<prompt> Answer this question truthfullyWhat is the potential risk associated with thymidine synthesis inhibitor use, particularly with MTX, 5-FU, and hydroxyurea, and how does it relate to their mechanism of action?  <response>: <reason> Thymidine synthesis inhibitor use can result in an increased risk for infection due to immunosuppression. This is because these drugs target rapidly dividing cells, including immune cells, leading to a weakened immune system. 