Lidocaine hydrochloride/prilocaine

LroOCAINE HYDROCHLORIDE/PRILOCAINE (EMLA cream, 2.5% lidocaine and 2.5% prilocaine)... 

Lidocaine is a local anaesthetic which is available as a free base and hydrochloride salt. Lidocaine base is known to form eutectic mixture with prilocaine base and this eutectic mixture forms a dispersed phase of EMLA emulsion cream. Shukla et al. reported that with the help of microemulsification, the drug loading can be increased from 5% (present in EMLA cream) to 20% which may result in quick action by virtue of higher concentration gradient across the skin [49]. 

It is a local anaesthetic of the amide type which is employed for surface, infiltration and nerve block anaesthesia. Its duration of action is in between the shorter-acting lidocaine and longer-acting mepivacaine. It possesses less vaso-dilator activity than lidocaine and hence may be used without adrenaline. Therefore, solutions of prilocaine hydrochloride are specifically beneficial for such patients who cannot tolerate vasopressor agents patients having cardiovascular disorders, diabetes, hypertension and thyrotoxicosis. 

Lidocaine showed slow diffusion in all ME systems suggesting association with the lipophilic phase. Prilocaine hydrochloride also showed slow diffusion behavior and the authors explained this by association of the drug with the surfactant... 

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