Aspirin is recommended as first-line antiplatelet drug for all types of acute disease that causes the blood vessels thrombotic in cardiovascular disease. Orally adminestered aspirin has side effects on the risk of gastrointestinal bleeding, and is presistemic metabolism in the gastrointestinal and liver. Transdermal delivery offers an alternative for adminestering aspirin that bypasses the gut and may be a more convenient and safer for long-term use. This study used form of microemulsion to prevent hydrolysis of aspirin, because it contains a high enough concentration of surfactant. Microemulsion is a dosage form  can penetrate for transdermal delivery. This research purpose to know the effect of tween 80 and propylene glycol as surfactant and cosurfactant to the physical stability of the microemulsion. The variation used of tween 80 and propylene glycol (2:1) and 54%, 57%, 60% and 63%, then the physical stability testing for 6 weeks. The results that formula showed, and  60% of tween 80 and propylene glycol (2:1) provide the most stable formula. Formula F3 showed the following results, pH of 3.74 ± 0.30, viscosity of 1198.76 ± 56.02 Cps, BJ of 1.0669 ± 0.005 g/mL, the surface tension of 38.77 ± 0.43 dyne/cm and a particle size of 49.46 ± 6.91 nm. The concluded that the optimum concentration of tween 80 as surfactant and cosurfactant propilenglikol with ratio (2:1) is F3 with concentration of 60%.

Keywords: Aspirin, Transdermal, microemulsion, surfactant