CALCIUM-CHANNEL BLOCKERS AND THEOPHYLLINE

Giving calcium-channel blockers to patients taking theophylline normally has no adverse effect on the control of asthma, despite the small or modest alterations that occur in theophylline levels with diltiazem, felodipine, nifedipine and verapamil. However, there are isolated case reports of unexplained theophylline toxicity in 2 patients given nifedipine and 2 patients given verapamil.
The clinical significance of the cases is unclear, but generally no adverse interaction would be expected.