Molecular lipophilicity determination of a huperzine series by HPLC: comparison of C18 and IAM stationary phases.

Two hydrophobic parameters (logkw-C18 and logkw-IAM, respectively) of a huperzine A series were extrapolated by high performance liquid chromatography (HPLC) using both C18 and immobilised artificial membrane (IAM) columns. A mathematical correlation between C18 and IAM hydrophobic parameters was completed, suggesting a similar behaviour on both columns. This behaviour was principally led by hydrophobic forces. The theoretical lipophilicity (logP) of each compound was computed using Pallas software and compared to experimental values, showing a similar lipophilic behaviour. Finally, the huperzine logkw-IAM and logkw-C18 values were correlated with the relative bound percentage of huperzine in human serum albumin, confirming that hydrophobic forces are predominant in the huperzine-HSA binding mechanism.

Development of a rapid RP-HPLC method for the determination of clonazepam in human plasma.

A rapid and sensitive high-performance liquid chromatography method with UV detection was developed for the determination of clonazepam in human plasma using 3-methylclonazepam, as internal standard. A one-step extraction of both compounds was performed with a mixture of hexane/ethyl acetate (90:10, v/v). The HPLC analysis was carried out on a Nova Pak((R)) C(18) reversed-phase column with a mobile phase of acetonitrile-0.01 M sodium acetate adjusted to pH 7 with dilute acetic acid (40:60, v/v). A linear response was observed over the concentration range 5-100 ng/mL. Intra- and inter-day assay precision and accuracy fulfilled the international requirements. The lower limit of quantification was 5 ng/mL without interference of endogenous components. For analytical purpose, the stability of clonazepam in bidistilled water and plasma has been studied. A rapid degradation was noticed when clonazepam was stored in bidistilled water at the daylight following a first-order kinetic rate with a 87 min half life whereas no significant degradation was observed in plasma. This method was applied to measure plasma concentrations of clonazepam either in patients receiving therapeutic doses or in poisoning cases.

Comparison of patient questionnaires and plasma assays in intentional drug overdoses.

Our aim was to explore the agreement between clinically collected information on purported drug intake and plasma data in intentional drug overdose. We included all subjects with intentional drug overdose above 15 years of age consecutively admitted to the Emergency Department of the University Hospital during 4 months. Information about drugs used and sources of this information was collected and compared to presence of drug in plasma, concerning four drugs with high toxic potential (tricyclic antidepressants, meprobamate, paracetamol and ethanol). Sensitivity, specificity, predictive positive and negative values of all sources of information pooled were assessed for each drug. 413 intentional drug overdoses were included, 66% with more than one drug. According to clinical information, 8% took tricyclic antidepressants, 11% meprobamate, 9% paracetamol and 41% ethanol. Systematic plasma assays confirmed this in 59% of cases for tricyclic antidepressants, 76% for meprobamate and ethanol, and 77% for paracetamol. Plasma concentrations were considered toxic in 28% of cases for tricyclic antidepressants, 65% for meprobamate, 43% for ethanol and never for paracetamol. Tricyclic antidepressants and meprobamate were found unexpectedly in 3%, paracetamol in 7% and ethanol in 6%. Toxic concentrations were found only with meprobamate. The risk of erroneous, clinically collected information was greater by excess (25 to 40% false positives) than by lack (3 to 7% false negatives). Thus, the consequences of erroneous, clinically collected information were probably more excess cost for the institution than medical risk for the patients. However these results found at the population level may not be true at an individual level.

A simple high-performance liquid chromatographic method for detection of hydroxyzine in human plasma after overdose.

INTRODUCTION: Hydroxyzine, a piperazine H1-receptor antagonist, is effective in generalised anxiety disorder. For toxicological purposes, a simple reversed-phase high-performance liquid chromatographic assay was developed for the detection of hydroxyzine in human plasma. METHODS: A liquid-liquid procedure was used to extract the drug from plasma in the presence of an internal standard (clothiapine). The analysis was performed on a Spherisorb S5 C(8) analytical column with UV detection. RESULTS: A linear response was observed over the concentration range 20-1500 ng/ml. A good accuracy (bias<7.3%) was achieved for all quality controls, with intraday and interday variation coefficients inferior to 8.5%. The limit of detection was 10 ng/ml, without interference of endogenous components. DISCUSSION: This rapid method (run time<13 min) is currently used for poison management involving hydroxyzine.

Synthesis, antimalarial activity, and molecular modeling of new pyrrolo[1,2-a]quinoxalines, bispyrrolo[1,2-a]quinoxalines, bispyrido[3,2-e]pyrrolo[1,2-a]pyrazines, and bispyrrolo[1,2-a]thieno[3,2-e]pyrazines.

Three pyrrolo[1,2-a]quinoxalines, 15 bispyrrolo[1,2-a]quinoxalines, bispyrido[3,2-e]pyrrolo[1,2-a]pyrazines, and bispyrrolo[1,2-a]thieno[3,2-e]pyrazines were synthesized from various substituted nitroanilines or nitropyridines and tested for their in vitro activity upon the erythrocytic development of Plasmodium falciparum strains with different chloroquine-resistance status. Bispyrrolo[1,2-a]quinoxalines showed superior antimalarial activity with respect to monopyrrolo[1,2-a]quinoxalines. The best activity was observed with bispyrrolo[1,2-a]quinoxalines linked by a bis(3-aminopropyl)piperazine. Moreover, it was observed that the presence of a methoxy group on the pyrrolo[1,2-a]quinoxaline nucleus increased the pharmacological activity. Drug effects upon beta-hematin formation were assayed and showed similar or higher inhibitory activities than CQ. A possible mechanism of interaction implicating binding of pyrroloquinoxalines to beta-hematin was supported by molecular modeling.

Diffusion of arylpropionate non-steroidal anti-inflammatory drugs into the cerebrospinal fluid: a quantitative structure-activity relationship approach.

A quantitative structure-activity relationship (QSAR) analysis of a series of arylpropionic acid non-steroidal anti-inflammatory drugs (NSAIDs) has been performed to determine which physicochemical properties of these compounds are involved in their diffusion into the cerebrospinal fluid (CSF). The penetration of eight arylpropionic acid derivatives into CSF was studied in male Wistar rats. After intraperitoneal administration of each compound (5 mg/kg), blood and CSF samples were collected at different times (0.5, 1, 3 and 6 h). The fraction unbound to plasma protein was determined using ultrafiltration. The areas under the curve of the free plasma (AUCF) and CSF (AUCCSF) concentrations were calculated according to the trapezoidal rule. The overall drug transit into CSF was estimated by the ratio RAUC (AUCCSF : AUCF). The lipophilicity was expressed as the chromatographic capacity factor (log kIAM) determined by high-performance liquid chromatography on an immobilized artificial membrane (IAM) column. A significant parabolic relationship was sought between lipophilicity (log kIAM) and the capacity of diffusion across the blood-brain barrier (log RAUC) (r = 0.928; P < 0.01). The arylpropionic acid NSAIDs exhibiting a lipophilicity value between 1.1 and 1.7 entered the CSF easily (RAUC > 1). The molecular weight (MW) was included in this parabolic relationship by means of a multiple regression analysis. This physicochemical parameter improved the correlation (r = 0.976; P < 0.005). Based on our findings, diffusion of arylpropionic acid NSAIDs into CSF appears to depend primarily on their lipophilicity and MW.

Potential of immobilized artificial membrane chromatography for lipophilicity determination of arylpropionic acid non-steroidal anti-inflammatory drugs.

Molecular lipophilicity can be expressed by logP or more conveniently by logk, i.e. determined by the traditional shake-flask technique or by liquid chromatography. The logk of 11 arylpropionic non-steroidal anti-inflammatory drugs (NSAIDs) was determined at pH 7.4 of the eluent using two stationary phases i.e. octadecylsilane phase and an immobilized artificial membrane (IAM.PC.MG) packing. The chromatographic retention factors extrapolated to 100% aqueous phase (logk(wODS) and logk(wIAM)) were correlated with n-octanol/water lipophilicity parameters (logP) and with n-octanol/water partition coefficients corrected for ionization at pH 7.4 (logD7.4). In this series of compounds, significant linear correlations (r>0.94) between the chromatographic parameters (logk(wIAM)) and the reference lipophilicity data (logP and logD7.4) were described. Moreover, regression analysis between the lipophilicity parameters and some pharmacokinetic data for the drugs under study were performed. The logk(wIAM) parameter over n-octanol/water partition data seems to provide a good model to obtain lipophilicity parameters of arylpropionic acid NSAIDs for quantitative structure-activity relationships studies.

High-performance liquid chromatographic method with diode array detection for identification and quantification of the eight new antidepressants and five of their active metabolites in plasma after overdose.

A high-performance liquid chromatographic method is described for the determination of selective serotonin reuptake inhibitors (fluvoxamine, paroxetine, sertraline, fluoxetine, citalopram, mirtazapine), serotonin norepinephrine reuptake inhibitors (milnacipram, venlafaxine), a noradrenergic and specific serotoninergic antidepressant (mirtazapine), and five pharmacologically active metabolites (desmethylcitalopram, didesmethylcitalopram, norfluoxetine, O-desmethylvenlafaxine, desmethylmirtazapine). After a double-step liquid-liquid extraction, compounds are separated on a Symmetry C8 column eluted with a gradient of acetonitrile-phosphate buffer 10 mM pH 3.8 and detected at 230 nm and 290 nm. Calibration curves were linear in the range 25 to 500 ng/mL (100-2000 ng/mL for venlafaxine and its metabolite). The limit of quantification was 25 ng/mL (100 ng/mL for venlafaxine and its metabolite). For all quality controls good accuracy was achieved (93% to 99.5%) with intraday and interday variation coefficients less than 12%. This method allows simple and rapid (run time 18 min) identification and quantification of the eight new antidepressants and five of their active metabolites. This method can be used for toxicologic purpose.

[Pharmacologic basis for using paracetamol: pharmacokinetic and pharmacodynamic issues]. / Bases pharmacologiques de l'emploi du paracétamol: aspects pharmacocinétiques et pharmacodynamiques.

The advantage of paracetamol (acetaminophen) is that it can be administered via the oral, intravenous or rectal routes. The last mentioned differs from the oral route in the slow and irregular absorption of the active substance. At therapeutic concentrations, the pharmacokinetics of paracetamol are linear--that is, independent of the dose, and constant with repeated administration. The efficacy of paracetamol has been demonstrated in a wide variety of acute or chronic painful syndromes. In adults, the optimum unit dose is 1 g. The maximum daily dosage is 4 g, consistent with the decline in analgesic activity, which is usually over 6 hours. With effervescent tablets, drug absorption and onset of action are more rapid than with conventional tablets. However, there is no direct correlation between serum concentrations of paracetamol and its analgesic or antipyretic effect. Paracetamol is the non-opiate analgesic of choice in elderly persons or patients with chronic renal insufficiency, and it is usually not necessary to reduce the dosage in such individuals, even though clearance is reduced. Although the bioavailability of paracetamol is not impaired in patients with chronic, benign liver diseases, the agent is contraindicated in those with hepatic insufficiency. It can be used during pregnancy and lactation. The very low level of paracetamol binding to plasma proteins, together with its hepatic metabolism, mainly through glucuronide or sulphate conjugation, account for the low risk of drug interactions with paracetamol, particularly with antivitamin K. When added to a traditional non-steroidal anti-inflammatory drug, paracetamol enhances the analgesic effect or allows the use of lower doses. It is more difficult to define the ideal dosage of paracetamol in children, because of the influence of age on its pharmacokinetics, and the relatively erratic bioavailability of suppositories. An oral dose of 15 mg/kg every 4 hours, up to a total of 60 mg/kg/day, is usually sufficient to achieve the desired analgesic or antipyretic effect.

Pharmacokinetic interaction between high-dose methotrexate and oxacillin.

An 18-year-old man received two high-dose methotrexate cycles for the treatment of an osteosarcoma. Fifteen grams of methotrexate were infused over 6 hours. During the second cycle, co-administration of oxacillin (1g/8h) resulted in prolonged and marked elevation of methotrexate plasma concentrations. The patient experienced acute toxicity with renal failure, myelosuppression, mucitis, fever, and dermatologic abnormalities. After an initial improvement with folinic acid rescue and hemodialysis, the patient died. Oxacillin may thus inhibit the elimination of methotrexate.

High-performance liquid chromatographic method for the simultaneous determination of the six HIV-protease inhibitors and two non-nucleoside reverse transcriptase inhibitors in human plasma.

A selective and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of the six human immunodeficiency virus (HIV)-protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) and the non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine) in a single run. After a liquid-liquid extraction with diethyl ether, the six protease inhibitors and the two non-nucleoside reverse transcriptase inhibitors are separated on a Stability RP18 column eluted with a gradient of acetonitrile and phosphate buffer 50 mmol/L pH 5.65. A sequential ultraviolet detection (5-minute sequence set at 240 nm for nevirapine acquisition, 22-minute sequence set at 215 nm for other antiretroviral drugs acquisition followed by a sequence set at 260 nm for internal standard acquisition) allowed for simultaneous quantitation of the six protease inhibitors, nevirapine, and efavirenz. Calibration curves were linear in the range 100 ng/mL to 10,000 ng/mL. The limit of quantitation was 50 ng/mL for all drugs except nevirapine (100 ng/mL). Average accuracy at four concentrations ranged from 88.2% to 110.9%. Both interday and intraday coefficients of variation were less than 11% for all drugs. The extraction recoveries were greater than 62%. This method is simple and shows a good specificity with respect to commonly co-prescribed drugs. This method allows accurate therapeutic monitoring of amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, efavirenz, and nevirapine.

Intraosseous lidocaine provides effective analgesia for percutaneous vertebroplasty of osteoporotic fractures.

PURPOSE: To assess the safety and efficacy of intraosseous lidocaine (IL), in comparison with iv nalbuphine and propacetamol (NP) for analgesia during percutaneous vertebroplasty (PV) in order to avoid general anesthesia in elderly patients. METHODS: Patients (age 68 +/- 13 yr, weight 66 +/- 6 kg) undergoing PV for osteoporotic fractures were randomized prospectively into two groups: NP (n=50) and IL (n=50). All patients were premedicated (oral hydroxyzine 1 mg.kg(-1)) and had skin infiltration with 5 mL of 1% lidocaine prior to vertebral puncture. Thirty minutes before the procedure, Group NP received, in a blinded manner, 50 mL of iv nalbuphine (0.3 mg.kg(-1)) and propacetamol (30 mg.kg(-1)) while Group IL received 50 mL of iv saline. During vertebral puncture, Groups NP and IL received, in a blinded manner, 1 mL.10 kg(-1) of intraosseous saline and 1% lidocaine respectively. Pain was assessed during vertebral puncture and cement injection with a four-point verbal rating scale. Additionally, lidocaine plasma kinetics were obtained in 11 IL patients. RESULTS: Analgesic efficacy was similar in the IL and NP groups (85 vs 84%). Group NP had more side effects. Lidocaine peak recorded concentration was 2.6 +/- 0.1 microg.mL(-1) i.e., about three times less than the reported toxic limits. CONCLUSION: IL is as effective as the association of iv NP for analgesia in PV. However, considering that both protocols were insufficient in about 15% of cases, other modalities are needed to further improve analgesia and avoid general anesthesia during vertebroplasty.

Derivatization of (+/-)-5-[(2-methylphenoxy)methyl]-2-amino-2-oxazoline, an imidazoline binding sites ligand, with (+)-(R)-alpha-methylbenzyl isocyanate for drug monitoring purposes.

The derivatization of racemic 5-[(2-methylphenoxy)methyl]-2-amino-2-oxazoline, developed as an imidazoline binding sites ligand, with (+)-(R)-alpha-methylbenzyl isocyanate was performed in chloroform. The reaction led to two pairs of diastereomers, which were separated by RP-HPLC. A kinetic study of the derivatization reaction was achieved in order to establish conditions suitable for experimental drug monitoring.