A patient with the Lambert-Eaton syndrome (LES) and small cell lung cancer 
developed respiratory failure several hours after verapamil was given. 
Improvement in respiratory function did not occur when guanidine was given, but 
was delayed until verapamil was discontinued 3 days later. Although other 
factors may have contributed to the clinical deterioration of our patient, the 
temporal relationship to verapamil and the theoretical danger of calcium channel 
blockade lead us to believe that the drug should be used cautiously in LES.