Verapamil augmentation of lithium treatment improves outcome in mania unresponsive to lithium alone: preliminary findings and a discussion of therapeutic mechanisms. - Mallinger, Alan G; Thase, Michael E; Haskett, Roger; Buttenfield, Joan; Luckenbaugh, David A; Frank, Ellen; Kupfer, David J; Manji, Husseini K (Bipolar Disorders, 2008)