Medications That Increase RDW Levels

Chemotherapy and Cancer Treatment Agents

Platinum-based chemotherapy drugs directly induce eryptosis and accelerate red cell turnover, leading to elevated RDW in patients with cancer, particularly those with lung cancer 1
Cytostatic agents worsen anemia with elevated RDW in cancer patients, involving increased heterogeneity of red blood cells due to accelerated turnover and impaired erythropoiesis 1

Nafcillin, when used long-term (>6 weeks), acts as a CYP3A4 and CYP2C9 inducer, potentially affecting red cell parameters, according to the American Heart Association 2
Anti-staphylococcal penicillins, including flucloxacillin and cloxacillin, show similar CYP450 enzyme induction effects during extended treatment courses, which can impact erythrocyte homeostasis 2
Rifampin induces CYP450 enzymes during protracted treatment for conditions like tuberculosis or endocarditis, requiring consideration of its effects on red cell parameters 2

Medications can increase RDW through multiple pathways: inducing eryptosis, causing erythrocyte membrane injury, impairing erythropoiesis, or accelerating red cell destruction, as noted by the American College of Clinical Pharmacology 1

Not all antibiotics increase RDW through enzyme induction—some antibiotics primarily affect other parameters through CYP450 inhibition rather than causing direct RDW elevation, as reported by the American Heart Association 2
The full induction effect of CYP450-inducing antibiotics takes 2-4 weeks to manifest, so RDW changes may be delayed, according to the American College of Clinical Pharmacology 2