科研之友
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摘要
Part 2 of this paper deals with the techniques for drug delivery of topical and injectable local anaesthetics. The various routes of local anaesthetic delivery (epidural, peripheral, wound catheters, intra-nasal, intra-vesical, intra-articular, intra-osseous) are explored. To enhance transdermal local anaesthetic permeation, additional methods to the use of an eutectic mixture of local anaesthetics and the use of controlled heat can be used. These methods include iontophoresis, electroporation, sonophoresis, and magnetophoresis. The potential clinical uses of topical local anaesthetics are elucidated. Iontophoresis, the active transportation of a drug into the skin using a constant low-voltage direct current is discussed. It is desirable to prolong local anaesthetic blockade by extending its sensory component only. The optimal release and safety of the encapsulated local anaesthetic agents still need to be determined. The use of different delivery systems should provide the clinician with both an extended range and choice in the degree of prolongation of action of each agent. 1. Introduction A drug delivery system should have minimal tissue reaction, a reliable drug release profile, and well-defined degradation rate for biodegradable carrier until all nontoxic products are excreted [1]. For local anaesthetics (LAs), the development of new effective delivery systems intends to suitably modulate the release rate of these drugs, extend their anaesthetic effect, and enhance their localisation; this reduces problems of systemic toxicity. Part 2 of this paper deals with the innovations pertaining to formulations, and techniques for drug delivery of topical and injectable local anaesthetics. 2. Routes of Local Anaesthetic Delivery 2.1. Epidural Patient controlled epidural analgesia (PCEA) allows patients to self-administer drug doses according to their analgesic needs. This route relies on a staff-programmed pump and skilled and qualified members of the hospital staff for administration. Both local anaesthetics and opioids are agents for epidural analgesia. The use of epidural local anaesthetics is associated with a higher incidence of hypotension, motor block, and urinary retention, compared with use of opioids [2]. However, in a recent meta-analysis, only a continuous infusion of epidural local anaesthetics was superior to intravenous opioids in improving pain control and reducing adverse effects [3]. 2.2. Peripheral Patient-controlled regional analgesia (PCRA) encompasses a variety of techniques that provide effective postoperative pain relief without
