RecruitingDrug trialA Study to Investigate Lithium Brain/Plasma Pharmacokinetics and Safety of an AL001 Oral Capsule Compared to a Marketed Immediate-release Lithium Carbonate Capsule in Subjects With Bipolar I DisorderThe goal of this clinical trial is to assess the safety and effects of a crystallized form of lithium, AL001, when compared to commonly used lithium carbonate in individuals diagnosed with bipolar I disorder. The main questions this study aims to answer are: * How safe is AL001 when compared to lithium carbonate? * How is AL001 broken down in the brain and body compared to lithium carbonate? Participants will be asked to: * Take both the study drug (AL001) and lithium carbonate each for a period of 14 days. * Stay overnight at MGH's research unit for two separate 2-week periods. * Participate in two separate 24 hour periods of multiple MRIs and blood draws.