Lidocaine effects

Although an intermediate endpoint is associated with clinical benefit/ this benefit may be more than offset by the adverse effects of drug therapy when the ultimate outcome is considered. For example/ ventricular fibrillation is associated with increased mortality in the setting of acute myocardial infarction. The demonstration that lidocaine effectively prevents ventricular fibrillation in myocardial infarction patients at first provided a rationale for treating these patients prophylactically with this drug (7). However/ subsequent meta-analyses of several studies by MacMahon (8) and Hine (9) indicated that this use of lidocaine therapy actually worsens patient... 

Induction doses (Table 13-2) are accompanied by a high incidence of pain on injection and myoclonic movements. Lidocaine effectively reduces the pain of injection myoclonic movements can be reduced by premedication with either benzodiazepines or opiates. Long-term infusions are not recommended for reasons discussed below. 

Trialkylammonium salts, such as lidocaine hydrochloride, are titrated in an aqueous solution containing a surfactant. The presence of the surfactant increases the trialkylammonium salt s K , giving a titration curve with a more pronounced break. The effect of adding an immiscible organic solvent, such as methylene chloride or toluene, also is demonstrated. 

Ventricular fibrillation should be terminated by electrical defibrillation. Alternatively, lidocaine can be injected intravenously. In cases with lower frequency, ventricular tachyarrhythmia class I diugs such as aj marine, flecainide or propafenone are more effective as a result of the use-dependence of lidocaine. For prophylaxis treatment, amiodarone or sotalol may be helpful or the implantation of a cardioverter-defibrillator system. Acute amiodarone (i.v. in higher doses) can also terminate ventricular tachyarrhythmias. This action, however, seems to be mediated by its INa-blocking side effects and not (or less) by its class III like effects. 

Quaternary ammonium salts such as carcainium chloride (RSD 931) have been shown to be antitussive whilst having much reduced local anaesthetic activity. Whilst the molecular mechanisms underlying this antitussive activity is not understood, RSD 931 appears to be A8 fibre selective and may represent a novel class of antitussive drug. More recently JMF2-1 a lidocaine derivative that blocks Na+ channels has had beneficial effects in the airways without significant local anaesthetic activity. 

Anaesthetics such as lidocaine and tetracaine reversibly block the generation and conduction of action potentials in primary afferent fibres without inducing systemic effects when applied locally to dermatotomes. Their... 

Propranolol may increase procainamide plasma levels. Additive cholinergic effects may occur when procainamide is administered with other drugp with anticholinergic effects. There is the potential of additive cardiodepressant effects when procainamide is administered with lidocaine. When a beta blocker, such as Inderal, is administered with lidocaine, there is an increased risk of lidocaine toxicity. 

Local anesthetics interact with peripheral nerve cell membranes and exert a pharmacological effect [34]. Potential oscillation was measured in the presence of 20 mM hydrochlorides of procaine, lidocaine, tetracaine, and dibucaine (structures shown in Fig. 16) [19]. Amplitude and the oscillatory and induction periods changed, the extent depending on the... 

Lidocaine (less effective than above interventions)... 

The answer is e. (Hardman, pp 858-874.) Because verapamil, a Ca channel blocker, has a selective depressing action on AV nodal tissue, it is an ideal drug for both immediate and prophylactic therapy of supraventricular tachycardia (SVT). Nifedipine, another Ca channel blocker, has little effect on SAT Lidocaine and adenosine are parenteral drugs with short ha If-lives and, thus, are not suitable for prophylactic therapy. Procainamide is more suitable for ventricular arrhythmias and has the potential for serious adverse reactions with long-term use. 

The answer is d. (Hardman, pp 865-867.) Lidocaine usually shortens the duration of the action potential and, thus, allows more time for recovery during diastole. It also blocks both activated and inactivated Na channels. This has the effect of minimizing the action of lidocaine on normal myocardial tissues as contrasted with depolarized ischemic tissues. Thus, lidocaine is particularly suitable for arrhythmias arising during ischemic episodes such as myocardial infarction (Ml). 

Chemicals that are metabolized rapidly by the liver cannot be given for systemic effect by the enteral route because the portal circulation carries them directly to the liver. For example, lidocaine, a drug of value in controlling cardiac arrhythmias, is absorbed well from the gut, but is completely inactivated in a single passage through the liver. 

Schwartz, M.L., Meyer, M.B., Covino, B.G. and Narang, R.M. (1974). Antiarrhythmic effectiveness of intramuscular lidocaine Influence of different injection sites. J. Clin. Pharmacol. 14 77-83. 

Schmidt SH, Anniko M, Hellstrom S. 1990. Electrophysiological effects of the clinically used local anesthetics lidocaine, lidocaine-prilocaine and phenol on the rat s inner ear. Eur Arch Otorhinolaryngol 248 87-94. 

M. F. Powell, Stabibty of Lidocain in Aqueous Solution Effect of Temperature, pH, Buffer, and Metal Ions on Amide Hydrolysis , Pharm. Res. 1987, 4, 42-45. 

Similar to Voltaren" Emulgel, oily droplets of an eutectic mixture of lidocaine and prilocaine are dispersed in a hydrogel to provide local anesthesia to the skin for injections and siugical treatment (Emla cream). A further possibility is the dermal administration of a liposome dispersion as a spray (Heparin PUR ratiopharm Spriih-gel "). After administration, water and isopropylic alcohol evaporate partially resulting in an increase of concentration and in a transition from the initial liposome dispersion into a lamellar liquid crystal [32]. The therapeutic effect appears to be influenced favorably by the presence of lecithins rather than by the degree of liposome dispersion. 

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