Interactions between calcium channel blockers and the anticonvulsants carbamazepine and phenytoin

Bahls, Fredrick H. MD, PhD
Ozuna, Judy RN, MN
Ritchie, Deanna E. RN, MN

From the Departments of Medicine (Neurology) (Dr. Bahls and J. Ozuna), Rehabilitative Medicine (D.E. Ritchie), and Physiology and Biophysics (Dr. Bahls), University of Washington School of Medicine and Seattle Veterans Administration Medical Center, Seattle, WA.

This work was supported in part by a Clinical Investigator Award to F.H.B. (NIH NS01167).

Presented in part at the 42nd annual meeting of the American Academy of Neurology, Miami Beach, FL, April 1990.

Received July 25, 1990. Accepted for publication in final form October 12, 1990.

Address correspondence and reprint requests to Dr. F.H. Bahls, Department of Zoology and Genetics, Science II, Iowa State University, Ames, IA 50011.

Neurology 41(5):p 740-742, May 1991.

Article abstract

We describe a retrospective analysis of the frequency of adverse interactions between calcium channel blockers and anticonvulsant drugs (phenytoin and carbamazepine) in a series of 43 patients. Ten patients receiving carbamazepine and three patients receiving phenytoin exhibited symptoms or signs of toxicity. Toxicity occurred with both diltiazem and verapamil, but not with nifedipine. These results emphasize the need for careful clinical and laboratory monitoring of patients receiving both classes of medication.

NEUROLOGY 1991;41:740-742