Determination of tetracaine hydrochloride by fluorescence quenching method with some aromatic amino acids as probes.

A novel fluorescence quenching method for the determination of tetracaine hydrochloride (TA·HCl) concentration with some aromatic amino acids as fluorescence probe has been developed. In pH 6.3 acidic medium, tryptophane (Trp), tyrosine (Tyr) or phenylalanine (Phe) can react with tetracaine hydrochloride to form an ion-association complex by electrostatic attraction, aromatic stacking interaction and Van der Waals' force, which lead to fluorescence quenching of above amino acids. The maximum fluorescence excitation and emission wavelengths of them are located at 278, 274, 258 nm and 354, 306, 285 nm, respectively. The relative fluorescence intensity (F (0)/F) is proportional to the TA·HCl concentration in certain range. The linear ranges and detection limits are 1.2-5.0 µg/mL and 0.37 µg/mL for Tyr-TA·HCl system, 1.3-6.0 µg/mL and 0.38 µg/mL for Trp-TA·HCl system, and 1.4-6.0 µg/mL and 0.41 µg/mL for Phe-TA·HCl system. The optimum reaction conditions, influencing factors and the effect of coexisting substances are investigated. And the results show the method has a good selectivity. Judging from the effect of temperature, the Stern-Volmer plots and fluorescence lifetime determination, the quenching of fluorescence of amino acids by TA·HCl is a static quenching process.

Oxidative imbalance in patients with mild cognitive impairment and Alzheimer's disease.

Increasing evidence supports a role of oxidative imbalance, characterized by impaired antioxidant enzymatic activity and increased reactive oxygen species (ROS) production, in mild cognitive impairment (MCI) and Alzheimer's disease (AD) pathogenesis. Hyperhomocysteinemia, another risk factor for AD, also contributes to oxidative damage. Plasma total homocysteine (tHcy) and ROS levels, and total antioxidant capacity (TAC) were determined in 71 AD, 36 MCI and 28 vascular dementia (VaD) patients as well as in 44 age-matched controls. tHcy levels were significantly increased in patients with AD and VaD an a trend towards an increase in multiple domain MCI was observed. TAC was significantly decreased in AD as well as MCI, but not in VaD patients. In AD patients, a negative correlation was found between TAC and disease duration. ROS levels did not differ among groups, but were correlated with age. In conclusion, a pattern characterized by increased tHcy levels and decreased TAC is present in AD as well as MCI patients. While increased tHcy levels were also found in VaD, TAC modifications occur specifically in AD. ROS levels appear to be correlated with age rather than with a specific dementing disorder, thus leading to the hypothesis that oxidative imbalance observed in AD could be due to a decreased TAC.

Simultaneous determination of mepivacaine, tetracaine, and p-butylaminobenzoic acid by high-performance liquid chromatography.

INTRODUCTION: The purpose of the present study was to develop a simple method for the simultaneous determination of mepivacaine, tetracaine, and p-butylaminobenzoic acid (BABA) in human plasma using high-performance liquid chromatography (HPLC) with a multiwavelength detector. METHODS: Human blood samples containing heparin, as an anticoagulant, and physostigmine (100 microg/ml), as an anticholinesterase, or human plasma containing physostigmine were spiked with various concentrations of mepivacaine, tetracaine and, in some cases, BABA. Blood samples were centrifuged and plasma was deproteinized with trifluoroacetic acid (TFA; 7%). After centrifugation, the pH was adjusted to 4.5 and an aliquot of 20, 50 or 100 microl was injected into the HPLC apparatus. The detection was done simultaneously at wavelengths of 214 and 300 nm. Analytical chromatography was done on a Waters microBondapak C(18) reverse-phase column (3.9 x 300 mm; particle size 10 microm) with a 30-min increasing linear gradient of 20-40% acetonitrile+0.05% TFA in H(2)O+0.05% TFA at a flow rate of 1 ml/min. The Waters HPLC system included two pumps, an automatic injector, a column oven, and a M490 multiwavelength detector. Quantification was done using integration of peak areas with peaks of authentic mepivacaine, tetracaine, and BABA standards. RESULTS: Calibration curves for standards of mepivacaine, tetracaine, and BABA were linear in the concentration ranges from 0.1 to 100 microg/ml, and the correlation coefficients exceeded.99 for all compounds. The lower limits of detection were 100 ng/ml for mepivacaine and 50 ng/ml for tetracaine and BABA. The yields for mepivacaine, tetracaine, and BABA were 91+/-2.1%, 82+/-3.3%, and 88+/-2.0% (mean+/-S.E.M., n=6), respectively. Degradation of tetracaine by human plasma at 37 degrees C was inhibited by physostigmine. DISCUSSION: The method is sensitive enough to allow blood concentration determinations of mepivacaine and tetracaine or its metabolite, BABA, following local anesthesia induced by these two drugs, especially when their toxic effect may be present. This method also may be useful in forensic medicine for determination of the cause of death after local anesthesia with mepivacaine and/or tetracaine.

Tetracaine versus lidocaine-prilocaine for preventing venipuncture-induced pain in children.

The efficacy of tetracaine cream versus that of lidocaine-prilocaine cream for the prevention of pain in children undergoing venipuncture was studied. Hospital inpatients 1-15 years of age received, on the back of each hand, a 30-minute application of tetracaine 4% cream or a 60-minute application of lidocaine-prilocaine cream (EMLA, Astra) before undergoing scheduled venipuncture. The phlebotomists in this open, randomized trial evaluated the efficacy of the cream at the moment of venipuncture as adequate, inadequate, or inconclusive. Blood samples were taken immediately after venipuncture from 10 patients one to five years of age to measure the serum concentrations of tetracaine and its metabolite, N-butyl-p-aminobenzoic acid. Lidocaine-prilocaine cream was significantly more efficacious in preventing pain than tetracaine 4% cream (97% of the former group [n = 32] had adequate pain relief, compared with 76% of the latter [n = 34]. The only adverse effects observed were mild local erythema in the tetracaine group and local skin blanching in the lidocaine-prilocaine group. No tetracaine could be detected in serum, and the serum concentrations of N-butyl-p-aminobenzoic acid ranged from 0 to 1.8 mg/l. Statistically, lidocaine-prilocaine cream was more efficacious than tetracaine 4% cream, but the difference is of minor clinical significance and is outweighed by the practical advantages of tetracaine 4% cream, namely the shorter application time, vasodilation and lower cost.

Blood concentrations of tetracaine and its metabolite following spinal anesthesia.

Blood concentrations of tetracaine and its metabolite, p-butylaminobenzoic acid, were measured after spinal anesthesia with tetracaine which had been administered to patients under going orthopedic surgery. Tetracaine, an ester anesthetic, was given to 10 patients, the dose was 8-14mg, and blood samples were collected 1, 2 and 6h after the injection of tetracaine. We used gas chromatography/mass spectrometry for purposes of analysis. Tetracaine was not detected in any blood sample, but the metabolite was detected in each sample with the mean concentrations of 126.5, 97.9 and 43.3ng/ml at 1, 2 and 6h, respectively. This data will be useful in determination of the cause of death after spinal anesthesia with tetracaine.

High-performance liquid chromatographic analysis of cocaine in human plasma.

A simple isocratic HPLC procedure for the analysis of cocaine in plasma, with or without an internal standard, is described for the first time. Basified plasma was extracted in ether, re-extracted in acetic acid, which was subsequently basified prior to the final extraction in n-hexane. The hexane extract was evaporated to dryness, reconstituted in the mobile phase and then chromatographed. A reverse-phase micro-particulate C-18 column, a pre-column, and a UV detector set at 232 nm were used. A mobile phase containing 75% methanol and 25% 0.05 mol/L potassium phosphate buffer (pH 6.6) was used at a flow rate of 0.8 mL/min. Cocaine in the range of 20 to 500 ng/mL in plasma was determined on the basis of (a) peak height and (b) ratio of peak height to that of tetracaine internal standard. On either basis a linear regression on concentration was determined. The correlation coefficients (r) were 0.993 and 0.988 for (a) and (b) respectively. Twenty-two commonly used drugs were examined for interference. Eight drugs were considered candidates for potential interference with cocaine; lidocaine and droperidol were found to interfere in actual patients' samples. Only meperidine was found to interfere with the internal standard. Cocaine was determined in plasma from patients who received cocaine and other drugs.

Blood investigation in a fatality involving the veterinary drug T-61.

A case involving an acute fatality resulting from self-administration of about 30 mL of T-61, a euthanasia solution, consisting of a mixture of embutramide, mebezonium, and tetracaine, in a 58-year-old veterinarian is presented. Forensic investigations consisted of an external body examination, during which 5 mL of fluorinated femoral blood was collected. Embutramide and tetracaine were quantitated using gas chromatography coupled to mass spectrometry after extraction with chloroform/isopropanol/n-heptane (50:17:33, v/v) at pH 9.5 and separation on an HP5-MS capillary column. Mebezonium was quantitated using liquid chromatography coupled to mass spectrometry after ion-pair extraction (saturated KI solution) with methylene chloride at pH 5.4 and separation on a 5-mm Nucleosil C18 column. Blood concentrations were 43.0, 6.5, and 0.21 mg/L for embutramide, mebezonium, and tetracaine, respectively. No other drugs, including ethanol, were detected.

Determination of ester-type local anesthetic drugs (procaine, tetracaine, and T-caine) in human serum by wide-bore capillary gas chromatography with nitrogen-phosphorus detection.

A sensitive method for simultaneous determination of ester-type local anesthetic drugs (procaine, tetracaine, and T-caine) has been developed using wide-bore capillary gas chromatography with nitrogen-phosphorus detection (GC-NPD). The extraction procedure, the experimental conditions for heptafluorobutyryl (HFB) derivative formation, and the percentage of the ester-type local anesthetic drugs from the human serum are described. The HFB derivatives of ester-type local anesthetic drugs showed sensitivity of approximately 2-3 fold higher than that without derivatization. The detection limits of HFB derivatives of the ester-type local anesthetic drugs were approximately 60-70 pg on column. Recoveries from the human serum were 85-94%. This method could be used to determine concentrations as low as 24-28 ng/mliters of the ester-type local anesthetic drugs.

The cardiovascular effects and pharmacokinetics of intranasal tetracaine plus oxymetazoline: preliminary findings.

BACKGROUND: The authors evaluated the cardiovascular effects and pharmacokinetics of an intranasal 3 percent tetracaine/0.05 percent oxymetazoline spray developed to provide needle-free anesthesia of maxillary teeth. METHODS: The authors administered to 12 participants a proposed maximum recommended dose (MRD) (18 milligrams tetracaine/0.3 mg oxymetazoline) as three bilateral pairs of 0.1-milliliter nasal sprays. They administered two times this dose (36 mg tetracaine/0.6 mg oxymetazoline) as six bilateral pairs one to three weeks later. The authors recorded the patients' heart rate, blood pressure and oxygen saturation. They drew blood samples at baseline and 15 times during the two hours after drug administration. RESULTS: Physiological measures remained fairly stable throughout the two-hour period, with small but significant decreases (P < .05) in heart rate at 40 and 50 minutes for the two-times MRD (6.1 beats/minute) and MRD (7.5 beats/minute) administrations, respectively, and a significant increase in diastolic blood pressure (5.9 millimeters of mercury) for the two-times-MRD administration at 90 minutes. Mean oxygen saturation remained above 99 percent. Tetracaine plasma levels were undetectable in most participants, whereas concentrations of its major metabolite parabutylaminobenzoic acid from the two-times-MRD administration were approximately twice that from the MRD administration. Oxymetazoline concentrations from the two-times-MRD administration were approximately 50 percent greater than those from the MRD administration, with a half-life of 1.72 to 2.32 hours. CONCLUSIONS: Intranasal tetracaine/oxymetazoline mist generally was well tolerated in study participants. CLINICAL IMPLICATIONS: The safety profile and pharmacokinetics of this intranasal formulation indicate that it appears to be generally well tolerated in patients for achieving anesthesia of the maxilla. Additional safety and efficacy data are required, particularly in patients with cardiovascular disease and other comorbidities.

Simultaneous determination of procaine, lidocaine, ropivacaine, tetracaine and bupivacaine in human plasma by high-performance liquid chromatography.

A simple and sensitive high-performance liquid chromatography with ultraviolet detection (HPLC-UV) method has been developed and validated for simultaneous quantification of five local anesthetics in human plasma: procaine, lidocaine, ropivacaine, tetracaine and bupivacaine. In an ice-water bath, 500 microL plasma sample, containing 100 microg/mL neostigmine methylsulfate as anticholinesterase, was spiked with carbamazepine as internal standard and alkalized by sodium hydroxide. Liquid-liquid extraction with ethyl ether was used for plasma sample preparation. The chromatographic separation was achieved on a Kromosil ODS C18 column with a mobile phase consisting of 30 mM potassium dihydrogen phosphate buffer (0.16% triethylamine, pH adjusted to 4.9 with phosphoric acid) and acetonitrile (63/37, v/v). The detection was performed simultaneously at wavelengths of 210 and 290 nm. The chromatographic analysis time was 13 min per sample. The calibration curves of all five analytes were linear between 0.05 and 5.0 microg/mL (r(2) > or = 0.998). Precision ranged from 1.4% to 7.9% and accuracy was between 91.7% and 106.5%. The validated method is applicable for simultaneous determination of procaine, lidocaine, ropivacaine, tetracaine and bupivacaine for therapeutic drug monitoring and pharmacokinetic study.

Preliminary study to assay plasma amethocaine concentrations after topical application of a new local anaesthetic cream containing amethocaine.

Plasma concentrations of amethocaine were measured after topical application of amethocaine cream 2 g (5% w/w) to the dorsum of the right hand of 10 adult volunteers. The cream was applied for 240 min and plasma was assayed for amethocaine and its metabolite p-n-butylaminobenzoic acid at 0, 30, 60, 90, 120 and 240 min in all 10 volunteers, and at 360 min in seven volunteers, by high pressure liquid chromatography. No amethocaine was detected in the plasma of seven volunteers. Plasma concentrations of amethocaine up to 0.20 mg litre-1 were observed in three volunteers. No significant side effects were seen and pain scores on insertion of a 16-gauge cannula were 0 in all subjects. We conclude that the absence of clinical toxicity in the 10 healthy volunteers was a reflection of slow absorption and tissue hydrolysis of amethocaine after topical dermal application.

Absorption of liposome-encapsulated tetracaine versus nonliposome-encapsulated tetracaine from open wounds in rabbits.

The plasma tetracaine concentration versus time profiles for liposome-encapsulated tetracaine (LET) versus nonliposome-encapsulated tetracaine (NLET) were determined after topical application to open wounds in six rabbits (three in LET and three in NLET). H3-tetracaine preparations of LET or NLET were applied randomly to uniform dermal lacerations in anesthetized rabbits. Plasma tetracaine concentrations (ng/mL) of arterial blood samples obtained were measured at predetermined intervals (0.25, 0.5, 1.0, 2.0, and 24 hours) by isotope tracer assay. Results (mean +/- standard deviation) showed the peak plasma tetracaine concentration (Cmax) and the time to Cmax were 40.8 +/- 5.1 ng/mL and 40.1 +/- 7.3 minutes for LET, and 117.8 +/- 9.7 ng/mL and 49.1 +/- 50.2 minutes for NLET. Plasma tetracaine concentrations at all samples times were significantly lower for LET versus NLET. Liposome encapsulation of topically applied tetracaine significantly decreases both the peak and overall plasma tetracaine concentrations compared with the nonencapsulated form. The data suggest that liposome encapsulation of topically applied local anesthetics such as a solution of tetracaine, adrenaline, and cocaine, might reduce the potential systemic toxicity caused by rapid absorption of these compounds.

Intercostal nerve blockade for evaluation of local anaesthetic agents.

Bilateral intercostal nerve block provides the opportunity to subject as many as 16 separate peripheral nerves in a single subject to known or unknown local anaesthetic agents in a variety of concentrations, volumes, and additives. It permits the observation of local (e.g., neuritis), clinical (e.g., onset and duration), and systemic (e.g., toxicity and blood concentration) effects of these variables. In double-blind studies, bilateral intercostal nerve block allows the use of each side of the trunk for comparison of two experimental drugs, a new drug against a standard, or two new drugs. Subtle differences in clinical properties as well as simultaneous blood concentrations may be detected in these studies. The advantages of this technique in evaluating local anaesthetic agents are primarily the use of a single subject as his own control while studying may separate peripheral nerves. This aids appreciably in limiting the variable of age, temperature, and perfusion, as well as techniques of administration and evaluation. The constancy of the anatomy of the intercostal nerve provides a highly reliable and reproducible block technique.

Plasma cocaine and tetracaine levels following application of topical anesthesia in children.

STUDY OBJECTIVES: To measure plasma cocaine and tetracaine levels in children after standardized application of a solution of tetracaine 0.5%, epinephrine 0.05%, and cocaine 11.8% (TAC) to lacerations requiring suture repair. DESIGN: Nonrandomized, controlled trial over a five-month period. SETTING: University hospital emergency department. TYPE OF PARTICIPANTS: Stable children less than 16 years of age with uncomplicated lacerations. MEASUREMENTS AND MAIN RESULTS: Blood was obtained at either 15 or 20 minutes (early; 32) or 45 or 60 minutes (late; 45) for measurement of plasma cocaine and tetracaine levels. Analysis for cocaine and tetracaine concentrations was performed using gas chromatography-mass spectroscopy with a limit of detection for both assays of 0.5 ng/mL. Serum cocaine levels were low but measurable at both times in 75% of children. No tetracaine was measurable. Median cocaine levels were 1 ng/mL (range, 0 to 112 ng/mL) for the early group and 2 ng/mL (range, 0 to 274 ng/mL) for the late group (P = NS). Only two children had levels of more than 100 ng/mL. No significant correlation between patient or laceration characteristics and cocaine levels was detected. No significant change in heart rate or blood pressure was detected. Children who required additional local anesthesia had nonfacial lacerations and lower cocaine levels than children with facial lacerations. CONCLUSION: Application of 3 mL of standard TAC solution for 15 minutes results in low but measurable plasma cocaine levels in 75% of children.

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.

Plasma cocaine and tetracaine levels following application of topical anesthesia in a swine laceration model.

Standard TAC (0.5% tetracaine, 0.05% epinephrine, and 11.8% cocaine) solution is finding increased use as a topical anesthetic for lacerations. The extent of systemic absorption of TAC components and their resultant physiologic effects are unclear. Absorption of cocaine or tetracaine may result in serious toxicity. The investigators hypothesized that there are no measurable plasma cocaine or tetracaine levels after application of TAC in a swine laceration model. After an overnight fast 10 domestic swine underwent tracheostomy, mechanical ventilation, femoral venous, and arterial cannulation. Maintenance anesthesia with intermittent thiopental and pancuronium was provided to maintain stage III anesthesia. Heart rate (HR), arterial pressure (BP), plasma cocaine, and tetracaine levels were measured at intervals for 180 minutes. Five milliliters of TAC was applied for 15 minutes to a standardized facial laceration in experimental swine (n = 5). Randomly labeled plasma samples were placed in vials containing 2% sodium fluoride and 1% potassium oxalate, immediately refrigerated, and analyzed for cocaine and tetracaine using gas chromatography and mass spectroscopy. Significant changes in HR and mean BP, compared with baseline values, were analyzed using Dunnett's multiple range test. Plasma cocaine levels were measurable in all experimental swine after 10 minutes, while no tetracaine was detectable. No significant differences in HR or BP changes were observed between experimental and control subjects. Application of standard TAC solution results in measurable plasma cocaine levels, but not tetracaine. Further studies into anesthetic formulation, as well as timing and technique of application, are required before consensus on optimal emergency departmental use of topical anesthesia can be achieved.

Local anesthetics worsen renal function after ischemia-reperfusion injury in rats.

Local anesthetics are widely used during the perioperative period, even in patients with preexisting renal disease. However, local anesthetics have been shown to cause cell death in multiple cell lines, including human kidney proximal tubule cells. We questioned whether local anesthetics potentiate renal dysfunction after ischemia-reperfusion (I/R) injury in vivo. Rats were implanted with subcutaneous miniosmotic pumps that continuously delivered lidocaine (2 mg.kg-1.h-1), bupivacaine (0.4 mg.kg-1.h-1), tetracaine (1 mg.kg-1.h-1), or saline vehicle, and 6 h later the rats were subjected to 30 min of renal ischemia or to sham operation. Renal function was assessed by measurement of plasma creatinine at 24 and 48 h after renal I/R injury in the presence or absence of chronic infusions of local anesthetics and correlated to histological changes indicative of necrosis. The degree of renal apoptosis was assessed by three methods: 1) DNA fragmentation detected by terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling staining, 2) DNA laddering detected after agarose gel electrophoresis, and 3) morphological identification of apoptotic tubules at the corticomedullary junction. We also measured the expression of the proinflammatory markers ICAM-1 and TNF-alpha. Continuous local anesthetic infusion with renal I/R injury resulted in an increased magnitude and duration of renal dysfunction compared with the saline-infused I/R group. Additionally, both apoptotic and necrotic renal cell death as well as inflammatory changes were significantly potentiated in local anesthetic-treated rat kidneys. Local anesthetic infusion alone without I/R injury had no effect on renal function. We conclude that local anesthetics potentiated renal injury after I/R by increasing necrosis, apoptosis, and inflammation.

Increased haemodilution in hypotension induced by epidural anaesthesia.

This study examined whether the increased haemodilution from fluid loading in patients who develop hypotension at the onset of epidural anaesthesia (EDA) can be explained by high-level blockade or by stress-induced elevation of the blood glucose concentration. In 20 men aged between 53 and 87, crystalloid volume loading was carried out with 10 ml.kg-1 b.w. and EDA was induced with mepivacaine 2% and adrenaline 1:200,000. Irrespective of the blood pressure reaction to the blockade, there was no change in blood glucose level. A strong linear correlation between haemodilution and arterial pressure was found, in spite of unchanged blood glucose levels, in 10 patients in whom EDA was induced with bupivacaine 0.5%, and in 10 patients who received spinal anaesthesia with tetracaine 1%. There was no correlation between the haemodilution and the extent of sensory analgesia. These results support the view that low arterial pressure alone triggers the increased haemodilution observed during EDA-induced hypotension.