Brucine-loaded liposomes composed of HSPC and DPPC at different ratios: in vitro and in vivo evaluation

OBJECTIVE

The objective of this study is to test the hypothesis that the phase transition temperature (T(m)), the main property of liposomes, can be easily controlled by changing the molar ratio of hydrogenated soy phosphatidylcholine (HSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphacholine (DPPC) after drug encapsulation.

MATERIALS AND METHODS

Brucine, an antitumor alkaloid, was encapsulated into the liposomes with different HSPC/DPPC compositions. The T(m)s of the brucine-loaded liposomes (BLs) were determined by differential scanning calorimetry (DSC). Then the physicochemical properties and pharmacokinetics of the BLs with different HSPC/DPPC compositions were investigated and compared.

RESULTS

The results of DSC revealed that HSPC and DPPC can combine into one phase. The findings of molecular modeling study suggested that HSPC interacts with DPPC via electrostatic interaction. The molar ratio of HSPC/DPPC influenced the sizes of BLs but had little effect on the entrapment efficiency (EE). The stability of BLs was improved with the increase of the HSPC ratios, especially with the presence of plasma. Following i.v. administration, it was found that AUC values of BLs in vivo were directly related to the HSPC/DPPC ratios of BLs, namely the T(m)s of BLs.

DISCUSSION

The behavior of liposomes, especially in vivo pharmacokinetic behavior, can be controlled by the modification of T(m).

CONCLUSION

The characterization of BLs in vitro and in vivo had demonstrated that the Tm could be flexibly modified for liposomes composed of both HSPC and DPPC. Using HSPC/DPPC composition may be an efficient strategy to control the T(m), thus control the in vivo pharmacokinetic behavior, of BLs.

[Optimization and application of method to determine plasma concentration of brucine]

The HPLC method for determining plasma concentration of brucine was optimized during the study on the effect of the extraction reagent, the extraction frequency and the volume of extraction solvent on the extraction recovery of brucine. The optimum sample treatment method was obtained in the study. Specifically, ammonia water was added, 4 mL extraction solvent (N-hexane-methylene chloride-isopropyl alcohol 65:30:5) were adopted to extract brucine for twice. The method to determine plasma concentration of brucine was applied in pharmacokinetic study to compare pharmacokinetic properties of intravenous injection (5 mg x kg(-1)) and transdermal administration (40 mg x kg(-1)) of brucine aqueous alkali. The results showed that both pharmacokinetic parameters of brucine after intravenous injection and transdermal administration were in conformity with the two-compartment model. After transdermal administration, the absolute bioavailability was calculated to be 18.72%. The optimized HPLC method can satisfy the demands of the pharmacokinetic study on brucine.

[Preparation and pharmacokinetics of brucine hydrogel patch]

OBJECTIVE

To investigate the effect of dose on pharmacokinetic properties of brucine hydrogel patch.

METHODS

The plasma concentration of brucine was determined by HPLC. Brucine hydrogel patch was prepared and its pharmaceutical characterization was investigated. After transdermal administration of different dose brucine hydrogel patch; Plasma concentration versus time profiles were determined and pharmacokinetic parameters were calculated by DAS program.

RESULTS

The pharmaceutical properties of brucine hydrogel patch were satisfactory. The AUC0-1 values were 7.24 +/- 0.61, 16.02 +/- 2.34 and 54.84 +/- 26.59 microg x h/mL after administration of 30, 60 and 180 mg/kg brucine hydrogel patch, respectively. The corresponding C(max) values were 0.73 +/- 0.23, 1.45 +/- 0.28 and 4.59 +/- 1.85 microg/mL, respectively. And the corresponding T(max) values were 8.67 +/- 2.07, 11.67 +/- 2.66 and 8.33 +/- 2.65 h, respectively.

CONCLUSION

The pharmacokinetic properties of brucine do not vary with the dose of brucine hydrogel patch.

[Quantitative determination of strychnine in blood and urine by gas chromatography with mass-selective detector]

A method for the quantitative determination of strychnine in biological fluids by gas chromatography--mass spectrometry is proposed. The preparation of samples for the analysis included extraction of strychnine from blood and urine with the use of AccuBond(II) EVIDEX cartridges for solid-phase extraction and SPEC MP3 disks respectively. The efficiency of extraction was estimated at 0.05 mg/l for blood and 0.02 mg/l for urine. The detection limit was 0.10 mg/l in blood and 0.05 mg/l in urine.

[Simultaneous screening for 22 poisonous alkaloids in blood by liquid chromatography-tandem mass spectrometry with multiple-reaction monitoring]

OBJECTIVE

To establish a liquid chromatography-tandem mass chromatography (LC-MS/MS) method for the simultaneous screening for 22 poisonous alkaloids in blood.

METHODS

This method involves a liquid-liquid extraction (LLE) followed by liquid chromatography-tandem mass spectrometry with multi-ple-reaction monitoring (MRM). After blood was extracted with buprenorphine as the internal standard, the target compounds were analyzed with LC-MS/MS-ESI in the positive ionization mode.

RESULTS

Identification was based on the compound's retention time and two precursor-to-product ion transitions. The limits of detection ranged from 0.1 ng/mL to 20 ng/mL in blood.

CONCLUSION

The method was sufficiently selective and sensitive to detect poisonous alkaloids and can be applied in forensic and clinical toxicology.

Application of high performance capillary electrophoresis on toxic alkaloids analysis

We employed CE to identify mixtures of the toxic alkaloids lappaconitine, bullatine A, atropine sulfate, atropine methobromide, scopolamine hydrobromide, anisodamine hydrobromide, brucine, strychnine, quinine sulfate, and chloroquine in human blood and urine, using procaine hydrochloride as an internal standard. The separation employed a fused-silica capillary of 75 microm id x 60 cm length (effective length: 50.2 cm) and a buffer containing 100 mM phosphate and 5% ACN (pH 4.0). The sample was injected in a pressure mode and the separation was performed at a voltage of 16 kV and a temperature of 25 degrees C. The compounds were detected by UV absorbance at wavelengths of 195 and 235 nm. All the ten alkaloids were separated within 16 min. The method was validated with regard to precision (RSD), accuracy, sensitivity, linear range, LOD, and LOQ. In blood and urine samples, the detection limits were 5-40 ng/mL and linear calibration curves were obtained over the range of 0.02-10 microg/mL. The precision of intra- and interday measurements was less than 15%. Electrophoretic peaks could be identified either by the relative migration time or by their UV spectrum.

Rapid separation of strychnine and brucine on a dynamically modified poly(dimethylsiloxane) microchip followed by electrochemical detection

A method has been developed for rapidly separating and detecting strychnine and brucine using a poly(dimethysiloxane) (PDMS) microchip and electrochemical (EC) detection. PDMS microchannels dynamically modified by Brij35 are shown to be more efficient than native ones. The two analytes are well separated within 90 s in 70 mmol/L acetate buffer (pH 5.5) containing 0.01% (v/v) Brij35. Detection limits were found to be 1.0 micromol/L for strychnine and 0.2 micromol/L for brucine at S/N = 3. The method was used to determine trace strychnine and brucine in rat serum, and the results obtained correlate well with those obtained via high-performance liquid chromatography (HPLC).

Determination of Strychnine in Human Blood using Solid-Phase Extraction and GC-EI-MS

A rapid, simple, and sensitive method has been developed for the identification and quantitation of strychnine in human blood. The sample cleanup procedure involved solid-phase extraction with Oasis(R) HLB cartridges. The extracts were analyzed by gas chromatography-electron impact ionization-mass spectrometry. Limits of detection (LOD) and quantitation (LOQ) were 0.03 and 0.10 microg/mL, respectively, and the method was found to be linear between the LOQ and 2.5 microg/mL, with a correlation coefficient of 0.9994. Intra- and interday precision and accuracy were determined at both low and high concentrations (0.50 and 2.00 microg/mL). The CVs ranged from 5.63 to 8.50% and bias was within +/- 10% of the true value. Mean recovery of strychnine was 90.7%. Because of its simplicity and speed, the described method can be applied in forensic toxicology laboratories to determine this alkaloid in whole blood samples. Also, the fact that only 0.5 mL of blood is required to accomplish the analysis make this procedure useful in situations where several exams are needed and the sample volume is limited.

Application of solid phase microextraction to the determination of strychnine in blood

A simple and rapid method based on solid phase microextraction (SPME) via direct immersion followed by gas chromatography coupled with electron impact ionization/mass spectrometry (GC/EI-MS) was developed for the determination of strychnine in blood. Papaverine was used as internal standard (I.S.). Two types of fibre coating were tested, 100 microm polydimethylsiloxane and 65 microm Carbowax/Divinylbenzene, the latter giving higher recoveries of the compound. The main factors affecting the SPME process, such as sample dilution (1:10), adsorption and desorption times (20 and 10 min, respectively), carry-over effect (not observed), pH and salt addition (no modifications on pH or salt concentration) were optimized. The procedure was validated in terms of linearity (r(2)=0.9992 for concentrations ranging from 0.10 to 5.00 microg/mL), intra and interday precision (0.93 and 4.62%, respectively at 0.50 microg/mL; 3.33 and 8.06%, respectively at 2.50 microg/mL), sensitivity (6.83 and 8.91 ng/mL for LOD and LOQ, respectively) and extraction recovery (0.54 and 0.39% at 0.50 and 2.50 microg/mL, respectively). The developed procedure was found suitable for forensic investigations and was considered a good alternative to the liquid-liquid extraction methods normally used for the determination of this compound in biological media.

[Concentration and determination of strychnine alkaloid in biological fluids]

OBJECTIVE

To establish a new method for determination of strychnine alkaloid in biological fluids based on molecularly imprinted polymers.

METHODS

A strychnine molecularly imprinted monolithic column was prepared by in-situ molecularly imprinted technique. The polymer was filled to a 1cm column, and a method was developed to concentrate and determine strychnine alkaloids in biological fluids.

RESULTS

the limit of detection of the method was 4.9 ng, and the recoveries were more than 92%. The relative standard deviations were smaller than 6.59%. The linear correlation coefficients of standard curves were 0.999 1 and 0.9966 respectively. This method was applied to concentrate and determine strychnine in plasma and urine of poisoned rabbit.

CONCLUSION

The new method could concentrate and simultaneously determine strychnine alkaloids in biological fluids, and it was applied to forensic toxicological analysis.

Liquid chromatography/photodiode array detection for determination of strychnine in blood: a fatal case report

An original liquid chromatography method with photodiode-array detection (DAD) is presented for the determination of strychnine in blood. This sensitive method allows the use of only 0.1 ml of sample. The strychnine was isolated from blood using a liquid-liquid extraction procedure and chloroquine as an internal standard. The limits of detection (LOD) and quantification were 0.06 and 0.5 mg/l, respectively. The recovery was 94% and the coefficients of variation (CV) ranged from 5.9 to 10.8%. A fatal case of strychnine poisoning is presented, with a lethal blood concentration of 25 mg/l.

Hypothalamic digoxin, hemispheric chemical dominance, and mesenteric artery occlusion

The role of the isoprenoid pathway in vascular thrombosis, especially mesenteric artery occlusion and its relation to hemispheric dominance, was assessed in this study. The following parameters were measured in patients with mesenteric artery occlusion and individuals with right hemispheric, left hemispheric, and bihemispheric dominance: (1) plasma HMG CoA reductase, digoxin, dolichol, ubiquinone, and magnesium levels; (2) tryptophan/tyrosine catabolic patterns; (3) free radical metabolism; (4) glycoconjugate metabolism; and (5) membrane composition. In patients with mesenteric artery occlusion there was elevated digoxin synthesis, increased dolichol and glycoconjugate levels, low ubiquinone, and elevated free radical levels. The RBC membrane Na(+)-K+ ATPase activity and serum magnesium were decreased. There was also an increase in tryptophan catabolites and reduction in tyrosine catabolites in the serum. There was an increase in cholesterol:phospholipid ratio and a reduction in glycoconjugate level of RBC membrane in these patients. The biochemical patterns obtained in mesenteric artery occlusion is similar to those obtained in left-handed/right hemispheric dominant individuals by the dichotic listening test. But all the patients with mesenteric artery occlusion were right-handed/left hemispheric dominant by the dichotic listening test. Hemispheric chemical dominance has no correlation with handedness or the dichotic listening test. Mesenteric artery occlusion occurs in right hemispheric chemically dominant individuals and is a reflection of altered brain function. Hemispheric chemical dominance may thus control the risk for developing vascular thrombosis in individuals.

Endogenous strychnine: description of hypo- and hyperstrychninergic state in relation to neuropsychiatric diseases

Previous work from our laboratory has demonstrated the presence of endogenous strychnine in the mammalian brain and human serum samples. The present study examines the role of strychnine in neuropsychiatric disorders. Strychnine is synthesized from tryptophan. The blood levels of tyrosine, tryptophan, and strychnine were studied as also RBC membrane Na(+)-K+ ATPase activity. It was found that serum tyrosine levels were reduced and that tryptophan levels were elevated in all neuropsychiatric disorders studied with a reduction in RBC Na(+)-K+ ATPase activity. Strychnine was present in significant amounts in the serum of patients with epilepsy, Parkinson's disease, and manic depressive psychosis. The presence of strychnine in significant amounts could be related to elevated tryptophan levels, suggesting the synthesis of these alkaloids from tryptophan. Na(+)-K+ ATPase inhibition present in most of the disorders could be related to increased depolarizing strychninergic transmission. The role of strychnine in the pathogenesis of these disorders, in the setting of membrane Na(+)-K+ ATPase inhibition, is discussed.

Case report: Survival after deliberate strychnine self-poisoning, with toxicokinetic data

INTRODUCTION

Strychnine poisoning is uncommon, and in most severe cases, the patient dies before reaching hospital. The management of strychnine poisoning is well documented, although there are few data on the kinetics of elimination of strychnine after overdose.

CASE REPORT

A 42-year-old man presented shortly after ingestion of an unknown quantity of strychnine powder. After a respiratory arrest, with intensive supportive management requiring admission to an intensive care unit, he survived. Eight serum samples were taken over the first 5 days and analysed subsequently for strychnine concentrations.

RESULTS

The initial concentration at 1.5 hours after ingestion was 4.73 mg/l, falling to 0.38 mg/l at 74 hours postingestion. Serum concentrations followed a monoexponential elimination curve with a calculated elimination half-life of 12 hours.

DISCUSSION AND CONCLUSION

Strychnine poisoning presents with classical features, and with early diagnosis and supportive management, the patient can survive. The initial serum concentration of 4.73 mg/l is the highest reported concentration in a patient who has survived. Previous reports of the elimination half-life have suggested it is between 10 and 16 hours, which conforms to the elimination data in our case.

Tryptophan and tyrosine catabolic pattern in neuropsychiatric disorders

Catabolism of tryptophan and tyrosine in relation to the isoprenoid pathway was studied in neurological and psychiatric disorders. The concentration of trytophan, quinolinic acid, kynurenic acid, serotonin and 5-hydroxyindoleacetic acid was found to be higher in the plasma of patients with all these disorders; while that of tyrosine, dopamine, epinephrine and norepinephrine was lower. There was increase in free fatty acids and decrease in albumin (factors modulating tryptophan transport) in the plasma of these patients. Concentration of digoxin, a modulator of amino acid transport, and the activity of HMG CoA reductase, which synthesizes digoxin, were higher in these patients; while RBC membrane Na+-K+ ATPase activity showed a decrease. Concentration of plasma ubiquinone (part of which is synthesised from tyrosine) and magnesium was also lower in these patients. No morphine could be detected in the plasma of these patients except in MS. On the other hand, strychnine and nicotine were detectable. These results indicate hypercatabolism of tryptophan and hypocatabolism of tyrosine in these disorders, which could be a consequence of the modulating effect of hypothalamic digoxin on amino acid transport.

Endogenous strychnine, nicotine, and morphine--description of hypo and hyper-strychninergic, nicotinergic and morphinergic state in relation to neuropsychiatric diseases

Previous work from this laboratory had demonstrated the presence of endogenous morphine, strychnine and nicotine in the mammalian brain and human serum samples. Morphine is synthesised from tyrosine and strychnine and nicotine from tryptophan. This study examines the role of strychnine, nicotine and morphine in neuropsychiatric disorders. The blood levels of tyrosine, tryptophan, strychnine, nicotine and morphine were studied as also RBC membrane Na(+)-K+ ATPase activity. It was found that serum tyrosine levels were reduced and tryptophan levels elevated in all neuropsychiatric disorders studied with a reduction in RBC Na(+)-K+ ATPase activity. Nicotine was present in significant amounts in serum of patients with schizophrenia, CNS glioma and syndrome X with multiple lacunar state. Morphine was present in significant amounts only in the serum of patients with multiple sclerosis and MDP. Strychnine was present in significant amounts in the serum of patients with epilepsy, Parkinson's disease and MDP. The presence of nicotine and strychnine in significant amounts could be related to elevated tryptophan levels suggesting the synthesis of these alkaloids from tryptophan. Morphine was not detected in most of the disorders owing to low tyrosine levels noted in them. Na(+)-K+ ATPase inhibition noticed in most of the disorders could be related to decreased hyperpolarising morphinergic transmission and increased depolarising nicotinergic and strychinergic transmission. The role of morphine, strychnine and nicotine in the pathogenesis of these disorders in the setting of membrane Na(+)-K+ ATPase inhibition is discussed.

Determination of atropine in biological fluids by micellar electrokinetic capillary chromatography in the presence of strychnine and tetracaine

The identification and quantitation of atropine, in whole blood and gastric contents in the presence of strychnine and tetracaine is described. This method uses liquid-liquid extraction and micellar electrokinetic chromatography (MECC). Separations are made using a 50 cm long capillary and a borate/phosphate buffer at pH 9.2 with 50 mM sodium dodecyl sulfate (SDS). Linearity was established for the three compounds between 1.0 and 100 microg/mL, using scopolamine as internal standard. The limit of detection for atropine was estimated at 0.06 microg/mL and the limit of quantitation at 0.2 microg/mL. The run time is less than 30 min. Alternate parameters are proposed to reduce the run time to under 10 min. The method was applied to a forensic post-mortem case.

Acute chemical pancreatitis associated with nonfatal strychnine poisoning

CASE REPORT

An 18-year-old female who accidentally ingested strychnine developed chemical pancreatitis in addition to the classical clinical picture of strychnine poisoning. Many drugs or chemicals have been reported to be associated with pancreatitis; however, this paper provides us with the first evidence that acute pancreatitis may follow strychnine poisoning. The patient survived despite the development of seizures, lactic acidosis, rhabdomyolysis, and pulmonary infiltrates. Toxicology testing confirmed the presence of strychnine in blood (2.17 mg/L), gastric aspirate, and urine. Attention is drawn to the fact that survival can follow the ingestion of large doses of strychnine providing there is no delay in diagnosis and treatment. The pathophysiologic mechanism of chemical pancreatitis is discussed.

Evaluation of an HPTLC method for the determination of strychnine and crimidine in biological samples

In an attempt to improve the sensitivity and selectivity of thin-layer chromatographic analysis for the detection of strychnine and crimidine in biological samples, a rapid high-performance thin-layer chromatographic (HPTLC) method with densitometry is described. Fortified dog serum and stomach content samples were analyzed after extraction with chloroform. Quantitation was achieved by densitometry in the ultraviolet (UV) range (260 nm) of HPTLC silica gel 60 plates. Detection of trace levels as low as 5 ng proved feasible. Linearity was obtained over a range of 10-250-ng deposits for crimidine and 12.5-250-ng deposits for strychnine with simple or F254 plates. No interferences were observed in the UV spectra (220-380 nm) when peaks obtained with HPTLC of the standard substances and positive biological contents were scanned.

Determination of strychnine and brucine by capillary zone electrophoresis

A procedure for quantitative estimation of strychnine and brucine in the extracts of Strychnos nux-vomica seeds by capillary zone electrophoresis (CZE) was developed. The buffer solution used was 10mM phosphate buffer-MeOH (9:1), pH 2.5. The linear calibration range was 0.01-0.15 mg/ml. This method is useful for the qualitative and quantitative determination of strychnine and brucine in plant drug samples, as well as in human plasma.

Enhanced elimination of theophylline, phenobarbital and strychnine from the bodies of rats and mice by squalane treatment

Our previous study suggested that squalane would be a good candidate for an antidote to reduce the toxicity of drug ingested accidentally at a high dose by enhancing the drug elimination from the body. In the present study, we investigated whether squalane given orally could enhance the elimination of theophylline, phenobarbital and strychnine which were administered parenterally to rats or mice. Squalane increased the fecal excretion of theophylline and reduced the serum level of the drug in rats. Squalane accelerated the fecal excretion of strychnine in mice. These results suggest that squalane may stimulate more the elimination of neutral (theophylline) or basic (strychnine) drugs which should be present in unionized form in intestinal lumen, than that of acidic drugs.

Massive strychnine intoxication: serial blood levels in a fatal case

A fatal case of strychnine intoxication is reported. The patient expired despite early aggressive management and prevention of metabolic complications. Serial blood levels are reported. In contrast to a previous report describing first order elimination kinetics, our data suggest that strychnine follows Michaelis-Menton elimination kinetics. The case illustrates the rapid, dramatic course of severe strychnine ingestions. A review of the toxicokinetics, mechanism of action and treatment of strychnine intoxication follows.

The influence of dosage form on papaverine bioavailability

The bioavailability of sustained-release papaverine HCl dosage forms were compared to equivalent doses of the drug administered as an elixir and conventional compressed tablets to 12 healthy human subjects. Papaverine plasma levels were determined using a gas-chromatographic procedure. The drug was absorbed more rapidly and completely from the two nonsustained-release formulations. There was a large intersubject variability, and the plasma half-life of the drug was esstimated to be 1 hour. The area under the plasma level-time curve for the nine sustained-release products ranged from 18 to 64% relative to the area achieved by the papaverine elixir. It was concluded that the sustained-release dosage forms of papaverine included in each study group could be considered bioequivalent, but they exhibited inadequate bioavailability relative to either the elixir or the compressed tablet dosage form.