Nanoemulsions have attracted great attention in research, dosage form design and pharmacotherapy. This is as a result of a number of attributes peculiar to nanoemulsions such as optical clarity, ease of preparation, thermodynamic stability and increased surface area. Nanoemulsions also known as submicron emulsions serve as vehicles for the delivery of active pharmaceutical ingredients as well as other bioactives. They are designed to address some of the problems associated with conventional drug delivery systems such as low bioavailability and noncompliance. The importance of design and development of emulsion nanocarrier systems aimed at controlling and/or improving required bioavailability levels of therapeutic agents cannot be overemphasized. Reducing droplet sizes to the nanoscale leads to some very interesting physical properties, such as optical transparency and unusual elastic behaviour. This review sheds light on the current state of nanoemulsions in the delivery of drugs and other bioactives. The morphology, formulation, characteristics and characterization of nanoemulsions were also addressed.

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Current State of Nanoemulsions in Drug Delivery

Many advantages of gels a major limitation is in the delivery of hydrophobic drugs. So to overcome this limitation an emulsion based approach is being used so that even a hydrophobic therapeutic moiety can enjoy the unique properties of gels. When gels and emulsions are used in combined form the dosage form are referred as emulgel. In recent years, there has been great interest in the use of novel polymers. A unique aspect of dermatological pharmacology is the direct accessibility of the skin as a target organ for diagnosis and treatment. The combination of hydrophilic cornified cells in hydrophobic intercellular material provides a barrier to both hydrophilic and hydrophobic substances. Within the major group of semisolid preparations, the use of transparent gels has expanded both in cosmetics and in pharmaceutical preparations. Polymer can function as emulsifiers and thickeners because the gelling capacity of these compounds allows the formulation of stable emulsions and creams by decreasing surface and interfacial tension and at the same time increasing the viscosity of the aqueous phase. In fact, the presence of a gelling agent in the water phase converts a classical emulsion into an emulgel. These emulgel are having major advantages on novel vesicular systems as well as on conventional systems in various aspects. Various permeation enhancers can potentiate the effect, So emulgels can be used as better topical drug delivery systems over present systems. The use of emulgels can be extended in analgesics and antifungal drugs.

Emulgel: a review

Utilising nanoemulsions as vehicles for carrying active pharmaceutical ingredients is emerging as a promising approach for the latters’ targeted delivery. For drug molecules to be clinically effective, their administration by a route, which provides a proper channel for them to reach their target, is of prime importance. Further, they also need to be suitably protected in the biological milieu till they are delivered to the required site of action. Nanoemulsions with a mean droplet diameter of about 20-200 nm are extremely versatile in this regard. Due to their characteristic size and properties, which includes kinetic stability, they are very effective in enveloping and/or solubilising the drugs and successfully chaperoning them towards suitable targets. They also cause the drugs to be released  in controlled and sustained modes, thereby reducing drug toxicity and dumping. Additionally, depending on the physiochemical properties of the drugs, nanoemulsions can be structurally engineered to maximize their solubilisation as per the required route of delivery, which is heavily dependent on the drug structure. Effective targeting can be achieved by incorporating suitable homing molecules on their surface, which in turn  recognize and bind to specific receptors on the target molecules. This review focuses on the different routes by which drug loaded  nanoemulsions can be administered, thus throwing light on the versatility of these vehicles for therapeutic and other related applications.

Nanoemulsions for drug delivery through different routes

A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream. Often, this promotes healing to an injured area of the body. An advantage of a transdermal drug delivery route over other types of medication delivery such as oral, topical, intravenous, intramuscular, etc. is that the patch provides a controlled release of the medication into the patient, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. The main disadvantage to transdermal delivery systems stems from the fact that the skin is a very effective barrier; as a result, only medications whose molecules are small enough to penetrate the skin can be delivered in this method. A wide variety of pharmaceuticals are now available in transdermal patch form.

https://thepharmajournal.com/vol1Issue4/Issue_june_2012/14.pdf

Transdermal Drug Delivery System: A Review

Transdermal drug delivery system was introduced to overcome the difficulties of drug delivery through oral route. A transdermal patch is medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream. Often, this promotes healing to an injured area of the body. An advantage of a transdermal drug delivery route over other types of medication delivery such as oral, topical, intravenous, intramuscular, etc. is that the patch provides a controlled release of the medication into the patient, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. The main disadvantage to transdermal delivery systems stems from the fact that the skin is a very effective barrier; as a result, only medications whose molecules are small enough to penetrate the skin can be delivered in this method. This review article describes the methods of preparation of different types of transdermal patches such as matrix patches, reservoir type, membrane matrix, drug-in-adhesive patches and micro reservoir patches. In addition, the various methods of evaluation of transdermal dosage form have also been reviewed.

Transdermal patches: a recent approch to new drug delivery system

Various new technologies have been developed for the transdermal delivery of some important drugs. Physical and chemical means of crossing the lipophilic stratum corneum, the outermost layer of the skin, are being explored. A thorough understanding of skin physiology and the basics behind the new technologies would be useful for understanding these exciting new drug delivery systems. Alternative techniques of physical sciences including electrical signals, ultrasonic and laser radiations are being used to facilitate delivery of drugs across the epidermal barrier. Several approaches in form of carriers/ vehicles are also being developed for efficient delivery of drugs. Another major concern is regulatory issues of transdermal products to be launched in the market. This review deals with a brief insight on physiological properties of the skin, several techniques for drug permeation enhancement and regulatory issues over transdermal drug delivery.

K. Dave

Papers

Transdermal drug delivery system: a review