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Verapamil plasma concentrations during treatment with cytostatic drugs
Abstract:
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.
Insights
Cytostatic drugs impair the absorption of verapamil, a medication commonly used for heart conditions. This study found a significant reduction in verapamil absorption after cancer treatment, impacting its effectiveness.
Area of Science:
- Pharmacology
- Gastroenterology
- Oncology
Background:
- Cytostatic drugs are known to affect gastrointestinal (GI) mucosa integrity.
- Previous studies indicated that cytostatic agents reduce the absorption of beta-acetyldigoxin.
- Verapamil is a calcium channel blocker rapidly absorbed in the upper small intestine.
Purpose of the Study:
- To investigate the impact of cytostatic therapy on the oral absorption of verapamil.
- To determine if cytostatic drugs affect verapamil plasma concentrations and absorption rates.
Main Methods:
- Nine patients with non-gastrointestinal cancer were enrolled.
- Oral verapamil (160 mg) absorption was measured before and 24 hours after cytostatic treatment.
- Plasma verapamil concentrations were analyzed to calculate the area under the concentration-time curve (AUC).
Main Results:
- Cytostatic therapy led to a mean reduction of 35% in the AUC of plasma verapamil.
- This reduction was statistically significant (p < 0.05) and observed in eight out of nine patients.
- The findings suggest impaired verapamil absorption following cytostatic treatment.
Conclusions:
- Cytostatic drugs diminish verapamil absorption, similar to their effect on digoxin.
- The impairment is attributed to reversible damage to the upper small intestine's mucosal absorptive capacity.
- Clinical implications include potential need for dosage adjustments or alternative administration routes for verapamil during cytostatic therapy.