In a patient receiving dantrolene, calcium channel blockers are contraindicated because of this potential life-threatening effect?
Hyperkalemia and cardiovascular collapse. In an older swine study done by Saltzman LS et al., dantrolene administration in swine pre-treated with verapamil resulted in decreased cardiac function and hyperkalemia. Cardiac arrest occurred in all 5 animals in this study.
Saltzman LS, Kates RA, Corke BC, Norfleet EA, Heath KR. Hyperkalemia and cardiovascular collapse after verapamil and dantrolene administration in swine. Anesthesia and Analgesia. 1984 May;63(5):473-478.