Formulation of local anaesthetics in different dosage forms, including those for oral, parenteral, and topical application have being widely investigated. All of these formulations include local anaesthetics in their salt forms. The lipophilic nature of the bases of local anaesthetics may influence the rate of the pharmacological effect. There has been very little research done towards this aspect of local anaesthetics. Prilocaine base and lignocaine base possess greater lipophilicity than their salts. The salt forms undergo dissociation in the body. To maximise the absorption rate lipophilicity plays an important role. The aim of the present study is to evaluate the potential of using prilocaine and lignocaine individually and in combination as bases for parenteral formulations using cyclodextrins as complexing agents. Cyclodextrins are widely used as complexing agents to increase the solubility of poorly soluble drugs. Hydroxypropyl-β-cyclodextrin (HPβCD) was the first choice amongst the different cyclodextrins to be evaluated as a solubility enhancer as it does not show nephrotoxicity and is more bio-available compared to other cyclodextrins. / Method: Prilocaine base was prepared from its salt and lignocaine base was obtained from Sigma Pharmaceuticals. Solubilities were examined individually and in combination by the phase solubility method and complex formation investigated. The mobile phase used was methanol:water (55:45) with phosphate buffer at pH 5.5. An AL type solubility isotherm was obtained for the influence of HPβCD on the solubilities of prilocaine and lignocaine. Complexation was investigated for both prilocaine and lignocaine to HPβCD by NMR. Results: The measured solubilities of prilocaine and lignocaine individually at 30% HPβCD from 25°C to 42°C were 1.96-7.91 moles/L and 1.69-4.55 moles/L respectively. The solubilities in combination were 0.91-3.68 moles/L for prilocaine and 1.03-8.35 moles/L for lignocaine respectively. The NMR data suggested that complexation involves the aromatic ring for both prilocaine and lignocaine apart from methene and methyl groups for prilocaine and ethyl amide and aromatic methyl groups for lignocaine.

Sample preparation as the first step in an analytical procedure has an important role, particularly in bioanalysis, because of the complexity of biological samples (blood plasma and urine). Biological matrix such as plasma and blood contains proteins, organic and inorganic salts, acids, bases and various organic compounds with similar chemistry to the analytes of interest. Thus the basic concept of a sample preparation method is to convert a real matrix into a format that is suitable for analysis by an analytical technique. Therefore the choice of an appropriate sample preparation method greatly influences the reliability and accuracy of the analysis results. The aim of this thesis was to develop and validate of microextraction by packed syringe (MEPS) as a fast, selective, accurate and fully automated sample preparation technique for determination of BAM peptides in human plasma and local anaesthtics in human plasma and urine samples using silica and polymer sorbents. First work presents use of MEPS technique online with LC-MS/MS as a tool for the quantification of BAM peptide in plasma samples. MEPS technique provides significant advantages such as the speed and the simplicity of the sample-preparation process. Compared with other extraction techniques, such as protein precipitation and ultrafiltration, MEPS gave cleaner samples and higher recovery. In the second work, MEPS technique was developed by using synthesized molecularly imprinted polymer (MIP) as a sorbent for selective quantification of a homologous series of local anaesthetics, containing lidocaine, ropivacaine, mepivacaine, and bupivacaine in human plasma and urine samples. Compared with other conventional sorbent, the use of MIP provides high selectivity of the extraction and decrease the matrix effect.

Background: Several studies have suggested that the likelihood of paraesthesia may depend on the local anaesthetic (LA) used. The purpose of this study was to analyze reports of paraesthesia among dental LAs used in the U.S. Methods: Reports of paraesthesia involving LAs between November 1997 through August 2008 were obtained from the U.S. Food and Drug Administration Adverse Event Reporting System. Chi-Square analysis compared expected frequencies, based on U.S. LA sales data, to observed reports of oral paraesthesia. Results: During the study period 248 cases of paraesthesia following dental procedures were reported. Most (94.5%) cases involved mandibular nerve block. The lingual nerve was affected in 89.0% of cases. Reports involving 4%-prilocaine and 4%-articaine were 7.3-times and 3.6-times, respectively, greater than expected (χ2, p<0.0001) based on LA usage by U.S. dentists. Conclusions: Consistent with previous reports, these data suggest that paraesthesia is more common following use of 4% LA formulations.

Background: Several studies have suggested that the likelihood of paraesthesia may depend on the local anaesthetic (LA) used. The purpose of this study was to analyze reports of paraesthesia among dental LAs used in the U.S. Methods: Reports of paraesthesia involving LAs between November 1997 through August 2008 were obtained from the U.S. Food and Drug Administration Adverse Event Reporting System. Chi-Square analysis compared expected frequencies, based on U.S. LA sales data, to observed reports of oral paraesthesia. Results: During the study period 248 cases of paraesthesia following dental procedures were reported. Most (94.5%) cases involved mandibular nerve block. The lingual nerve was affected in 89.0% of cases. Reports involving 4%-prilocaine and 4%-articaine were 7.3-times and 3.6-times, respectively, greater than expected (χ2, p<0.0001) based on LA usage by U.S. dentists. Conclusions: Consistent with previous reports, these data suggest that paraesthesia is more common following use of 4% LA formulations.

This thesis describes the host-guest chemistry between cucurbit[7]uril (CB[7]) and various series of guests, including neutral polar organic solvents, bis(pyridinium)alkane dications, local anaesthetics, acetylcholine analogues, as well as succinylcholine and decamethonium analogues, in aqueous solution. A focus of this thesis is the effects of varying the chemical structures within different series of guests upon the nature of the host-guest chemistry, such as the relative position and orientation of the guest relative to the CB[7] cavity, and the strengths of the binding affinities. The binding affinities of polar organic solvents with CB[7] depend upon the hydrophobic effect and dipole-quadrupole interactions. The polar guests align themselves so that their dipole moment is perpendicular to the quadrupole moment of CB[7]. The binding strengths of acetone and acetophenone to CB[7] decrease in the presence of alkali metals. Discrete 1:1 and 2:1 host-guest complexes are formed between CB[7] and a series of bis(pyridinium)alkane guests. In most cases the CB[7] initially occupies the aliphatic linker when the 1:1 complex is formed and migrates to the terminal regions as the second CB[7] is added. When bulky, hydrophobic tert-butyl substituents are present, however, the CB[7] occupies the terminal pyridinium region and not the central linker. Supramolecular complexes between CB[7] and a series of local anaesthetics have binding affinities 2-3 orders of magnitude greater than reported values with beta-cyclodextrin. The first pKa values of the guests increase by 0.5-1.9 units upon complexation. The binding positions of the guests within CB[7] differ in neutral and acidic media, with the systems thus behaving as pH-activated switches. With supramolecular complexes between CB[7] and various cationic cholines and their phosphonium analogues, the CB[7] cavity is occupied by the charge-diffuse cationic region. The binding affinities and positions vary depending on the nature of the onium group as well as the substituents within the guest molecule. Host-guest complexes between CB[7] and dicationic acetylcholinesterase inhibitors have very strong 1:1 binding affinities, with 2:1 binding being significantly weaker. These binding affinities are related to the nature of the cationic onium groups, and the length and hydrophobicity of the connecting linkers. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-01-28 12:27:37.833

Orientador: Angélica de Fátima de Assunção Braga / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-24T07:44:34Z (GMT). No. of bitstreams: 1 Carvalho_VanessaHenriques_D.pdf: 2552683 bytes, checksum: d3aa5b35758ce570c520c2ba8cc486fc (MD5) Previous issue date: 2013 / Resumo: Os anestésicos locais (AL) podem interagir com os bloqueadores neuromusculares (BNM) e modificar as suas propriedades farmacocinéticas e farmacodinâmicas, no entanto o mecanismo dessa interação é controverso. Este estudo experimental, realizado em preparações nervo frênico - hemidiafragma de rato e músculo biventer cervicis de pintainho, teve por objetivo avaliar o efeito de diferentes AL na transmissão neuromuscular e sua influência no bloqueio produzido pelo pancurônio. Foram avaliados os seguintes parâmetros: efeito na transmissão neuromuscular dos AL (ropivacaína, levobupivacaína, mistura em excesso enantiomérico de bupivacaína) e do pancurônio empregados isoladamente; o bloqueio produzido pelo pancurônio em preparações previamente expostas aos AL; a eficácia da neostigmina e da 4-aminopiridina na reversão do bloqueio neuromuscular produzido pelo pancurônio isoladamente e em preparações previamente expostas aos AL; a ação dos AL na resposta contraturante à acetilcolina; seus efeitos nos potenciais de membrana e nos potenciais de placa terminal em miniatura. Os resultados foram expressos em médias e desvios padrão e analisados através dos testes t de Student, Wilcoxon, Anova, Kruskall-Wallis e Mann-Whitney. Adotou-se um nível de significância de 5% (p<0,05). Na preparação nervo frênico - hemidiafragma de rato, os AL nas concentrações empregadas, não alteraram a amplitude das respostas musculares mas, potencializaram o efeito do pancurônio. O bloqueio neuromuscular foi parcial e totalmente revertido com a neostigmina e com a 4-aminopiridina, respectivamente. Não causaram alteração significativa nos potenciais de membrana e produziram diminuição progressiva na amplitude e na frequência dos potenciais de placa terminal em miniatura. Na preparação biventer cervicis de pintainho os AL, com exceção da ropivacaína, promoveram diminuição na resposta contraturante da acetilcolina. Os resultados obtidos neste estudo demonstram um sinergismo entre os fármacos estudados, resultante das ações pré e pós-juncionais dos anestésicos locais / Abstract: Local anaesthetics (LA) may interact with neuromuscular blockers and modify their pharmacokinetic and pharmacodynamic properties. However, the mechanism of this interaction is controversial. This experimental study, conducted in rat phrenic nerve diaphragm preparations and chick biventer cervicis, aimed to evaluate the effect of different LA in neuromuscular transmission and its influence on pancuronium induced blockade. The following parameters were evaluated: the effect on neuromuscular transmission of LA (ropivacaine , levobupivacaine mixture enantiomeric excess bupivacaine) and pancuronium used in isolation; the blockade produced by pancuronium in preparations previously exposed to LA; the effectiveness of neostigmine and 4 - aminopyridine in the reversal of neuromuscular blockade produced by pancuronium alone and in preparations previously exposed to AL; the action of LA in the contractile response to acetylcholine; its effects on membrane potentials and miniature endplate potentials. The results were expressed as means and standard deviations and analyzed using Student's t, Wilcoxon, ANOVA, Kruskal-Wallis and Mann-Whitney tests. A significance level of 5 % (p < 0,05) was adopted . In the rat phrenic nerve diaphragm preparation the LA, in the concentrations used, did not alter the amplitude of muscle response but potentiated the effect of pancuronium. Neuromuscular blockade was partially and fully reversed with neostigmine and 4- aminopyridine, respectively. There was no significant change in membrane potential and a progressive decrease in the amplitude and frequency of miniature endplate potentials was produced. In the chick biventer cervicis preparation the LA, with the exception of ropivacaine, led to a decrease in the contractile response to acetylcholine. The results of this study demonstrate a synergistic effect between the drugs studied, resulting from prejunctional and postjunctional actions of LAs / Doutorado / Farmacologia / Doutora em Farmacologia

Sample preparation is often a bottleneck in systems for chemical analysis. The aim of this work was to investigate and develop new techniques to address some of the shortcomings of current sample preparation methods. The goal has been to provide full automation, on-line coupling to detection systems, short sample preparation times and high-throughput. In this work a new technique for sample preparation that can be connected on-line to liquid chromatography (LC) and gas chromatography (GC) has been developed. Microextraction in packed syringe (MEPS) is a new solid-phase extraction (SPE) technique that is miniaturized and can be fully automated. In MEPS approximately 1 mg of sorbent material is inserted into a gas tight syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. Evaluation of the technique was done by the determination of local anaesthetics in human plasma samples using MEPS on-line with LC and tandem mass spectrometry (MS-MS). MEPS connected to an autosampler was fully automated and clean-up of the samples took about one minute. In addition, in the case of plasma samples the same plug of sorbent could be used for about 100 extractions before it was discarded. A further aim of this work was to increase sample preparation throughput. To do that disposable pipette tips were packed with a plug of porous polymer monoliths as sample adsorbent and were then used in connection with 96-well plates and LC-MS-MS. The evaluation of the methods was done by the analysis of local anaesthetics lidocaine and ropivacaine, and anti-cancer drug roscovitine in plasma samples. When roscovitine and lidocaine in human plasma and water samples were used as model substances, a 96-plate was handled in about two minutes. Further, disposable pipette tips may be produced at low cost and because they are used only once, carry-over is eliminated.