Which statement is true regarding the safety of using warfarin compared to penicillin?

The statement regarding warfarin highlights its potential for causing dangerous adverse effects, particularly because it has a narrow therapeutic range. This means that the difference between its effective dose and its toxic dose is small. If the bioavailability of warfarin is altered—due to interactions with other drugs, dietary changes, or changes in health status—there can be significant fluctuations in its anticoagulant effect. Such variations could lead to either inadequate anticoagulation (risking thromboembolic events) or excessive anticoagulation (risking bleeding complications). This characteristic underscores the importance of close monitoring and careful management of warfarin therapy to ensure safety and efficacy.

While both warfarin and penicillin can have adverse effects, the considerations around their therapeutic indices and the consequences of altered bioavailability differ. Warfarin's safety profile necessitates more oversight compared to the generally wider therapeutic index of penicillin, which can accommodate variations in dosing without immediately leading to severe complications.