**4.4 Topical route**

Topical route is one of the alternative approaches over the oral and parenteral route. This is one of the non-invasive methods of drug delivery system [65]. They are also convenient route of drug delivery. They are also helpful in overcoming various limitations that are being produced by oral route like gastrointestinal degradation of drug, hepatic clearance, toxicity and finally decreased bioavailability. Though the topical route have several advantages, they also have certain disadvantages like low permeability though the skin, decreased residence time on skin, the viscosity of the formulation, spreadability of the formulation etc. But these problems can be conquered with the aid of microemulsion. They have the capacity to permeate through the skin, improve the solubility of the drug and also enhance the absorption of the drug. Various drugs are being incorporated into the microemulsion because of these properties [66]. Example Methyl dihydrojasmonate that has the capacity to produce anti-tumor activity is being incorporated into microemulsion and studied. Targeting solid tumors by transdermal delivery is in emerging stage. This allows convenient way of targeting the tumor and also overcome the first pass metabolism produced by the oral dosage forms. The Methyl dihydrojasmonate that has been incorporated in microemulsion has been studied on MCF-7 cancer cell and Ehrlich solid carcinoma model [67].

The non-toxic and non-irritant property of microemulsion makes them suitable to treat skin cancers. 5- Fluorouracil has been used for treating skin cancer. But they have a major disadvantage of poor skin permeation. Thus, in this case they are being incorporated into microemulsion for improving the permeability of the drug. So that it can produce its anti-cancer activity [68]. 5-fluorouracil is being studied by many of the researchers by incorporating them into a microemulsion for rehabilitation of skin cancer [69]. Thus, opting for a microemulsion would be a good strategy for the treatment of skin cancer and solid tumors.

Apart from the microemulsion, the incorporation of microemulsion into gel also plays a vital role. It further increases the residence time of the drug on the skin and also release of the drug on the target site is prolonged [70].


**Table 3.**

*Various microemulsions with different drug, oil, surfactant and co-surfactant are given.*

Some other microemulsions that are studied by various researchers for anticancer activity is given in **Table 3**.
