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This article first looks at the pharmacokinetics of local anesthetic agents injected intravenously, and then looks at the possible practical applications of this technique: the choice of a local anesthetic agent as a function of its toxic side effects, the use of lidocaïne in local and regional intravenous anesthesia, and the treatment of cardiac rhythm disorders. Finally the article envisages the pharmacokinetics of local anesthetic agents used in local-regional anesthesia. This depends on the following factors: the site of injection, the dosage, the speed of injection, the possible addition of adrenalin and the nature of the local anesthetic itself. On the basis of a personal study the authors underline the difficulty of being precise in the pharmacokinetics of local anesthetic agents injected by the peridural route continuously or discontinuously.

The clinical usage of antiarrhythmic drugs may pose problems which could be solved by the direct application of the basic principles of pharmacokinetics. These problems involve the calculation of intravenous infusion rates and or oral dosages. Examples are provided by the rate of initial infusion of lignocaine in order to obtain a concentration within the therapeutic range, the eventual adjustment of this rate of infusion and the calculation of a loading dose. As regards the oral route, the calculation of the doses of procainamide is taken as an example. The estimation of the serum procainamide is a method for determining whether the dose should be increased or whether the drug is ineffective when no clinical result is observed. The pharmacokinetics of the main antiarrhythmic drugs are reviewed; procainamide, quinidine, propanolol, phenytoin, disopyramide. The therapeutic dose, clearance, extraction coefficient, bioavailability and half-life are the object of particular study. The fractioning of the dose and the total dose in a 24 hour period depend on these factors. The effects of cardiac, renal and hepatic failure on the clearance of each drug are recalled. These pharmacokinetic principles help the clinician not only in the prescription of an antiarrhythmic drug but also in deciding on the indications for drug serum concentration, estimations which are particularly useful in some difficult clinical situations, and in interpreting the results.

Intravenous regional anesthesia is a simple and effective method of analgesia of an extremity by intravenous injection of a local anesthetic while the circulation is interrupted. Although the pharmacokinetics of the injected drug is relatively well known, its precise mode of action is still not well understood. The complications of the technique are uncommon and generally minor ones. They occur immediately after tourniquet release. The relative and absolute contra-indications to the use of intravenous regional anesthesia are presented.

1. The aim of the present study was to investigate an eventual influence of the hour of administration on lidocaine kinetics in the rat. 280 Wistar AF SPF adult male rats were used for this study and maintained under controlled environmental conditions (LD: 06.00-18.00) during the month of October. A single 50 mg . kg-1 dose of lidocaine was given by intramuscular route, at four different fixed time points of a 24-hour period (i.e.: 10.00, 16.00, 22.00 and 04.00) to 70 rats. At each specified time point blood samples were taken 5, 15, 30 min., 1, 2, 4 and 6 hours after the drug administration. Lidocaine plasma levels (free and bound) were determinated according to a specific gas chromatographic method. 2. Our data showed circadian variations of pharmacokinetic parameters (Formula: see text) 3. Lidocaine free fraction varied with time and the protein binding of lidocaine showed a circadian variation. 4. The observed variations may be related to 1) daily fluctuations of absorption or binding of the drug 2) to diurnal variation of the hepatic drug metabolising enzymes responsible for the inactivation of the drug and/or 3) to diurnal variations in excretion rate of lidocaine. Finally our results agree with those of Lutsch and Morris who found a circadian periodicity in susceptibility to lidocaine in the mouse with maximal convulsant activity at 21.00.