Rapid determination of tafenoquine in small volume human plasma samples by high-performance liquid chromatography-tandem mass spectrometry.

A method was developed for the determination of tafenoquine (I) in human plasma using high-performance liquid chromatography-tandem mass spectrometry. Prior to analysis, the protein in plasma samples was precipitated with methanol containing [2H3(15N)]tafenoquine (II) to act as an internal standard. The supernatant was injected onto a Genesis-C18 column without any further clean-up. The mass spectrometer was operated in the positive ion mode, employing a heat assisted nebulisation, electrospray interface. Ions were detected in multiple reaction monitoring mode. The assay required 50 microl of plasma and was precise and accurate within the range 2 to 500 ng/ml. The average within-run and between-run relative standard deviations were < 7% at 2 ng/ml and greater concentrations. The average accuracy of validation standards was generally within +/- 4% of the nominal concentration. There was no evidence of instability of I in human plasma following three complete freeze-thaw cycles and samples can safely be stored for at least 8 months at approximately -70 degrees C. The method was very robust and has been successfully applied to the analysis of clinical samples from patients and healthy volunteers dosed with I.

Automated high-performance liquid chromatography method for the determination of rosiglitazone in human plasma.

A robust, fully automated assay procedure for the determination of rosiglitazone (I, BRL-49653) in human plasma has been developed. Plasma concentrations of I were determined using automated sequential trace enrichment of dialysates (ASTED) coupled to reversed-phase high-performance liquid chromatography. Sequential automated dialysis of human plasma samples was followed by concentration of the dialysate by trace enrichment on a C18 cartridge. Drug and internal standard, SB-204882 (II) were eluted from the trace enrichment cartridge by mobile phase (0.01 M ammonium acetate, pH 8-acetonitrile, 65:35, v/v) onto the HPLC column (a Novapak C18, 4 microm, 100x5 mm radial compression cartridge) protected by a Guard-Pak C18 cartridge. The compounds were detected by fluorescence detection, using an excitation wavelength of 247 nm, and emission wavelength of 367 nm. The lower limit of quantitation of the method was 3 ng/ml (200 microl aliquot) with linearity demonstrated up to 100 ng/ml. Within- and between-run precision and accuracy of determination were better than 10% across the calibration range. There was no evidence of instability of I in human plasma following three complete freeze-thaw cycles and samples can be safely stored for at least 7 months at -20 degrees C. This method has been successfully utilised to provide pharmacokinetic data throughout the clinical development of rosiglitazone.

Rosiglitazone does not alter the pharmacokinetics of metformin.

Rosiglitazone is a potent oral antidiabetic agent of the thiazolidinedione class that works through activation of the peroxisome proliferator-activated nuclear receptor. It improves insulin sensitivity in peripheral tissues and effectively lowers blood glucose in patients with type 2 diabetes. Metformin is a dimethyl-biguanide, also used in type 2 diabetes, that lowers fasting blood glucose primarily by decreasing hepatic glucose output. Rosiglitazone and metformin reduce plasma glucose concentrations via different mechanisms and thus could potentially be used in combination to optimize glycemic control. This study evaluated the effects of the coadministration of these two agents on the pharmacokinetics of both rosiglitazone and metformin. Sixteen male volunteers (22-55 years old) received oral metformin (500 mg every 12 hours), rosiglitazone (2 mg every 12 hours), or the combination each for 4 days. Plasma collected on day 4 of each regimen was assayed for rosiglitazone and metformin concentrations. Oral doses of rosiglitazone and metformin were safe and well tolerated when administered alone or in combination. There were no clinically significant episodes of hypoglycemia or increased blood lactic acid levels following treatment with any regimen. Coadministration of rosiglitazone and metformin had no significant effects on the steady-state pharmacokinetics (AUC(0-12 h), Cmax, tmax, or t1/2) of either drug. The authors conclude that rosiglitazone can be safely administered with metformin and, due to the different mechanisms of action of these agents, may offer a therapeutic advantage in patients with type 2 diabetes mellitus.

Rapid determination of gemifloxacin in human plasma by high-performance liquid chromatography-tandem mass spectrometry.

A method was developed for the determination of gemifloxacin (I) in human plasma using high-performance liquid chromatography-tandem mass spectrometry. Prior to analysis, the protein in plasma samples was precipitated with acetonitrile containing [13C2H3] gemifloxacin (II) to act as an internal standard. The supernatant was injected onto a PLRP-S column without any further clean-up. The mass spectrometer was operated in positive ion mode, employing a heat assisted nebulisation. electrospray interface. Ions were detected in multiple reaction monitoring (MRM) mode. The assay requires 50 microl of plasma and is precise and accurate within the range 10-5,000 ng/ml. The average within-run and between-run coefficients of variation were <11% at 10 ng/ml and greater concentrations. The average accuracy of validation standards was generally within +/-7% of the nominal concentration. There was no evidence of instability of I in human plasma following three complete freeze-thaw cycles and samples can safely be stored for at least 6 months at -20 degrees C. The method proved very robust and was successfully applied to the analysis of clinical samples from patients dosed with gemifloxacin.

Propofol-based anesthesia as compared with standard anesthetic techniques for middle ear surgery.

STUDY OBJECTIVE: To determine if a total intravenous (i.v.) technique with propofol and fentanyl is superior to isoflurane anesthesia in patients undergoing middle ear surgery. DESIGN: Prospective, randomized study. SETTING: Inpatient otolaryngology service at a university medical center. PATIENTS: 102 ASA status I and II nonobese patients with no significant history of diabetes, chronic cholecystitis, neuropathy, or neuromuscular disorders that could produce delayed gastric emptying. INTERVENTIONS: Patients were admitted to the study and randomly divided into three equal groups. I.V. administration of thiopental sodium 5 mg/kg for induction of anesthesia followed by 60% air/oxygen (O2) with isoflurane 1% to 2% end-tidal for maintenance anesthesia (group 1). The same anesthetic was given as above, with the addition of droperidol 25 mcg/kg given after induction (group 2). I.V. administration of propofol 2 mg/kg for induction of anesthesia followed by propofol 50 to 250 mcg/kg/min for maintenance anesthesia. All groups received fentanyl 3 mcg/kg i.v. after induction. MEASUREMENTS AND MAIN RESULTS: Surgical duration, induction, maintenance, and total anesthesia times were recorded in addition to eye opening and extubation. Intergroup comparisons of postoperative nausea, vomiting, and pain were done, as were recovery scores using the Steward system. Patients receiving propofol had significantly less nausea than those receiving isoflurane only (4 of 34 versus 12 of 34, p < 0.05) as well as vomiting (2 of 34 versus 8 of 34, p < 0.05). Immediate recovery scores were significantly better for propofol compared with the isoflurane/droperidol group. Recovery at 30 minutes was also faster with propofol compared with isoflurane or isoflurane/droperidol (5.7 +/- 0.1 min versus 5.1 +/- 0.2 min and 5.2 +/- 0.2 min, p < 0.05). CONCLUSIONS: Propofol-fentanyl seems to be a better anesthetic than isoflurane-fentanyl in reducing the incidence of nausea and vomiting after middle ear surgery. Through the addition of droperidol to the isoflurane anesthetic seemed as effective, emergence from anesthesia was slower. For middle ear surgeries producing emesis, propofol-based anesthetics produced a rapid emergence with less nausea and vomiting.

Metabolic and pharmacokinetic studies following oral administration of famciclovir to the rat and dog.

1. Drug-related material was well absorbed following oral administration of 14C-famciclovir to the male rat at doses up to 4000 mg/kg and to the male dog at doses up to 250 mg/kg, as judged by the early onset of the peak blood or plasma concentrations of radioactivity (usually < or = 1.5h) and the rapid extensive excretion of radioactivity in the urine (57-76 and 86-89% of dose in rat and dog respectively). 2. Famciclovir underwent extensive first-pass metabolism in both species. In rat, following dosing at 40 mg/kg, famciclovir was rapidly and extensively metabolized to the active antiviral compound penciclovir, which reached peak concentrations in the plasma (mean 3.5 micrograms/ml) at 0.5 h. The 6-deoxy precursor of penciclovir, BRL 42359, was the only other major metabolite detected in rat plasma. Cmax values for BRL 42359 (mean 2.2 micrograms/ml) were also achieved at 0.5 h. In dog, extensive conversion of famciclovir to penciclovir, via BRL 42359, also occurred, but its rate of formation from BRL 42359 was somewhat slower than in rat. In dog, following dosing at 25 mg/kg, Cmax values for penciclovir (mean 4.4 micrograms/ml) occurred at 3 h and were lower than the Cmax values for BRL 42359 (mean 10.0 micrograms/ml) which were achieved at 1h. 3. A dose-dependent decrease in the conversion of BRL 42359 to penciclovir occurred in both species, resulting a changes in the ratios of the plasma concentrations of the two metabolites with increasing dose. In rat, the urinary excretion of penciclovir decreased from 36% of dose at 40 mg/kg to 21% at 4000 mg/kg, and was accompanied by a corresponding increase in the urinary excretion of BRL 42359. In dog, a similar decrease in the urinary excretion of penciclovir occurred on increasing the dose of famciclovir from 25 to 250 mg/kg. 4. Penciclovir and BRL 42359 were the major metabolites detected in urine and faeces. In rat, following dosing at 40 mg/kg, 54 and 22% of dose were recovered in the excreta as penciclovir and BRL 42359 respectively. Corresponding recoveries of the two metabolites in the dog were 34 and 50% of dose. The metabolic fate of famciclovir in these animal species is, therefore, similar to that reported previously in man.

Propofol-based anesthesia as compared with standard anesthetic techniques for middle ear surgery.

OBJECTIVE: To determine whether a totally intravenous technique with propofol and fentanyl is superior to isoflurane anesthesia in patients undergoing middle ear surgery. DESIGN: Prospective randomized study. SETTING: Inpatient otolaryngology service at a university medical center. PATIENTS: Physical status 1 and 2 nonobese patients with no significant history of diabetes, chronic cholecystitis, neuropathy, or neuromuscular disorders that could produce delayed gastric emptying. One hundred two patients were admitted to the study and randomly divided into three equal groups. INTERVENTIONS: Intravenous thiopental, 5 mg/kg, was administered for induction of anesthesia followed by 60% air/O2 with isoflurane, 1% to 2% end tidal, for maintenance anesthesia (group 1). The same anesthetic with the addition of droperidol, 25 micrograms/kg, was given after induction (group 2). Propofol, 2 mg/kg, was administered intravenously for induction of anesthesia and followed by propofol, 50 to 250 micrograms/kg/min, for maintenance anesthesia. All groups received fentanyl, 3 micrograms/kg intravenously, after induction. MEASUREMENTS AND MAIN RESULTS: Surgical duration, induction, maintenance, and total anesthesia times were recorded together with eye opening and extubation. Intergroup comparisons of postoperative nausea, vomiting, and pain, and recovery scores, we made by use of the Steward system. Patients receiving propofol, compared with the isoflurane-only group, had significantly less nausea (4/34 vs 12/34 patients, respectively; p < 0.05) and as vomiting (2/34 vs 8/34 patients, respectively; p < 0.05). Immediate recovery scores were significantly better for propofol compared with the isoflurane-droperidol group. Recovery scores at 30 minutes were also faster with propofol compared with isoflurane or isoflurane-droperidol (5.7 +/- 0.1 vs 5.1 +/- 0.2 and 5.2 +/- 0.2; p < 0.05).

Metabolic and pharmacokinetic studies following oral administration of 14C-famciclovir to healthy subjects.

1. Following oral administration of 14C-famciclovir (500 mg) to three healthy male subjects, drug-related material was rapidly absorbed as judged by peak plasma concentrations of radioactive material being achieved by 0.75 h (6.7 +/- 0.9 microgram equiv./ml (mean +/- SD). 2. Famciclovir underwent extensive first-pass metabolism and was only detected in the plasma of one subject at low concentrations (0.5 microgram/ml). Famciclovir was rapidly and extensively metabolized to the active antiviral compound penciclovir, which reached peak concentrations in the plasma of 3.6 +/- 0.7 microgram/ml (0.75 h). The plasma elimination half-life value for penciclovir was 2.1 +/- 0.1 h. The 6-deoxy precursor of penciclovir, BRL 42359, was the only other relatively major metabolite detected in plasma. Peak plasma concentrations of BRL 42359 (1.0 +/- 0.1 microgram/ml) were achieved at 0.5 h. 3. After 3 days, 73.0 +/- 6.1% of the radioactive dose was excreted in urine, showing that good absorption of drug-related material occurred. Renal excretion was rapid since 60.2 +/- 4.2 and 72.3 +/- 5.7% of the dose was recovered in the urine samples collected up to 6 and 24 h, respectively. A good recovery of the administered radioactive dose was obtained since a further 26.6 +/- 5.1% of the dose was excreted in the faeces over a 72-h period. 4. Penciclovir and BRL 42359 were the major metabolites detected in urine and faeces. Penciclovir accounted for 59.2 +/- 4.9 and 4.2 +/- 1.4% of the dose in 0-24 h urine and 0-48 h faeces, respectively. Corresponding values for BRL 42359 were 5.0 +/- 0.5 and 17.0 +/- 6.2%, respectively. These metabolites were identified in the biological samples using hplc-ms and ms-ms with thermospray ionization.

Lack of a pharmacokinetic interaction between oral famciclovir and allopurinol in healthy volunteers.

Famciclovir has been shown to have potent and selective activity against herpesviruses. The possibility of a pharmacokinetic interaction between the anti-viral agent, famciclovir and allopurinol has been investigated in twelve healthy male volunteers following a single oral dose of famciclovir (500 mg) in the presence and absence of steady-state levels of allopurinol (300 mg). Similarly, the pharmacokinetic profiles of allopurinol and oxypurinol prior to and following a single dose of famciclovir were compared. Mean values of Cmax, AUC and terminal-phase half-life for penciclovir following administration of famciclovir alone at 3.3 micrograms.ml-1, 8.8 micrograms.h.ml-1 and 2.1 h, respectively were unchanged by co-administration of allopurinol. Similarly, mean urinary recovery and renal clearance values of penciclovir following famciclovir alone were 56.8% and 27 l.h-1, and when given with allopurinol 59.7% and 27.5 l.h-1, respectively. No evidence of accumulation of the inactive precursor to penciclovir, BRL 42359, was noted as a result of co-administration of the two drugs. Mean steady-state Cmax, AUC and terminal-phase half-life values for allopurinol after co-administration of allopurinol with famciclovir also appeared unchanged from values obtained after dosing of allopurinol alone, at 2.12 micrograms.ml-1, 5.73 micrograms.h.ml-1 and 1.38 h, respectively. Mean Cmax and AUC values of the active metabolite of allopurinol, oxypurinol were 11.2 micrograms.ml-1 and 96.0 micrograms.h.ml-1, respectively, and these were also unaltered by co-administration of famciclovir with allopurinol, with values of 10.6 micrograms/ml and 89.8 micrograms.h/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Linear pharmacokinetics of penciclovir following administration of single oral doses of famciclovir 125, 250, 500 and 750 mg to healthy volunteers.

Twenty healthy male volunteers received single oral doses of famciclovir (125-750 mg), in a randomized, single-blind, crossover study. Plasma and urine concentrations of penciclovir and its 6-deoxy precursor, BRL 42359, were determined and penciclovir plasma concentration-time data submitted to model-independent pharmacokinetic analysis. Peak plasma concentrations of penciclovir were obtained at median times of 0.5-0.75 h after dosing. The areas under the concentration versus time curves (AUC) and the peak penciclovir concentration (Cmax) increased linearly with dose of famciclovir. Time to Cmax, elimination half-life, urinary recovery and renal clearance of penciclovir did not change with increasing dose. Famciclovir was excreted via the kidneys as penciclovir (60%) and BRL 42359 (5%), respectively. Famciclovir was well tolerated by all subjects with a low incidence of adverse effects. In conclusion, penciclovir thus displays linear pharmacokinetics in the anticipated therapeutic dose range of famciclovir.

The tolerance to and pharmacokinetics of penciclovir (BRL 39,123A), a novel antiherpes agent, administered by intravenous infusion to healthy subjects.

The tolerance to and pharmacokinetics of intravenously administered penciclovir (BRL 39,123A), a novel anti-herpes agent, were investigated in 15 healthy male subjects. The volunteers were divided into three groups, receiving either 10, 15 or 20 mg/kg penciclovir by a 60 min constant-rate infusion. Blood samples were taken sequentially up to 48 h after the start of the infusion and urine collections made at appropriate intervals up to 72 h. After a simple solid phase extraction, concentrations of penciclovir in plasma and urine were determined using HPLC with U.V. detection. Mean values of Cmax, corresponding usually with the end of infusion, and of AUC appeared to increase proportionately with dose. Furthermore, there was no evidence that dose significantly affected any individual pharmacokinetic parameter. Penciclovir was distributed into tissues with an overall mean volume of distribution of approximately 1.5 l.kg-1, i.e. approximately double that of body water. It was rapidly eliminated, with a mean total plasma clearance of 39.3 l.h-1, and a mean terminal-phase half-life of 2.0 h. The majority of the dose, approximately 70%, was excreted unchanged in the urine. Mean renal clearance of BRL 39,123 was 28.1 l.h-1, which exceeds normal glomerular filtration rate and approaches renal plasma flow. At all dose-levels, the infusions of penciclovir were well tolerated, with no evidence of drug-related adverse events.

High-performance liquid chromatographic method for the determination of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL-39123) in human plasma and urine.

A rapid, sensitive and reliable reversed-phase high-performance liquid chromatographic (HPLC) method with UV detection has been developed for the assay of a novel anti-herpes agent, 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL-39123), in human plasma and urine. The drug and the internal standard, the structural analogue BRL-42377, were extracted from the biological matrix by adsorption on a cation-exchange column and were subsequently eluted under alkaline conditions prior to HPLC. The method is reproducible, with coefficients of variation of ca. 5%, and linear from 0.1 to at least 30 micrograms ml-1 in plasma and from 50 to at least 2000 micrograms ml-1 in urine. The method has been used extensively to measure BRL-39123 in plasma and urine samples generated during clinical studies and is adequate for defining pharmacokinetics at projected therapeutic doses.

Assessment of the Meditech Euroscanner for clinical use.

In April 1983, Prototype I of the Meditech Whole Body CT Scanner (Euroscanner) was installed at Frenchay Hospital as part of a Department of Health and Social Security (DHSS) trial to assess its function and reliability. After a few months usage, several modifications were made to the machine. The official trial therefore commenced on Prototype II in the middle of January 1984 and lasted until the end of July 1984. During that time a planned changeover took place in the Neuroradiological Department, with the replacement of a ten-year-old EMI 1010 head scanner by an IGE 8800. This meant that from the beginning of May until the end of July, the Meditech Scanner was the only available CT scanner in a busy Regional Department with District Hospital commitments as well. This paper provides a summary of the clinical experiences resulting from the use of the machine, and is a rider to that in which Greensmith et al (1985) describe the physical properties of the machine.

Radiographic appearances of mycoplasma pneumonia.

The chest radiographs of 60 adult patients with serologically proven mycoplasma pneumonia were reviewed. Confluent or patchy consolidation was most commonly seen, and involved one lobe only in 40% of patients. Widespread nodular opacities were seen much less frequently (7%). Pleural fluid was rare. Complete resolution was almost invariable, 40% of radiographs having cleared by four weeks and 96% by eight weeks.