the lungs. Aerosolised oxytocin has the potential to provide a stable and easy to administer delivery system for effective prevention and treatment of postpartum haemorrhage in resource-poor settings in the developing world.