Surface anaesthetic

The use of local anaesthetics outside specialized surgical or anaesthetical practice is usually limited to infiltration anaesthesia, different surface anaesthetic methods, and (nerve) block of fingers and toes. Lo-... 

It is a surface anaesthetic used in eye for producing corneal anaesthesia for tonometry and does not cause mydriasis or any corneal damage. 

Disposition in the Body. Cocaine is normally only used as a surface anaesthetic in the eye, ear, nose, and throat because of the possibility of systemic toxic effects when given by other routes. Addicts may inject it or use it as a snuff it is less toxic when taken orally due to hydrolysis in the gastro-intestinal tract. 

Absorption from mucous membranes on topical application varies according to the compound. Those that are well absorbed are used as surface anaesthetics (cocaine, lidocaine, prilocaine). Absorption of topically applied local anaesthetic can be extremely rapid and give plasma concentrations comparable to those obtained by injection. This has led to deaths from overdosage, especially via the urethra. 

Cocaine (alkaloid) is used medicinally solely as a surface anaesthetic (for abuse toxicity, see p. 192) usually as a 4% solution, because adverse effects are both common and dangerous when it is injected. Even as a surface anaesthetic sufficient absorption may take place to cause serious adverse effects and cases continue to be reported only specialists should use it and the dose must be checked and restricted. Cocaine prevents the uptake of catecholamines [adrenaline (epinephrine), noradrenaline (norepinephrine)] into S5nnpathetic nerve endings, thus increasing their concentration at receptor sites, so that cocaine has a built-in vasoconstrictor action, which is why it retains a (declining) place as a... 

It is a surface anaesthetic having effects similar to those of cocaine, but it exhibits more rapid onset of action followed by a prolonged action. 

It is a potent surface anaesthetic mainly used in ophthalmology and induces no initial irritation. Beeause of its rapid onset of aetion it is useful for most occular procedures that require topical anaesthesia such as tonometry, removal of foreign particles, gonioscopy and various short operative procedures which may involve the conjunctiva and cornea. It has also been reported to be employed frequently as a surface anaesthesia in glaucoma surgery and in cataract operations. 

It is a surface anaesthetic and has been used as a lotion or ointment in a eoneentration of 0.5% for the relief of irritation, itehing, burning or pain in dermatoses, ineluding mild sunburn and nonspeeifie pruritus. It is reported to be less toxic than dibucaine but more toxie than proeaine. 

It is a surface anaesthetic which possesses very low degree of toxicity and sensitization. It may be applied locally in a 1% strength to soothen pain in hemorrhoids and rectal surgery, itching dermatoses, some intubation procedures, anogenital pruritus and moderate bums and sunburn. 

Non-opioid analgesics with predominantly peripheral action, mostly inhibiting prostaglandin synthesis (conductive and surface anaesthetics). 

White crystals, m.p. 90-9 rC. Prepared fromp-nitrotoluene by way of p-aminobenzoic acid. It is used as a local anaesthetic on mucous surfaces internally and by injection, and is taken internally to relieve gastric pain. 

Sedated and anaesthetized rats received a lateral (mini-) thoracotomy and a pistil (3x6mm chilled to -193° G) was advanced through the hole in the chest and pressed onto the surface of the heart for 30 sec. The procedure was repeated 10 times in order to generate a cryolesion of reproducible size. GFP-transduced mesenchymal stem cells were directly injected into the borderzone of the developing ischemia (2x left lateral, 2x right lateral, lx apical). Each injection contained 8x10 mesenchymal stem cells in a volume of 30 pi (Jaquet et al., 2005). 

III.b.8.1. Skin. Surface anaesthesia of the skin can be produced with help of a cream containing a eutectic mixture of local anaesthetics (EMLA), which is a water/oil emulsion of equal parts of prilocaine and lidocaine with particularly good penetration capacity. EMLA is applied under occlusion, around 40-60 minutes before the planned intervention. This is an effective way of producing anaesthesia before needle punctures and minor, painful, procedures. The method is excellent, particularly in paediatrics, to reduce fear and pain. 

Raising the concentration of Ca in the medium pathing, a nerve may relieve conduction block produced by local anesthetics. Relief occurs because Ca alters the surface potential on the membrane, and hence the transmembrane electrical field. This, in turn, reduces the degree of inactivation of the Na channels and the affinity of the latter for the local anaesthetic molecule [25, 27]. 

It is another local anaesthetic with longer action but most toxic. It is used for surface anaesthesia. 

The alveolar-capillary membrane is normally very thin, has a huge surface area, and a large blood supply. Drugs given by this route, such as bronchodilators and pulmonary steroids, are rapidly absorbed into the bloodstream. This is also the route for administering the inhalational anaesthetics. DRUG METABOLISM AND EXCRETION... 

EMLA cream (lidocaine (lignocaine) 2.5% and prilocaine 2.5%) is an emulsion in which the oil phase is a eutectic mixture of lidocaine and prilocaine in a ratio of 1 1 by weight. It is available in 5 g and 30 g tubes. It is also available as an anaesthetic disc. This consists of a single-dose unit of EMLA contained within an occlusive dressing. The disc contains 1 g EMLA emulsion, the active contact surface being approximately 10 cm2. The surface area of the entire anaesthetic disc is approximately 40 cm2. EMLA (1 g) contains lidocaine 25 mg, prilocaine 25 mg with thickening agents, water, NaHCOB, etc., at a pH of about 9. 

A surface structure of a malignant cell consisting of regions will tend to fuse with any other plasma membrane. This tendency will be strongly enhanced if the other cell also has the same kind of surface structure. The presence of a general anaesthetic agent will induce a phase trcmsition from the planar bilayer (La) towards an intrinsically curved bilayer as in tihe cubic phase. The induction of metastasis by anaesthetic is then an obvious and expected phenomenon, imavoidable, and independent of the anaesdietic used. 

The topical anesthetics in general use in the horse are 0.5% proxymetacaine (proparacaine) and 0.5% tetracaine (amethocaine). The rate of onset and duration of clinical anesthesia of the ocular surfaces using these agents in the horse is not known. However, in general, repeated instillations at 30-60 s intervals over a 5 min period will superficially desensitize the normal eye for around 15 min. In the presence of conjunctival hyperemia, there is likely to be accelerated loss of the drug into the systemic circulation and instillation of the anaesthetic agent at shorter intervals for a longer period may be necessary to desensitize the ocular surfaces effectively. 

Although many refrigerants, propellants and anaesthetics are non-toxic, in the presence of a flame or on contact with very hot surfaces, phosgene may be produced as one of the toxic decomposition products. The chlorofluorocarbons, CCI3F (CFC-11), CQjF (CFC-12) and CjCljF, (CFC-114), when exposed to a gas flame, all generate phosgene as one of the... 

The patient probably has a chalazion (meibomian cyst), which can develop following a stye. It may enlarge and grow inwards and start to rub against the eye surface. Removal is usually a simple process under local anaesthetic. There is no treatment you can suggest but you can advise him to see his doctor to arrange to have it removed. 

The mechanism of inhibition in near-atmospheric CO2 is related to both metabolism and the function of the plasma membrane (24). The permeability of the cellular membrane to dissolved, unhydrated CO2, a neutral molecule, creates disorder and alters the membrane fluidity even at near-atmospheric pressures. However, unlike typical small anaesthetic molecules which alter membrane fluidity, the water permeability of the cell decreases upon contact with CO2 (24). Jones and Greenfield (24) suggest that this unique property of CO2 inhibition is due to the presence of the bicarbonate ion, which may act on the phospholipid head groups and the proteins near the surface of the membrane to alter the surface charge of the cell. 

The induction of unconsciousness may be the result of exposure to excessive concentrations of toxic solvents such as carbon tetrachloride or vinyl chloride, as occasionally occurs in industrial situations (solvent narcosis). Also, volatile and non-volatile anaesthetic drugs such as halothane and thiopental, respectively, cause the same physiological effect. The mechanism(s) underlying anaesthesia are not fully understood, although various theories have been proposed. Many of these have centred on the correlation between certain physicochemical properties and anaesthetic potency. Thus the oil water partition coefficient, the ability to reduce surface tension and the ability to induce the formation of... 

The presence of hydrophilic and hydrophobic regions in the same molecule is not a monopoly of surfactants most drug molecules feature hydrophilic and hydrophobic regions as well, and this is indeed the structural requirement for their ability to permeate cell membranes and pass absorption barriers. The amphiphihc properties are obvious in some drug classes, e.g. the local anaesthetics. On some occasions a drug substance may exceed the CMC, whereupon micellar self-solubilization can occur. A recent example was described by Hussain and coworkers who found that the hydrochloride of the basic analgesic DuP 747 is surface active the saturated solution (3 mg ml - at 22°C) lowered the surface tension of water to 50dyncm. It was hoped... 

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