Plastic has a very important function in people's daily lives. Due to its good properties, such as low cost and high usability, it is becoming a key material today and is used to make packaging, medical supplies, vehicle parts, etc. However, poor plastic waste management leads to the formation of microplastics which become one of the main pollutants in aquatic ecosystems. Also, the problem in aquatic ecosystems is posed by pharmaceuticals, representatives of the group of "new pollutants". Due to the growing need for use, they reach in the environment in various ways. One of the most commonly detected pharmaceuticals in the environment is diclofenac (DCF). Pharmaceuticals can adsorb to the surface of microplastics and thus enter the food chain and cause even greater problems for the environment and human health. The aim of this work was to investigate the influence of microplastic particle type and size on pharmaceutical adsorption. The plastic was previously exposed to combined aging under the influence of heat and UV radiation for 14, 28 and 42 days. Using the method of response surfaces, it was examined the influence of different process parameters and the degree of age of microplastics on the response of the adsorption process. Under conditions under which is reached the maximum degree of adsorption, it were examined the kinetics of the process and the thermodynamic aspect was included in the determination of adsorption isotherms. Furthermore, it has been proposed an adsorption mechanism with respect to the previously performed characterization of microplastic surface samples. Finally, it was performed the toxicity testing of the samples to determine the harmfulness of system with microplastic and pharmaceuticals on living beings. It was found that materials that are longest exposed to aging degrade more easily, and the result is the largest amount of particles of the smallest dimensions compared to samples that are less exposed to aging. It was also found that the maximum response was achieved by applying the material that was longest exposed to aging. Thermodynamic parameters indicate that the adsorption process in both cases (bottles and foils) is spontaneous and that it is physisorption. The toxicity test determined that the MP + DCF system is more toxic than DCF itself and that the bottle sample inhibits the growth of microalgae to a greater extent than the foil sample.