As skin is the outermost covering of the body, primarily functions as a protective layer which protects the individual from the harmful external stimuli like light, temperature, radiation, etc. and restricts the entry of pathogen or any other foreign material inside. Such defensive attribute of skin makes the topical or transdermal drug delivery very difficult. As to improve the drug permeation across the skin and enhance the percutaneous absorption there are various novel strategies which have been adapted including the vehicle system, permeation enhancer, novel drug carrier system, transdermal patches, etc. All these strategies enhance the drug permeation by temporary destructing the stratum corneum layer [20]. The micro emulsion reduces the interfacial tension at the skin surface and solubilizes the drug. The permeation enhancer sometime surfactant or lipid, used in the formulation may dissolve or perturbates the lipid bilayer structure of the stratum corneum. By this way, it minimizes the barrier function of the stratum corneum and opens a pore or passage for drug transfer across skin [2,21].

One of the drug named Levofloxacin can be formulated as a microemulsion as it is FDA-approved for the treatment of various bacterial infections including nosocomial pneumonia, community-acquired pneumonia, acute bacterial rhinosinusitis, acute bacterial exacerbation of chronic bronchitis, acute bacterial prostatitis, acute pyelonephritis, urinary tract infection, skin or skin structure infections, prophylaxis, and treatment of plaque due to Yersinia pestis, and to reduce the incidence of disease progression of inhalational anthrax.

Levofloxacin is a broad-spectrum, third-generation fluoroquinolone antibiotic used to treat bacterial infections. Levofloxacin is a safe and effective medicine on the World Health Organization's essential medicines list. It was patented in 1987 and subsequently received FDA approval in 1996 for medical use in the United States [22].

As a promising anti bacterial agent Levofloxacin directly inhibits bacterial DNA synthesis, promoting the breakage of DNA strands by inhibiting DNA-gyrase in susceptible organisms, which inhibits the relaxation of super coiled DNA. The drug is available both for oral tablets and solution and intravenous administration. Levofloxacin is not available for administration through intramuscular, intrathecal, or subcutaneous routes. The marketed oral dosage strengths for levofloxacin are 250 mg, 500 mg, and 750 mg [23].

Another drug of choice can be Naproxen which is a non-steroidal mitigating medication (NSAID) of the propionic acid class and is generally utilized for help of a wide mixed bag of agony, fever, swelling and solidness [24]. It is the favored NSAID for long haul use in individuals with a high danger of cardiovascular entanglements, it offers a moderate danger of bringing on stomach ulcers as contrasted and ibuprofen, which is okay, and indomethacin, which is high hazard [25]. Keeping in mind the end goal to lessen the danger of stomach ulceration, it is frequently joined with a proton-pump inhibitor (a pharmaceutical that decreases the generation of stomach corrosive) amid long haul treatment.

Naproxen, when given orally can cause gastrointestinal problems, such as heartburn, constipation, diarrhea, ulcers and stomach bleeding. Another disadvantage associated with Naproxen is that it undergoes extensive first pass metabolism due to which high dose has to be administered [26]. This again reduces the patient compliance.

Microemulsions are thermodynamically stable and optically isotropic liquid solutions of oil, water and amphiphile. Microemulsions are one of the best candidates as novel drug delivery system because of their long shelf life, improved drug solubilization with ease of preparation and administration [27]. Therefore, to overcome these disadvantages, it is favorable to administer the drug through an alternative route, which is transdermal route. Microemulsion gels are a type of delivery systems in which the drug can be easily administered and absorbed. Topical microemulsion gel shows controlled drug release property. The microemulsion gel could be an effective alternative vehicle for delivering the drug through topical route to avoid side effects associate with oral route [28]. Moreover, this can be applied at the site of action and thus the dosage form becomes site specific.