The aim of this study is to investigate the phytotoxic effects of six most common pharmaceuticals exposed at four concentrations in bioassays. The pharmaceuticals presented are classified as five antibiotics and one anticonvulsant drug. Toxicity tests were carried out using diluted model wastewater to evaluate the toxic potential using Lactuca sativa as bioindicator. The highest inhibition effect was observed in the range of 0.1 to 1000 mg L-1. Lactuca sativa L. seeds were used for this study and germination percentage, sprout and root length were evaluated. All the formulations used in this bioassay had inhibitory effects on root growth, radicle and hypocotyl elongation, and germination of Lactuca sativa seeds. The results showed that in tests with Lactuca sativa seeds, Sulfamethoxazole (SMZ) 8.6% and Trimethoprim (TMP) 3.2% at 0.1 mg L-1 dilution showed the least inhibition, while Tetracycline (TC) at concentrations of 500 and 1000 mg L-1 was fatal to Lettuce seeds. Overall, this study emphasizes the importance of proper disposal of water containing antibiotics as a strong exposure factor for biological organisms.