Microdialysis technique

A number of recent publications indicate that the antibacterial field has adopted the concept of comparing free drug concentration at the site of action to in vitro drug potency reported as MIC [24-26]. A study of the antibacterial ertapenem in healthy volunteers was carried out to provide support for its use in skin and skin-structure infections [27]. Using microdialysis techniques, unbound drug concentrations in muscle and subcutaneous tissues were sampled at... 

Originating from the neurosciences, the microdialysis technique has been used since several years to monitor drug absorption and disposition or the levels of endogenous substances in the extracellular space of different organs and fluids, such as bone, lung, liver, brain, and blood. The method has evolved from its use in different animal species to the human microdialysis during the late 80s [35],... 

S. Macha and A. K. Mitra. Ocular pharmacokinetics in rabbits using a novel dual probe microdialysis technique. Exp. Eye Res. 72 289-299 (2001). 

Two in vivo microdialysis techniques are employed in the clinical setting open and closed, which refer to the degree of exposure of the brain (Kanthan and Shuaib, 1995). In the open technique, a craniotomy is performed to expose the brain and the microdialysis probe is then implanted into the brain region of interest. In the closed technique, a burr hole is made in the skull and a modified probe is then inserted into the brain via the burr hole. The closed technique permits multiple insertions of the dialysis probe into the brain tissue and consequently minimizes problems associated with prolonged probe placement, such as edema and gliosis (Kochs, 1997). Therefore, the closed technique allows for continuous but intermittent sampling and has lower risks of tissue damage and infection than the open method (Kanthan and Shuaib, 1995). 

Ricci F, Moscone D, Palleschi G. Ex vivo continuous glucose monitoring with microdialysis technique the example of GlucoDay. IEEE Sensors Journal 2008, 8, 63-70. 

The main target for microdialysis implantations is the ECF of various organs, predominantly the brain. The main objective of these studies is to find chemical correlations, as represented by measured neurotransmitter levels, to pharmaceutical, behavioral, pathological, or other stimuli. However, because of its small size a microdialysis probe allows sampling of fluids from other locations without first removing the fluid. Body fluids other than ECF to which the microdialysis technique has been applied are considered in Sections 6.3.1.1 to 6.3.I.6. 

The microdialysis technique can be used for continuous in vivo sampling of any body fluid. The main application field of microdialysis is for monitoring the intercellular chemical signaling and transport of molecules in the extracellular fluid. The principle of sampling, based entirely on dialysis (diffusion), ensures that no fluid is removed from or delivered into the sampling area. This principle, together with a fine diameter of the microdialysis cannula, makes it... 

Hamberger A, Jacobson I, Larsson S, Lonnroth P, Nystrom B, Sandberg M (1991) Microdialysis technique for studying brain amino acids in the extracellular fluid Basic and clinical studies. In Microdialysis in the Neurosciences. Techniques in the Behavioral and Neural Sciences, Vol. 7, TE Robinson and JB Justice Jr, Eds., pp. 407-423. Elsevier Sdence Publishers, Amsterdam. 

Kennergren C, Olsson GW, Lonnroth P, Mantovani V, Berggren H, Nystrbm B, NystrOm U, Hamberger A (1994) Microdialysis technique for continuous in vivo surveillence of intramyocardial ischemia. Scand J Thorac Cardiovasc Surg, submitted. 

The microdialysis technique was subsequently adopted by the same groups (such as Pfeiffer and Shichiri) which had initially developed the in vivo needle sensors, now employing these same sensors in a flow system connected to a microdialysis probe for sampling [105-108]. 

By exploiting the microdialysis technique, the miniaturization of the whole instrumentation was achieved, also through the use of a peristaltic pump which turned out to be the only type of pump suitable for coupling to an electrochemical cell. The high sensitiviiy of the latter, in fact, revealed that all the syringe pumps tested were not really pulse-free . 

A completely satisfactory solution to this problem has not been achieved up to now, but attempts at resolution, also in combination with microdialysis techniques, have been reported. 

Since it was found that the thienylethylamine moiety might act as a dopamine receptor pharmacophore, we tested whether a thiophene moiety may act as a bioisostere for a phenol in 2-aminotetralins and hexahydronaphthoxazines. Therefore, thiophene analogues of the 2-aminotetralins and hexahydronaphthoxazines, 34-39 were synthesised. All the compounds synthesised were tested in vitro for their affinity at dopamine D2L and D3 receptors. The derivatives with interesting properties were further investigated for their in vivo dopamine receptor activity and bioavailability using the microdialysis technique in freely moving rats.215... 

In the present study, R-(-)-apomorphine and three of its analogues were studied for their potency in decreasing the release of dopamine in the striatum after subcutaneous administration and for their oral bioavailability using the microdialysis technique in freely moving rats. 

Fleck et al., 1993). This result was also obtained under conditions mimicking high neuronal activity (Szerb, 1988). Also in the intact striatum using the microdialysis technique, a selective increase in Asp release after chemical depolarization (with GABA antagonists or NMDA) of the neocortex has been demonstrated (Palmer et al., 1989). Such selectivity suggests that Asp is released independently of Glu both in brain slices and the intact brain. 

A. Menarini Diagnostics has developed the GlucoDay S semi-invasive continuous glucose monitor, which is based on a microdialysis technique and is specifically for clinical use. 

Poscia A, Mascini M, Moscone D et al. A microdialysis technique for continuous subcutaneous glucose monitoring in diabetic patients (part 1). Biosens Bioelectron 2003 18 891-898. 

Kreilgaard, 2001). The anesthetic effect of the two formulations indicated similar cutaneous absorption profiles of lidocaine from both formulations. Howcvct, a threefold increase in apparent absorption rate and a significant decrease in lag time of lidocaine applied in microemulsion vehicle compared to 5% xylocaine were demonstrated with cutaneous microdialysis. This study illustrated that, compared to the pharmacodynamic model, the microdialysis technique has higher sensitivity and less variability to access bioeqmvalence of topically applied chemicals. 

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