Effects of cytostatic drugs on plasma level and renal excretion of β‐acetyldigoxin

Mucosal defects decrease digoxin absorption in patients with malabsorption syndromes. Since the intestinal mucosa can be damaged by cytostatic drugs, we investigated their effects on digoxin plasma levels and urinary digoxin excretion. In six patients with malignant lymphoma who received 0.8 mg β‐acetyldigoxin before and 24 hr after treatment with a combination of cyclophosphamide, oncovin, procarbazine, and prednisone (COPP) or cyclophosphamide, oncovin, and prednisone (COP), plasma digoxin concentrations were measured 0 to 8 hr after the dose and areas under the plasma concentration‐time curves were calculated. In 15 patients on 0.3 mg of β‐acetyldigoxin daily, plasma glycoside concentrations and renal excretion were measured daily before and after COPP, COP, cyclophosphamide, oncovin, cytosine‐arabinosine, and prednisone (COAP), or adriamycin, bleomycin, and prednisone (ABP) treatment schemes. The diminished steady‐state glycoside plasma concentrations and daily renal glycoside excretion during the 24 to 168 hr after the cytostatic drug established reversible impairment of digoxin absorption. The delayed time to peak after a single dose of digoxin during cytostatic drug therapy shows that extent and rate of digoxin absorption are reduced. To maintain adequate control of digoxin therapy in patients treated with cytostatic drugs, plasma levels should be monitored. Clinical Pharmacology and Therapeutics (1981) 30, 518–527; doi: 10.1038/clpt.1981.197