A non-extraction HPLC method for the simultaneous determination of serum paracetamol and salicylate

Management of acute paracetamol poisoning in a tertiary care hospital

OBJECTIVES

To compare the management of acute paracetamol poisoning with the best evidence available, and to determine the effect of plasma paracetamol level estimation on the management.

DESIGN

Descriptive study with an intervention.

SETTING

Medical wards of the National Hospital of Sri Lanka, Colombo.

PATIENTS

Patients admitted with a history of acute paracetamol poisoning.

INTERVENTION

Measurement of plasma paracetamol.

METHODS

Data were obtained from the patients, medical staff and medical records. Plasma paracetamol was estimated between 4-24 hours of paracetamol ingestion. The current management practices were compared with the best evidence on acute paracetamol poisoning management.

RESULTS

157 patients were included. The mean ingested dose of paracetamol was 333 mg/kg body weight. Majority of the patients (84%) were transfers. Induced emesis and activated charcoal were given to 91% of patients. N-acetylcysteine was given to 66, methionine to 55, and both to 2. Aclinically important delay in the administration of antidotes was noted; 68% of patients received antidotes after 8 hours of the acute ingestion. Only 31 (26%) had paracetamol levels above the Rumack-Matthew normogram. 74 patients received an antidote despite having a plasma paracetamol level below the toxic level according to the normogram.

INTERPRETATION

Management of acute paracetamol poisoning could be improved by following best available evidence and adapting cheaper methods for plasma paracetamol estimation.

Liquid chromatographic analysis of certain commercial formulations for non-opioid analgesics

A simple and sensitive method for separation and quantitative determination of non-opioid analgesics from pharmaceutical preparations has been developed and validated. Commercial formulations of three non-opioid analgesics, viz. paracetamol, ibuprofen and diclofenac, were chosen for present studies. These were extracted, isolated, purified and recrystallized and were characterized by melting point, lambda(max) and IR. Quantitative determination was carried out using HPLC and TLC supplemented with UV spectrophotometry.

Comparative pharmacokinetics of salicylate in camels, sheep and goats

This study compared some pharmacokinetic parameters of DL-lysine-acetyl salicylate administered intravenously (i.v.) and intramuscularly (i.m.) at a dose of 20 mg/kg in camels, sheep and goats. The data was analyzed using a non-compartmental model. In camels, sheep and goats given the drug i.v., the t1/2 values were 43.1, 31.2 and 27.3; the clearance (Cl) values were 203.7, 261.1, and 280.4 ml/h/kg, while the area under the curve (AUC) were 100.1, 106.9 and 110.5 mg.h/L, respectively. In camels, sheep and goats given the drug by the i.m. route the mean peak plasma concentration (Cmax) were 0.94, 1.44 and 1.74 mg/ml, and the time to reach Cmax (tmax) were 2.94, 2.57 and 2.43h, respectively. The t1/2 values were 48.9, 38.2 and 36.0 min; the clearance (Cl) values were 261.3, 297.4 and 306.4 ml/h/kg, while the area under the curve (AUC) were 101.6, 117.3 and 123.7 mg.h/L, respectively. The drug bioavailability (F) in camels, sheep and goats were 71.3, 78.4 and 79.4% respectively. These findings suggest that the rate of absorption and elimination of the salicylate is slower in camels than in sheep and goats.

Simultaneous determination of methylene violet, halogenated methylene violet and their photoproducts in the presence of DNA by high-performance liquid chromatography using an internal surface reversed-phase column

A simple and rapid isocratic high-performance liquid chromatographic method for the analysis of methylene violet, a neutral phenothiazine dye, in the presence of DNA has been developed. These chromatographic conditions are also applicable to its N-demethylated, bromo and iodo analogs. The method utilizes an internal surface reversed-phase column and a mobile phase consisting of 20% acetonitrile in 50 mM phosphate buffer (pH 7.0) and detection at 280 nm. Under these conditions all five dyes are well resolved from one another and from the faster migrating DNA. The effects of organic modifiers, ionic strength and pH of the buffer on the capacity factors of the dyes have been investigated. The method has successfully been applied to detect the photoproducts of methylene violet and its bromo analog in the presence of DNA without removing the biopolymer from the reaction mixture.

Direct plasma liquid chromatographic-tandem mass spectrometric analysis of granisetron and its 7-hydroxy metabolite utilizing internal surface reversed-phase guard columns and automated column switching devices

An alternative on-line automated sample enrichment technique useful for the direct determination of various drugs and their metabolites in plasma is described for rapid development of highly sensitive and selective liquid chromatographic methods using mass spectrometric detection. The method involves direct injection of plasma onto an internal surface reversed-phase (ISRP) guard column, washing the proteins from the column to waste with aqueous acetonitrile, and backflushing the analytes onto a reversed-phase octyl silica column using switching valves. The analytes were detected using a tandem mass spectrometer operated in selected reaction monitoring (SRM) mode using atmospheric pressure chemical ionization (APCI). Use of two ISRP guard columns in parallel configuration allowed alternate injections of plasma samples on these columns for sample enrichment and shortened the column equilibration and LC-MS-MS analysis times, thereby increasing the sample throughput. The total run time, including both sample enrichment and chromatography, was about 6 min. Using this technique, an analytical method was developed for the quantitation of granisetron and its active 7-hydroxy metabolite in dog plasma. Granisetron is a selective 5-HT3 receptor antagonist used in the prevention and treatment of cytostatic induced nausea and vomiting. Recovery of the analytes was quantitative and the method displayed excellent linearity over the concentration ranges tested. Results from a three day validation study for both compounds demonstrated excellent precision (1.3-8.7%) and accuracy (93-105%) across the calibration range of 0.1 to 50 ng/ml using an 80 microliters plasma sample. The automated method described here was simple, reliable and economical. This on-line approach using ISRP columns and column switching with LC-MS-MS is applicable for the quantification of other pharmaceuticals in pharmacokinetic studies in animals and humans which require high sensitivity.

The pharmacokinetics of salicylate in dairy cattle are not altered by simultaneous intravenous ceftiofur sodium and DL-lysine-acetyl salicylate (aspirin)

This study evaluated potential alterations to the pharmacokinetics of salicylate by concurrently administered ceftiofur sodium. The trial design was a cross-over using 10 non-lactating, non-pregnant dairy cows. In the first period each cow received intravenously (i.v.) 26 mg/kg of DL-lysine acetyl salicylate (aspirin) followed immediately by 2 mg/kg ceftiofur sodium. In the second period each cow received 26 mg/kg of aspirin i.v. Plasma samples were harvested for determination of salicylate concentration by HPLC. The data best fitted a single compartment open model, using weighted non-linear regression. No alterations to the pharmacokinetic parameters of salicylate in cattle by concurrently administered ceftiofur sodium were detected (P < 0.05). Using 90% confidence intervals, and testing for changes of > 20%, control values, elimination half-life (t1/2), apparent volume of distribution (Vd), area under the plasma concentration versus time curve (AUC) and mean residence time (MRT) were not altered. For control animals the elimination rate constant (k(el)) and total body clearance (Cl) were 1.35 +/- 0.43 h-1 and 20.2 +/- 6.1 ml/h.kg respectively (mean +/- SD). Since ceftiofur sodium did not affect the pharmacokinetics of salicylate, dose regimens for aspirin in cattle need not be altered when ceftiofur sodium is administered concurrently.

Evaluation of restricted access media for high-performance liquid chromatographic analysis of sulfonamide antibiotic residues in bovine serum

Three commercially-available high-performance liquid chromatographic columns packed with restricted access media were evaluated for suitability in multi-residue direct injection analysis at the ng/ml level. The internal surface reversed-phase and shielded hydrophobic phase columns were not sufficiently retentive to separate all analytes from the tail of the matrix peak. Coelution of some of the analytes was also observed with these columns. The semi-permeable surface column was significantly more retentive and selective, providing good separation of analyte and matrix peaks. With this column, an analytical protocol requiring no organic solvents was developed for the assay of six sulfonamides at a detection limit of 25 ng/ml.

High-performance liquid chromatography packing materials for the analysis of small molecules in biological matrices by direct injection

The increasing demand on high-performance liquid chromatography to resolve mixtures of closely related components in complex biological matrices in less time with higher precision has led to the development of a variety of new high-performance liquid chromatography columns, which eliminate the need for sample preparation. These packings isolate small molecules from biological macromolecules on direct sample injection by exerting two separation mechanisms. They allow elution of all sample macromolecules with high recovery in one peak at the extraparticulate void, because of size-exclusion interactions with hydrophilic outer particulate surfaces. Simultaneously, these packings allow permeation and partitioning of small molecules on bonded-phases which are protected from contamination by macromolecules. The names given to these new packings include "internal surface reversed-phase", "shielded hydrophobic phase", "semipermeable surface", "dual zone material" and "mixed-functional phases". The fundamental principles behind each of the design concepts are reviewed, and applications are cited.

Mobile phase versus stationary phase approaches to the direct injection of biological fluids in liquid chromatography

The liquid chromatographic analysis of drugs in urine through direct injection without any sample pretreatment was extended to micellar chromatography with nonionic surfactants, the Pinkerton ISRP column and the shielded hydrophobic phase (Hisep) column. The feasibility of using each was demonstrated through the determination of the diuretic, hydrochlorothiazide, in urine. Good separation, recovery, precision and linearity, and adequate limits of detection were obtained for this analysis with all three techniques. The advantages and limitations of the mobile phase approach of micellar chromatography and the two stationary phase approaches are discussed for the direct injection of urine as well as other biological fluids.

Characterization of an internal-surface reversed-phase silica support for liquid chromatography and its application to assays of drugs in serum

Internal-surface reversed-phase (ISRP) silica supports having N-octanoylaminopropyl phases bound to the internal surfaces of the porous silica and N-(2,3-dihydroxypropyl)aminopropyl phases bound to the external surfaces were synthesized from silica particles differing in nominal pore diameters and specific surface areas. These ISRP supports were characterized with regard to physical and chromatographic properties. The support with an N-octanoylaminopropyl phase coverage of 485 mumol/g and an average pore diameter of 65 A was the most suitable for the direct-injection determination of hydrophilic or hydrophobic drugs in serum or plasma. Non-steroidal anti-inflammatory (acetylsalicylic acid and salicylic acid) and tricyclic antidepressant drugs (desipramine and nortriptyline) in serum were successfully determined with this support and an acidic eluent.

Direct serum injection high-performance liquid chromatographic method for the simultaneous determination of phenobarbital, carbamazepine and phenytoin

A method is described for the simultaneous measurement of serum levels of three antiepileptic drugs, phenobarbital, phenytoin and carbamazepine, by direct injection high-performance liquid chromatography on a 25-cm Pinkerton internal surface reversed-phase (ISRP) column. Several commonly available compounds were tested and found not to co-chromatograph with the three drugs of interest or the internal standard, 5-(p-methylphenyl)-5-phenylhydantoin. Results obtained on patients' samples with this method compared well with those from enzyme-multiplied immunoassay technique (EMIT).