Verapamil plasma concentrations during treatment with cytostatic drugs.

Cytostatic drugs reduce the rate and extent of beta-acetyldigoxin absorption attributable to reversible damage of the gastrointestinal mucosa. As beta-acetyldigoxin verapamil is an agent rapidly absorbed in the proximal small bowel, plasma concentrations and apparent absorption of verapamil administered orally (160 mg) have been determined in nine patients with nongastrointestinal cancer before and 24 h after cytostatic treatment. The cytostatic therapy reduced the area under the plasma verapamil concentration-time curve in eight of the patients, with a mean reduction of 35% (p less than 0.05). It is concluded that, as previously found for digoxin, the absorption of verapamil is diminished owing to impairment of the absorptive capacity of the mucosa of the upper small intestine.